1import{_ as e,c as r,e as d,o as a}from"./app-CjUkjRdW.js";const o={};function n(i,t){return a(),r("div",null,t[0]||(t[0]=[d('<h1 id="computing-acronyms" tabindex="-1"><a class="header-anchor" href="#computing-acronyms"><span>Computing Acronyms</span></a></h1><p>Acronyms common in computing, hacker culture, and everyday software engineering conversations. This section collects concise definitions and quick examples to help you grok the jargon fast. A note about the legacy/historical subsections:</p><ul><li><strong>Legacy</strong>: outdated but still in use.</li><li><strong>Historical</strong>: obsolete, mostly of historical interest.</li></ul><div class="acronyms"><h2 id="software-architecture" tabindex="-1"><a class="header-anchor" href="#software-architecture"><span>Software Architecture</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>C4</td><td>ContextâContainerâComponentâCode â lightweight hierarchical diagramming model for communicating software architecture at multiple levels of abstraction.</td><td>Draw a system Context and Container diagram for a web app; break a service into Components; optionally add Code-level diagrams.</td></tr><tr><td>CQRS</td><td>Command Query Responsibility Segregation â separate writes/reads.</td><td>Write model emits events; read model is a projection.</td></tr><tr><td>ECS</td><td>Entity Component System â decompose game and simulation logic into data-only components processed by systems operating on matching entities.</td><td>Game engine with <code>Position</code>/<code>Velocity</code> components updated by a <code>PhysicsSystem</code>; rendering system consumes <code>Mesh</code> components.</td></tr><tr><td>EDA</td><td>Event-Driven Architecture â async event-based systems.</td><td>Publish domain events to Kafka; services react.</td></tr><tr><td>ES</td><td>Event Sourcing â persist state changes as an appendâonly log of events and rebuild current state by replaying them.</td><td>Order aggregate applies <code>OrderPlaced</code>/<code>ItemAdded</code> events; projections update read models.</td></tr><tr><td>SOA</td><td>Service-Oriented Architecture â collaborating services.</td><td>Decompose monolith into services.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>COM</td><td>Component Object Model â Microsoft binary-interface standard for reusable components with reference counting and interface-based polymorphism.</td><td>Query <code>IUnknown</code>/<code>
1IDispatch</code>; register COM servers; Office automation via COM.</td></tr><tr><td>COM+</td><td>Component Services â evolution of COM/DCOM on Windows that adds declarative transactions, role-based security, queued components, and pooled object activation managed by the OS.</td><td>Configure COM+ applications in Component Services MMC; legacy enterprise apps use COM+ transactions and queued components before .NET.</td></tr><tr><td>DCOM</td><td>Distributed COM â extension of COM for inter-process and cross-machine communication using RPC.</td><td>Remote COM server activation/config over the network using DCOMCNFG.</td></tr><tr><td>DDE</td><td>Dynamic Data Exchange â legacy Windows message-based mechanism for applications to exchange data and commands via shared memory conversations; superseded by OLE/COM automation.</td><td>Early Windows apps used DDE for live spreadsheet/word processor links; replaced by OLE automation and modern IPC.</td></tr><tr><td>EJB</td><td>Enterprise JavaBeans â server-side component model for building distributed, transactional applications in Java; heavyweight and largely superseded by lighter frameworks.</td><td>Session Beans, Entity Beans, MDBs in a Java EE/Jakarta EE application server.</td></tr><tr><td>ESB</td><td>Enterprise Service Bus â centralized integration/message bus with mediation, routing, and governance typical of classic SOA; considered heavyweight today.</td><td>Hubâandâspoke integration; replaced by microservices and event streaming (Kafka).</td></tr><tr><td>MAPI</td><td>Messaging Application Programming Interface â Windows component API for email, calendaring, and messaging integration, primarily used by Microsoft Exchange/Outlook clients.</td><td>Outlook talks to Exchange via Extended MAPI; legacy apps used Simple MAPI to open/send mail through the default client.</td></tr><tr><td>MOM</td><td>Message-Oriented Middleware â infrastructure for asynchronous communication between distributed systems via messages and queues, decoupling producers and consumers.</td><td>IBM MQ, TIBCO, MSMQ; modern equivalents include Kafka and RabbitMQ.</td></tr><tr><td>MSMQ</td><td>Microsoft Message Queuing â durable asynchronous messaging middleware built into Windows that provides store-and-forward queues with transactional and secure delivery.</td><td>Legacy enterprise apps used MSMQ to decouple services; integrates with COM+, WCF, and bridge adapters for REST/HTTP.</td></tr><tr><td>OCX</td><td>OLE Control Extension â a legacy Microsoft standard for reusable software components based on COM/OLE, the predecessor to ActiveX controls.</td><td>Embedding third-party UI controls (<code>.ocx</code> files) in Visual Basic 6 applications.</td></tr><tr><td>SOAP</td><td>XML-based messaging protocol for web services.</td><td>Enterprise integrations over SOAP.</td></tr><tr><td>WCF</td><td>Windows Communication Foundation â a legacy .NET framework for building service-oriented applications.</td><td>Superseded by gRPC and ASP.NET Core Web API.</td></tr><tr><td>WF</td><td>Windows Workflow Foundation â a legacy .NET framework for building workflow-based applications.</td><td>State machine or sequential workflows in older .NET applications.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>CORBA</td><td>Common Object Request Broker Architecture â OMG standard for language- and platform-neutral distributed objects communicating via an Object Request Broker.</td><td>Define interfaces in IDL; ORB uses IIOP for interop between stubs and skeletons.</td></tr><tr><td>DCE</td><td>Distributed Computing Environment â OSF framework for distributed applications providing RPC, security (Kerberos), directory, and threading services.</td><td>Build client/server apps with DCE RPC; secure with GSSAPI; use CDS for naming.</td></tr></tbody></table><h2 id="software-design" tabindex="-1"><a class="header-anchor" href="#software-design"><span>Software Design</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AoS</td><td>Array of Structs â contiguous collection where each element stores all fields, offering good spatial locality for per-entity operations.</td><td><code>struct Particle { float x, y, z; } particles[N];</code> iterate once to update position/velocity.</td></tr><tr><td>CPS</td><td>Continuation-Passing Style â express control flow by passing an explicit continuation function instead of returning normally.</td><td><code>f(x, k)</code> calls <code>k(result)</code>; enables tail calls, trampolines, async composition.</td></tr><tr><td>CSP</td><td>Communicating Sequential Processes â formal concurrency model where independent processes interact solely via messageâpassing over channels (no shared memory).</td><td>Go channels/<code>select</code> and occam are CSPâinspired; model systems as processes and rendezvous on channels.</td></tr><tr><td>DDD</td><td>Domain-Driven Design â model around the domain.</td><td>Ubiquitous language in code and docs.</td></tr><tr><td>DI</td><td>Dependency Injection â provide dependencies from the outside rather than creating them inside.</td><td>Pass a <code>Logger</code> to a service constructor instead of instantiating it.</td></tr><tr><td>DIP</td><td>Dependency Inversion Principle â depend on abstractions, not concretions.</td><td>Accept a <code>Logger</code> interface, not a concrete <code>ConsoleLogger</code>.</td></tr><tr><td>DRY</td><td>Don't Repeat Yourself â avoid duplicating knowledge in code and docs.</td><td>Extract a function instead of pasting the same block twice.</td></tr><tr><td>DTO</td><td>Data Transfer Object â simple data container.</td><td>Map entities to DTOs for API responses.</td></tr><tr><td>FRP</td><td>Functional Reactive Programming â model timeâvarying values and event streams with functional operators.</td><td>UI state as RxJS Observables using <code>map/merge/switchMap</code>.</td></tr><tr><td>ISP</td><td>Interface Segregation Principle â prefer many small, clientâspecific interfaces.</td><td>Use <code>Readable</code>/<code>Writable</code> instead of a bloated <code>File</code> interface.</td></tr><tr><td>KISS</td><td>Keep It Simple, Stupid â prefer simple solutions that meet requirements.</td><td>Use a plain function instead of a custom class hierarchy.</td></tr><tr><td>LSP</td><td>Liskov Substitution Principle â subtypes must be substitutable for their base.</td><td>A subclass shouldn't strengthen preconditions or weaken postconditions.</td></tr><tr><td>MVC</td><td>ModelâViewâController â separate data, presentation, and control flow.<
1/td><td>Controllers orchestrate; Views render; Models hold domain data.</td></tr><tr><td>MVVM</td><td>ModelâViewâViewModel â bind UI to a ViewModel that exposes state/actions.</td><td>Two-way binding in front-end frameworks.</td></tr><tr><td>OCP</td><td>Open/Closed Principle â open for extension, closed for modification.</td><td>Add a new strategy class instead of editing a switch.</td></tr><tr><td>SDI</td><td>Single-Document Interface â application model where each document is opened in its own separate top-level window.</td><td>Web browsers, VS Code; each window is an independent instance.</td></tr><tr><td>SoA</td><td>Struct of Arrays â layout that keeps each field in its own contiguous array to enable SIMD/vectorization and cache-friendly columnar processing.</td><td>Separate <code>x[N]</code>, <code>y[N]</code>, <code>z[N]</code> arrays for particles to update components with wide vector loads.</td></tr><tr><td>SoC</td><td>Separation of Concerns â isolate responsibilities into distinct modules.</td><td>Keep validation, business logic, and persistence in separate layers.</td></tr><tr><td>SOLID</td><td>Five OO design principles: SRP, OCP, LSP, ISP, DIP.</td><td>Extract interfaces and inject dependencies via constructors.</td></tr><tr><td>SRP</td><td>Single Responsibility Principle â one reason to change.</td><td>Split parsing and rendering into separate classes.</td></tr><tr><td>UML</td><td>Unified Modeling Language â notation to visualize/design systems.</td><td>Class and sequence diagrams for architecture and behavior.</td></tr><tr><td>WET</td><td>Write Everything Twice â tongue-in-cheek opposite of DRY.</td><td>Duplicate code rather than refactor.</td></tr><tr><td>WIMP</td><td>Windows, Icons, Menus, Pointer â classic graphical user interface paradigm built around overlapping windows, iconography, menu bars, and a pointing device.</td><td>Xerox Star and Apple Macintosh popularized WIMP desktops; modern desktop OSes retain the model.</td></tr><tr><td>YAGNI</td><td>You Aren't Gonna Need It â don't build features until necessary.</td><td>Skip a caching layer until profiling shows the need.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>MDI</td><td>Multiple-Document Interface â application model where multiple child windows are contained within a single parent window.</td><td>Classic desktop apps (early Photoshop/Office); child windows for each document.</td></tr></tbody></table><h2 id="software-engineering" tabindex="-1"><a class="header-anchor" href="#software-engineering"><span>Software Engineering</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>BDD</td><td>Behavior-Driven Development â specify behavior in examples (Given/When/Then).</td><td>Feature files drive implementation and acceptance tests.</td></tr><tr><td>BDUF</td><td>Big Design Up Front â invest in upfront architecture/design before implementation.</td><td>Comprehensive UML/specs prior to coding (vs iterative/agile).</td></tr><tr><td>CD</td><td>Continuous Delivery/Deployment â automated release pipeline to ship safely.</td><td>Tagging main triggers a production deploy.</td></tr><tr><td>CI</td><td>Continuous Integration â frequently merge to main with automated tests.</td><td>Every PR runs unit and integration tests in CI.</td></tr><tr><td>CI/CD</td><td>Combined practice of Continuous Integration and Delivery/Deployment.</td><td>Build, test, artifact, deploy stages in one pipeline.</td></tr><tr><td>DSC</td><td>Desired State Configuration â declarative configuration management approach that defines the target state and lets tooling converge systems to it continually.</td><td>PowerShell DSC or Azure Automanage enforces web server configs by applying declarative manifests and reporting drift.</td></tr><tr><td>DX</td><td>Developer Experience â overall quality of tools, workflows, and docs that make developers productive and happy.</td><td>Oneâcommand setup, fast feedback loops, clear errors, great CLIs.</td></tr><tr><td>E2E</td><td>End-to-End â tests or flows that cover the full user journey across systems and components.</td><td>Cypress/Playwright tests from UI through API to DB.</td></tr><tr><td>EOL</td><td>End Of Life â product/version no longer supported with fixes or updates; plan upgrades before EOL to remain secure and compliant.</td><td>Ubuntu 20.04 reaches EOL â migrate to 22.04 LTS.</td></tr><tr><td>GA</td><td>General Availability â broad production release status following beta/RC; officially supported.</td><td>Mark v1.0 as GA and enable default rollout.</td></tr><tr><td>HCI</td><td>Human-Computer Interaction â discipline focused on designing, evaluating, and implementing user interfaces and human-centered systems.</td><td>Usability studies, prototyping flows, accessibility reviews for a new feature.</td></tr><tr><td>I18N</td><td>Internationalization â design for multiple languages/locales.</td><td>Externalize strings; ICU formatting; locale-aware dates/numbers.</td></tr><tr><td>ICU</td><td>International Components for Unicode â a mature and widely used set of C/C++ and Java libraries for Unicode support, internationalization, and globalization.</td><td>
1Use ICU for collation, date/time formatting, and character set conversion.</td></tr><tr><td>KPI</td><td>Key Performance Indicator â metric tracking performance toward a goal.</td><td>Conversion rate, p95 latency, crash-free sessions.</td></tr><tr><td>L10N</td><td>Localization â adapt an internationalized product for a locale.</td><td>Translate resources; RTL layout; localized units/images.</td></tr><tr><td>LTS</td><td>Long-Term Support â release line maintained with security/critical fixes for an extended period.</td><td>Choose Node.js LTS for production; receive patches without feature churn.</td></tr><tr><td>MQ</td><td>Merge Queue â automation that sequences merges and runs required checks on up-to-date commits so main stays green.</td><td>GitHub/GitLab merge queue rebases the next PR onto main, runs CI, and auto-merges when green.</td></tr><tr><td>MVP</td><td>Minimum Viable Product â smallest thing to deliver value/learning.</td><td>Ship a CLI prototype before a full GUI.</td></tr><tr><td>OKR</td><td>Objectives and Key Results â align goals and track outcomes.</td><td>Company-level objectives with measurable KRs.</td></tr><tr><td>PoC</td><td>Proof of Concept â quick prototype to validate feasibility.</td><td>Spike code to test a new database driver.</td></tr><tr><td>PR</td><td>Pull Request â propose code change for review/merge.</td><td>Open a PR for CI checks and team review.</td></tr><tr><td>QA</td><td>Quality Assurance â practices to ensure product quality via process and testing.</td><td>Test plans, manual/exploratory testing, and sign-off before release.</td></tr><tr><td>RAD</td><td>Rapid Application Development â iterative, prototypingâfocused approach emphasizing quick delivery and user feedback over heavy upfront planning.</td><td>Build a working prototype with lowâcode/4GL tools and iterate with users.</td></tr><tr><td>RC</td><td>Release Candidate â build believed to be releaseâready, pending final validation.</td><td>Ship RC to staging for UAT and smoke tests.</td></tr><tr><td>RFC</td><td>Request For Comments â proposal/spec for feedback before adoption.</td><td>RFC for a breaking API change.</td></tr><tr><td>SCM</td><td>Source Control Management â processes/tools for tracking changes to source code and related assets; often used interchangeably with VCS.</td><td>Git as an SCM; branching strategies, code reviews, and CI integration.</td></tr><tr><td>SDLC</td><td>Software Development Life Cycle â structured process for planning, designing, building, testing, deploying, and maintaining software.</td><td>Phases: requirements â design â implementation â testing â deployment â maintenance.</td></tr><tr><td>SWE</td><td>Software Engineer â practitioner who designs, builds, tests, and maintains software systems.</td><td>Fullâstack SWE implementing features, writing tests, and doing code reviews.</td></tr><tr><td>TDD</td><td>Test-Driven Development â write a failing test, pass it, refactor.</td><td>Red â Green â Refactor per behavior.</td></tr><tr><td>UAT</td><td>User Acceptance Testing â end users validate requirements.</td><td>Business stakeholders test before release.</td></tr><tr><td>UI</td><td>User Interface â the visual and interactive surface users operate.</td><td>Screens, components, and controls in web/mobile apps.</td></tr><tr><td>UX</td><td>User Experience â usability and satisfaction.</td><td>Research, UX writing, usability testing.</td></tr><tr><td>VCS</td><td>Version Control System â track changes to code and collaborate.</td><td>Git (branches, commits, PRs), Mercurial.</td></tr><tr><td>WIP</td><td>Work In Progress â items in progress; limit to improve flow.</td><td>Cap WIP per Kanban column.</td></tr><tr><td>XP</td><td>Extreme Programming â agile practices emphasizing feedback/simplicity.</td><td>Pair programming, CI, refactoring, and TDD.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>CVS</td><td>Concurrent Versions System â an early, influential client-server version control system that popularized features like branching and merging.</td><td>Superseded by Subversion (SVN) and later Git.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>Y2K</td><td>Year 2000 problem â class of bugs related to storing years with two digits, causing issues with dates in and after the year 2000.</td><td>Remediation projects to expand date fields and fix date logic.</td></tr></tbody></table><h2 id="web-development" tabindex="-1"><a class="header-anchor" href="#web-development"><span>Web Development</span></a></h2><table><thead><tr><th>
1Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AJAX</td><td>Asynchronous JavaScript and XML â async HTTP from the browser.</td><td>Fetch data without full page reload.</td></tr><tr><td>ARIA</td><td>Accessible Rich Internet Applications â a W3C specification for making web content and applications more accessible to people with disabilities.</td><td>Use <code>role="button"</code> and <code>aria-label</code> to make a <code><div></code> accessible as a button.</td></tr><tr><td>ASGI</td><td>Asynchronous Server Gateway Interface â the modern, async-capable successor to WSGI for Python web applications.</td><td>Run a FastAPI or Django 3+ app with Uvicorn.</td></tr><tr><td>ASP.NET</td><td>Active Server Pages .NET â Microsoft's web application framework for building dynamic web sites and services with languages like C#.</td><td>Build web APIs and Razor Pages with ASP.NET Core.</td></tr><tr><td>CMS</td><td>Content Management System â application for creating, managing, and publishing website content, often with roles, workflows, and plugins; headless CMS expose content via APIs.</td><td>WordPress/Drupal; headless CMS like Contentful/Sanity.</td></tr><tr><td>CSR</td><td>Client-Side Rendering â render in the browser via JS.</td><td>React SPA renders views on the client.</td></tr><tr><td>CSS</td><td>Cascading Style Sheets â style language for HTML.</td><td>Tailwind/vanilla CSS styles pages.</td></tr><tr><td>DOM</td><td>Document Object Model â tree for HTML/XML.</td><td><code>document.querySelector()</code> manipulates nodes.</td></tr><tr><td>ES</td><td>ECMAScript â JavaScript specification.</td><td>ES2023 features.</td></tr><tr><td>GraphQL</td><td>Query language/runtime for typed APIs.</td><td>Client requests specific fields only.</td></tr><tr><td>HTML</td><td>HyperText Markup Language â web markup.</td><td><code><div></code>, <code><a></code>, <code><section></code> structure pages.</td></tr><tr><td>IIS</td><td>Internet Information Services â Microsoft's web server software for Windows.</td><td>Host ASP.NET applications on Windows Server with IIS.</td></tr><tr><td>JS</td><td>JavaScript â language of the web.</td><td>Frontend apps, Node.js scripts.</td></tr><tr><td>LTR</td><td>Left-To-Right â text direction where writing proceeds from left to right; default for Latin scripts.</td><td>HTML <code>dir="ltr"</code>; ensure proper bidi handling with Unicode markers where needed.</td></tr><tr><td>NPM</td><td>Node Package Manager â default package manager and registry client for Node.js, distributing JavaScript packages and managing project dependencies/scripts.</td><td><code>npm install react</code> adds dependencies; <code>package.json</code> defines scripts run via <code>npm run build</code>.</td></tr><tr><td>OpenAPI</td><td>Standard to describe HTTP APIs (Swagger).</td><td>Generate clients from <code>openapi.yaml</code>.</td></tr><tr><td>PWA</td><td>Progressive Web App â offline/installable web app.</td><td>Add service worker and manifest.</td></tr><tr><td>REST</td><td>Representational State Transfer â resource APIs.</td><td><code>GET /posts/42</code> returns a Post.</td></tr><tr><td>RTL</td><td>Right-To-Left â text direction where writing proceeds from right to left; used by scripts like Arabic and Hebrew.</td><td>HTML <code>dir="rtl"</code>; use logical CSS properties (<code>margin-inline-start</code>) for bidi layouts.</td></tr><tr><td>SEO</td><td>Search Engine Optimization â improve visibility/traffic.</td><td>Add metadata; optimize content.</td></tr><tr><td>SPA</td><td>Single Page Application â dynamic single page.</td><td>React/Vue app with client routing.</td></tr><tr><td>SSR</td><td>Server-Side Rendering â render HTML on server.</td><td>Next.js SSR pages.</td></tr><tr><td>TS</td><td>TypeScript â typed superset of JavaScript that compiles to plain JS.</td><td>Add static types/interfaces; transpile with <code>tsc</code> or bundlers.</td></tr><tr><td>UA</td><td>User Agent â identifier string a client sends describing the softw
1are, version, and sometimes device/OS.</td><td>HTTP <code>User-Agent</code> header; spoof/rotate UA for testing/scraping.</td></tr><tr><td>URI</td><td>Uniform Resource Identifier â generic identifier for names/addresses of resources; includes URLs (locators) and URNs (names).</td><td><code>mailto:[email protected]</code>, <code>urn:isbn:9780143127796</code>, <code>https://example.com/</code>.</td></tr><tr><td>URL</td><td>Uniform Resource Locator â reference (address) to resources on a network using a scheme, host, and path.</td><td><code>https://example.com/docs/index.html</code>.</td></tr><tr><td>URN</td><td>Uniform Resource Name â a URI that names a resource without specifying its location; persistent, locationâindependent identifiers.</td><td><code>urn:isbn:9780143127796</code>, <code>urn:uuid:123e4567-e89b-12d3-a456-426614174000</code>.</td></tr><tr><td>WASM</td><td>WebAssembly â portable fast binary format.</td><td>Run Rust/C++ in the browser.</td></tr><tr><td>WCAG</td><td>Web Content Accessibility Guidelines â the primary international standard for web accessibility, published by the W3C.</td><td>Aim for WCAG 2.1 AA compliance with sufficient color contrast and keyboard navigation.</td></tr><tr><td>WSGI</td><td>Web Server Gateway Interface â the standard interface between Python web applications and web servers.</td><td>Gunicorn/uWSGI running a Flask/Django app via a WSGI callable.</td></tr><tr><td>WWW</td><td>World Wide Web â system of interlinked hypertext documents and resources accessed via the internet using HTTP(S) and URLs.</td><td>Browse websites over HTTPS with a web browser.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>ASP</td><td>Active Server Pages â Microsoft's first server-side script engine for dynamically generated web pages; superseded by ASP.NET.</td><td>Classic ASP with VBScript (<code><% ... %></code>) on IIS.</td></tr><tr><td>CGI</td><td>Common Gateway Interface â standard for web servers to execute external programs and generate dynamic content.</td><td>Apache invoking a CGI script to render a page.</td></tr><tr><td>IE</td><td>Internet Explorer â Microsoft's legacy web browser, superseded by Edge.</td><td>IE11 compatibility mode; legacy intranet sites requiring ActiveX.</td></tr><tr><td>JSP</td><td>Jakarta Server Pages (JavaServer Pages) â a technology for creating dynamically generated web pages with Java code embedded in HTML.</td><td><code>.jsp</code> files compiled into servlets on a Java application server.</td></tr><tr><td>WSDL</td><td>Web Services Description Language â an XML-based interface definition language for describing the functionality of a SOAP web service.</td><td>Generate a client proxy from a <code>.wsdl</code> file; <code>?wsdl</code> endpoint on a SOAP service.</td></tr><tr><td>XHR</td><td>XMLHttpRequest â legacy browser API for making HTTP requests from JavaScript (superseded by <code>fetch</code>).</td><td><code>xhr.open('GET', '/api')</code>; handle <code>onreadystatechange</code>.</td></tr></tbody></table><h2 id="programming-languages" tabindex="-1"><a class="header-anchor" href="#programming-languages"><span>Programming Languages</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>PHP</td><td>PHP: Hypertext Preprocessor â a widely-used open source general-purpose scripting language that is especially suited for web development.</td><td>WordPress, Laravel, and Symfony are built with PHP.</td></tr><tr><td>VB.NET</td><td>Visual Basic .NET â the modern, object-oriented successor to classic VB, running on the .NET platform.</td><td>Build Windows Forms or ASP.NET applications with VB.NET.</td></tr><tr><td>VBA</td><td>Visual Basic for Applications â the scripting language for Microsoft Office, used for automation and macros.</td><td>Automate Excel reports with VBA macros in the VBE.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>APL</td><td>A Programming Language â an array-oriented language known for its concise syntax using a special character set.</td><td>Financial modeling and data manipulation with APL's vector and matrix operations.</td></tr><tr><td>AWK</td><td>Aho, Weinberger, and Kernighan â a domain-specific language for text processing, typically used for data extraction and reporting.</td><td><code>awk '{print $1}' file.txt</code> to print the first column of a file.</td></tr><tr><td>BASIC</td><td>Beginner'
1s All-purpose Symbolic Instruction Code â simple, interactive language designed for accessibility, popular on microcomputers.</td><td><code>10 PRINT "HELLO"</code>, <code>20 GOTO 10</code>; Microsoft BASIC, Dartmouth BASIC.</td></tr><tr><td>COBOL</td><td>COmmon Business-Oriented Language â verbose, English-like language for business, finance, and administrative systems on mainframes.</td><td><code>IDENTIFICATION DIVISION.</code>, <code>PERFORM ... UNTIL ...</code>; legacy financial systems.</td></tr><tr><td>FORTRAN</td><td>FORmula TRANslation â pioneering compiled language for numeric and scientific computing.</td><td><code>DO</code> loops, <code>GOTO</code>, <code>COMMON</code> blocks; used in HPC and scientific libraries.</td></tr><tr><td>LISP</td><td>LISt Processing â early, influential high-level language family based on lambda calculus, pioneering many FP concepts and featuring code-as-data (homoiconicity).</td><td><code>(defun factorial (n) ...)</code> in Common Lisp/Scheme; Emacs Lisp.</td></tr><tr><td>ML</td><td>MetaLanguage â an influential family of functional programming languages known for its static type system, type inference, and algebraic data types.</td><td>Standard ML (SML) and OCaml are popular dialects; influenced F#, Rust, and Haskell.</td></tr><tr><td>PL/I</td><td>Programming Language One â an imperative language developed by IBM for scientific, engineering, and business applications, combining features from FORTRAN and COBOL.</td><td>Legacy applications on IBM mainframes (z/OS).</td></tr><tr><td>RPG</td><td>Report Program Generator â a high-level language for business applications, primarily on IBM i (AS/400) systems.</td><td>Business logic in fixed-format RPG IV on an IBM iSeries server.</td></tr><tr><td>SML</td><td>Standard ML â a popular dialect of the ML programming language, known for its formal definition and use in language research.</td><td>SML/NJ and MLton are common compilers; used in theorem provers.</td></tr><tr><td>VB</td><td>Visual Basic (Classic) â event-driven language and IDE for rapid application development on Windows before .NET.</td><td>VB6 applications with COM components and ADO database connections.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>ALGOL</td><td>ALGOrithmic Language â influential early family of imperative languages that introduced block structure, lexical scope, and formal grammar definition (BNF).</td><td>ALGOL 60/68 influenced Pascal, C, and many other languages.</td></tr></tbody></table><h2 id="programming" tabindex="-1"><a class="header-anchor" href="#programming"><span>Programming</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AAA</td><td>ArrangeâActâAssert â unit testing pattern that structures tests into setup (arrange inputs/fixtures), execution (act), and verification (assert expected outcomes).</td><td>Arrange a service and mocks; Act by calling the method; Assert on result and interactions.</td></tr><tr><td>ADT</td><td>Abstract Data Type â specification of behavior independent of implementation.</td><td>Stack/queue ADTs with array- or list-based implementations.</td></tr><tr><td>ADT</td><td>Algebraic Data Type â composite types formed by sums (variants) and products (fields), enabling expressive, type-safe modeling.</td><td>Rust enums/Haskell data types; Option/Either in FP.</td></tr><tr><td>AIO</td><td>Asynchronous I/O â a form of I/O processing that permits other processing to continue before the transmission has finished.</td><td>Linux <code>io_uring</code> or Windows IOCP for high-performance servers.</td></tr><tr><td>API</td><td>Application Programming Interface â a defined surface for one piece of software to interact with another.</td><td>POSIX file APIs, a graphics library API, or an HTTP endpoint.</td></tr><tr><td>ASM</td><td>Assembly Language â low-level programming language with a strong correspondence between instructions and the machine's architecture.</td><td>Write <code>syscall</code> wrappers in ASM; optimize hot loops with SIMD intrinsics or inline assembly.</td></tr><tr><td>AVL</td><td>Adelson-Velsky and Landis tree â selfâbalancing binary search tree that maintains height balance via rotations to ensure O(log n) search/insert/delete.</td><td>Implement an ordered map/set with AVL rotations (LL/LR/RL/RR).</td></tr><tr><td>BAR</td><td>Base Address Register â PCI/PCIe register that stores the base address and size of a device resource so the host can map memory-mapped I/O or port ranges into the system address space.</td><td>
1GPUs/network cards expose VRAM or control registers via BARs; "Resizable BAR" allows mapping full GPU memory on modern systems.</td></tr><tr><td>BCL</td><td>Base Class Library â the standard library of core types and functions in the .NET Framework and its successors.</td><td>Use types from <code>System</code> namespace like <code>String</code>, <code>List<T></code>, and <code>HttpClient</code>.</td></tr><tr><td>BEAM</td><td>Bogdan's Erlang Abstract Machine â the virtual machine at the core of the Erlang and Elixir ecosystems, known for its concurrency and fault tolerance.</td><td>The BEAM VM powers highly concurrent systems like WhatsApp.</td></tr><tr><td>BFS</td><td>Breadth-First Search â graph/tree traversal that visits neighbors level by level using a queue; finds shortest paths in unweighted graphs.</td><td>Level-order traversal of a tree; BFS from a source to compute distances/parents.</td></tr><tr><td>BSP</td><td>Binary Space Partitioning â recursively subdivide space with hyperplanes (planes in 3D, lines in 2D) to organize geometry for visibility, rendering order, and collision queries.</td><td>Classic FPS engines (e.g., Quake) use BSP trees for visibility/culling and painter's algorithm ordering.</td></tr><tr><td>BST</td><td>Binary Search Tree â ordered binary tree supporting average O(log n) search/insert/delete when balanced; worstâcase O(n) if unbalanced.</td><td>Implement sets/maps; inorder traversal yields keys in sorted order.</td></tr><tr><td>CAS</td><td>Compare-And-Swap â atomic operation that updates a memory location only if it still equals an expected value; foundation for lockâfree algorithms.</td><td>CAS loop for a lockâfree stack push; beware the ABA problem.</td></tr><tr><td>CLI</td><td>Command-Line Interface â text-based commands.</td><td><code>git</code>, <code>kubectl</code>, custom CLIs.</td></tr><tr><td>CLI</td><td>Common Language Infrastructure â the open specification (ECMA-335) for the .NET runtime environment.</td><td>The .NET CLR is an implementation of the CLI standard.</td></tr><tr><td>CLR</td><td>Common Language Runtime â .NET VM.</td><td>Runs C# assemblies.</td></tr><tr><td>CRUD</td><td>Create, Read, Update, Delete â basic data ops.</td><td>REST endpoints map to CRUD on <code>users</code>.</td></tr><tr><td>CUI</td><td>Character User Interface â text/character-based UI typically rendered in terminals with limited graphics; overlaps with TUI.</td><td>Installer wizards and ncurses-style menus in a terminal.</td></tr><tr><td>DAG</td><td>Directed Acyclic Graph â directed graph with no cycles; commonly used to model dependencies and enable topological ordering in compilers, build systems, and task scheduling.</td><td>Topologically sort to order compilation units; represent dependencies in build graphs or AST passes.</td></tr><tr><td>DFS</td><td>Depth-First Search â graph/tree traversal that explores as far as possible along each branch before backtracking; typically implemented with recursion or an explicit stack.</td><td>Topological sort, cycle detection, connected components, subtree times.</td></tr><tr><td>DSL</td><td>Domain-Specific Language â tailored language.</td><td>SQL, Regex, build DSLs.</td></tr><tr><td>EOF</td><td>End Of File â no more data to read.</td><td>Read returns EOF on file end.</td></tr><tr><td>FASM/MASM/NASM/TASM</td><td>Flat Assembler / Microsoft Macro Assembler / Netwide Assembler / Turbo Assembler â popular assemblers for the x86 architecture.</td><td>Writing bootloaders or optimizing code with x86 assembly.</td></tr><tr><td>FFI</td><td>Foreign Function Interface â mechanism to call functions across language/ABI boundaries.</td><td>Rust <code>extern "C"</code> to call C; Python <code>ctypes</code>/<code>cffi</code> bindings.</td></tr><tr><td>FIFO</td><td>First In, First Out â queue discipline.</td><td>Message queues processing order.</td></tr><tr><td>FP</td><td>Functional Programming â pure functions/immutability.</td><td>Map/filter/reduce pipelines.</td></tr><tr><td>FSM</td><td>Finite State Machine â computational model with a finite number of states and transitions driven by input
1s/events.</td><td>UI workflows, protocol handlers, and parsers modeled as FSMs.</td></tr><tr><td>GADT</td><td>Generalized Algebraic Data Type â ADT whose constructors can refine the result type, enabling more precise typing and safer pattern matches.</td><td>Haskell/OCaml GADTs for typed ASTs; matching narrows types.</td></tr><tr><td>GC</td><td>Garbage Collection â automatic memory management.</td><td>JVM/CLR collectors free unused objects.</td></tr><tr><td>gRPC</td><td>High-performance RPC over HTTP/2 with Protobuf.</td><td>Define <code>.proto</code>; generate client/server stubs.</td></tr><tr><td>GUI</td><td>Graphical User Interface â visual interaction.</td><td>Desktop app windows, buttons.</td></tr><tr><td>I/O</td><td>Input/Output â transfer of data to/from a program and external systems or devices.</td><td>File I/O, network I/O; blocking vs nonâblocking/async I/O.</td></tr><tr><td>IDE</td><td>Integrated Development Environment â all-in-one dev app.</td><td>IntelliJ, VS Code (w/ extensions).</td></tr><tr><td>IDL</td><td>Interface Definition Language â specification language to describe interfaces and data types for generating cross-language bindings and IPC stubs.</td><td>Define COM interfaces in MIDL or CORBA IDL; generate proxies/stubs for RPC.</td></tr><tr><td>IIFE</td><td>Immediately Invoked Function Expression.</td><td><code>(function(){ })()</code> in JS.</td></tr><tr><td>JDBC</td><td>Java Database Connectivity â DB API.</td><td><code>DriverManager.getConnection(...)</code>.</td></tr><tr><td>JDK</td><td>Java Development Kit â Java dev tools.</td><td><code>javac</code>, <code>jar</code>.</td></tr><tr><td>JRE</td><td>Java Runtime Environment â run Java apps.</td><td><code>java -jar app.jar</code>.</td></tr><tr><td>JVM</td><td>Java Virtual Machine â runs bytecode.</td><td>JVM-based languages (Kotlin, Scala).</td></tr><tr><td>LINQ</td><td>Language-Integrated Query â a .NET feature that adds native data querying capabilities to languages like C#.</td><td>Use LINQ to query collections, databases (via EF), and XML.</td></tr><tr><td>LRU</td><td>Least Recently Used â cache eviction policy that discards the least recently accessed items first.</td><td>LRU caches/maps in memory-constrained systems.</td></tr><tr><td>LSB</td><td>Least Significant Bit â the bit with the lowest positional value in a binary number (2^0); determines odd/even and is affected first by increment.</td><td>In 0b1011, the LSB is 1; littleâendian stores LSB byte first.</td></tr><tr><td>LSP</td><td>Language Server Protocol â standard JSON-RPC protocol between editors and language servers for code intelligence.</td><td>VS Code/Neovim language servers for hover, completion, diagnostics.</td></tr><tr><td>MSB</td><td>Most Significant Bit â the bit with the highest positional value; often used as the sign bit in signed integers.</td><td>In 0b1011, the MSB is 1; bigâendian stores MSB byte first.</td></tr><tr><td>MST</td><td>Minimum Spanning Tree â subset of edges that connects all vertices in a weighted, undirected graph with minimum total weight and no cycles.</td><td>Compute MST with Kruskal (sort edges + DSU) or Prim (priority queue).</td></tr><tr><td>NaN</td><td>Not a Number â IEEE 754 floatingâpoint special value representing undefined/invalid results; propagates through computations and is unordered (not equal to any value, including itself).</td><td><code>0.0/0.0</code> or <code>sqrt(-1.0)</code> produce NaN; <code>NaN != NaN</code> is true; use <code>isnan()</code> to test.</td></tr><tr><td>NOP</td><td>No Operation â instruction or operation that intentionally does nothing; used for timing, alignment, patching, or as a placeholder.</td><td>CPU <code>NOP</code> instruction; inserting a noâop in pipelines or bytecode.</td></tr><tr><td>NPE</td><td>Null Pointer Exception â runtime error arising from dereferencing a null reference/pointer in languages with nullable references.</td><td>Java <code>NullPointerException</code>, C# <code>NullReferenceException</code>; avoid with null checks, Option/Optional, or nullâsafety features.</td></tr><tr><td>ODBC</td><td>
1Open Database Connectivity â cross-platform C API and driver model for accessing relational databases.</td><td>Configure DSNs; apps connect via ODBC drivers to SQL Server/MySQL/Postgres.</td></tr><tr><td>OLE</td><td>Object Linking and Embedding â Microsoft technology (built on COM) for embedding and linking documents/objects between applications.</td><td>Embed an Excel sheet in a Word doc; OLE automation for Office apps.</td></tr><tr><td>OOM</td><td>Out Of Memory â condition where available memory is exhausted and allocations fail.</td><td>Linux OOM killer terminates processes; runtime throws OOM error.</td></tr><tr><td>OOP</td><td>Object-Oriented Programming â encapsulation/inheritance/polymorphism.</td><td>Classes, interfaces, virtual methods.</td></tr><tr><td>ORM</td><td>Object-Relational Mapping â map objects to relational tables.</td><td>ORM entities and repositories.</td></tr><tr><td>OTP</td><td>Open Telecom Platform â the standard library, design principles, and set of tools for building robust, concurrent systems in Erlang/Elixir.</td><td><code>gen_server</code> and <code>supervisor</code> are key OTP behaviours.</td></tr><tr><td>PCRE</td><td>Perl Compatible Regular Expressions â regex libraries and syntax compatible with Perl's regex engine (PCRE/PCRE2).</td><td><code>grep -P</code>, nginx, PHP use PCRE/PCRE2 for advanced regex features.</td></tr><tr><td>RAII</td><td>Resource Acquisition Is Initialization â lifetime control.</td><td>C++ locks released at scope end.</td></tr><tr><td>Regex</td><td>Regular Expression â declarative pattern syntax for matching, searching, and transforming strings; available in most languages and tooling with varying feature levels (POSIX, PCRE, etc.).</td><td>Use <code>/^foo.*bar$/</code> to validate inputs; run `rg --ignore-case 'error</td></tr><tr><td>REPL</td><td>ReadâEvalâPrint Loop â interactive shell.</td><td>Python/Node REPL.</td></tr><tr><td>RPC</td><td>Remote Procedure Call â call functions on a service.</td><td>gRPC <code>CreateUser</code> method.</td></tr><tr><td>RPN</td><td>Reverse Polish Notation â postfix notation for arithmetic expressions that eliminates parentheses and associates operators with operands directly; naturally evaluated with a stack.</td><td>Evaluate <code>3 4 + 2 *</code> with a stack; HP calculators and some compilers/VMs use RPN internally.</td></tr><tr><td>SDK</td><td>Software Development Kit â tools/libs for a platform.</td><td>AWS SDK for programmatic access.</td></tr><tr><td>SICP</td><td>Structure and Interpretation of Computer Programs â seminal MIT textbook that teaches computer science fundamentals through Scheme, abstraction, and metalinguistic evaluation.</td><td>Work through the SICP exercises, building interpreters and analyzers to internalize recursion, higher-order procedures, and data-driven design.</td></tr><tr><td>SUT</td><td>System Under Test â the specific component or boundary being exercised by a test, often isolated from collaborators via test doubles.</td><td>Unit test drives the SUT (a service class) while stubbing its repository and asserting outputs/interactions.</td></tr><tr><td>TLS</td><td>Thread-Local Storage â per-thread storage for data that gives each thread its own instance of a variable.</td><td>C/C++ <code>thread_local</code>/<code>__thread</code>, POSIX <code>pthread_key_create</code>; Rust <code>thread_local!</code>.</td></tr><tr><td>TUI</td><td>Text-based User Interface â terminal UI.</td><td><code>htop</code>, <code>ncurses</code> apps.</td></tr><tr><td>UB</td><td>Undefined Behaviour â program operations for which the language standard imposes no requirements, allowing compilers to assume they never happen and enabling aggressive optimizations.</td><td>C/C++ outâofâbounds access, useâafterâfree, signed overflow; can lead to unpredictable results; use sanitizers to detect.</td></tr><tr><td>UTC</td><td>Coordinated Universal Time â global time standard.</td><td>Timestamps/logs in UTC.</td></tr><tr><td>UWP</td><td>Universal Windows Platform â a platform for creating apps that run across Windows devices.</td><td>Build a Windows Store app with UWP and XAML.</td></tr><tr><td>VBE</td><td>Visual Basic Editor â the integrated development environment for writing and editing VBA code within Microsoft Office.</td><td>Press Alt+F11 in Excel to open the VBE.</td></tr><tr><td>VS</td><td>Visual Studio â Microsoft's integrated development environment (IDE) for .NET and C++ development on Windows.</td><td>Develop, debug, and deploy applications with the Visual Studio IDE.</td></tr><tr><td>WPF</td><td>Windows Presentation Foundation â a UI framework for building Windows desktop applications with XAML.</td><td>Modern desktop apps with data binding and hardware acceleration.</td></tr><tr><td>WYSIWYG</td><td>What You See Is What You Get â direct-manipulation editor.</td><td>Rich text editors.</td></tr><tr><td>XAML</td><td>Extensible Application Markup Language â a declarative markup language used by Microsoft UI frameworks like WPF and UWP.</td><td>Define UI layouts and data bindings in <code>.xaml</code> files.</td></tr><tr><td><strong>Historical</strong> {colspan=-3}</td><td></td><td></td></tr><tr><td>RMI</td><td>Remote Method Invocation â Java's distributed objects technology enabling method calls on remote JVMs via stubs/skeletons over JRMP (or IIOP for RMIâIIOP).<
1/td><td>Early Java distributed systems; largely supplanted by HTTP/REST, gRPC, and message queues.</td></tr></tbody></table><h2 id="compilers" tabindex="-1"><a class="header-anchor" href="#compilers"><span>Compilers</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>ANTLR</td><td>ANother Tool for Language Recognition â a popular parser generator for reading, processing, executing, or translating structured text or binary files.</td><td>Generate a parser from a grammar file for a custom language.</td></tr><tr><td>AOT</td><td>Ahead-Of-Time compilation â compile before runtime.</td><td>Angular AOT compiles templates during build.</td></tr><tr><td>AST</td><td>Abstract Syntax Tree â structured tree representation of parsed source code used by compilers and tooling.</td><td>AST nodes for statements/expressions in parsers/linters.</td></tr><tr><td>BNF</td><td>BackusâNaur Form â notation for expressing contextâfree grammars used to define programming language syntax.</td><td>Language specs define grammar productions in BNF or EBNF.</td></tr><tr><td>CFG</td><td>ContextâFree Grammar â formal grammar class used to define programming language syntax; typically expressed in BNF/EBNF and parsed by LL/LR/GLR/PEG parsers.</td><td>Write grammar productions; generate parsers with yacc/bison/ANTLR.</td></tr><tr><td>CFG</td><td>Control Flow Graph â directed graph of basic blocks and edges representing possible control transfers within a function/program; foundation for dataâflow analysis and many optimizations.</td><td>Build CFG to compute dominators/loops; enable DCE, SSA construction, and liveness.</td></tr><tr><td>CIL</td><td>Common Intermediate Language â the bytecode language for the .NET runtime (CLR), to which languages like C# and VB.NET compile.</td><td><code>ildasm</code> to inspect the CIL of a .NET assembly; also known as MSIL.</td></tr><tr><td>CSE</td><td>Common Subexpression Elimination â remove repeated identical expressions by computing once and reusing the value within a region.</td><td>Within a block, compute <code>x+y</code> once and reuse; global variants extend across blocks.</td></tr><tr><td>DCE</td><td>Dead Code Elimination â remove code shown by analysis to have no effect on program outputs/side effects, improving size and performance.</td><td>Eliminate unused assignments/branches after liveness/constant propagation; <code>-O2</code> passes in LLVM/GCC.</td></tr><tr><td>DFA</td><td>Data Flow Analysis â family of static analyses that compute facts about program variables/paths over a control flow graph using lattice/transfer functions (e.g., reaching definitions, liveness, constant propagation).</td><td>Run forward/backward analyses on a CFG; feed results to optimizations like DCE, CSE, and register allocation.</td></tr><tr><td>DFA</td><td>Deterministic Finite Automaton â finite-state machine with exactly one transition per symbol for each state; used in lexers/pattern matching.</td><td>Tokenizer state machine generated from regular languages.</td></tr><tr><td>DWARF</td><td>Debug With Arbitrary Record Format â standardized debugging information format for compiled programs (types, symbols, line tables, call frames) used across platforms.</td><td>GCC/Clang emit DWARF in ELF/Mach-O; inspect with <code>readelf --debug-dump</code> or <code>llvm-dwarfdump</code>; GDB/LLDB consume DWARF.</td></tr><tr><td>EBNF</td><td>Extended BackusâNaur Form â BNF with additional operators (repetition, optional, grouping) for more concise grammar specifications.</td><td><code>{ }</code> repetition, <code>[ ]</code> optional; used in many language grammars and docs.</td></tr><tr><td>FAM</td><td>Flexible Array Member â language/ABI feature where a structâs last field is a sizeâunspecified array used to tailâallocate variableâlength data; not counted in <code>sizeof</code> and requires custom allocation/copy logic.</td><td>In C (C99+): <code>struct S{size_t n; int a[];};</code> allocate with <code>malloc(sizeof(struct S)+n*sizeof(int))</code>; <code>a</code> occupies trailing storage.</td></tr><tr><td>GCC</td><td>GNU Compiler Collection â suite of compilers for C/C++/Fortran and more.</td><td><code>gcc</code>/<code>g++</code> toolchains for building software.</td></tr><tr><td>GL</td><td>Graphics Library â SGI's proprietary immediate-mode 3D graphics API for IRIS workstations; precursor to the portable OpenGL standard.</td><td>Develop IRIS GL applications on SGI hardware; OpenGL later standardized much of the API for cross-platform use.</td></tr><tr><td>GLSL</td><td>
1OpenGL Shading Language â high-level C-like language for writing programmable shaders targeting OpenGL and Vulkan (via SPIR-V).</td><td>Write vertex/fragment/compute shaders compiled by drivers or offline to SPIR-V for Vulkan pipelines.</td></tr><tr><td>GVN</td><td>Global Value Numbering â discover semantically equivalent computations (beyond syntactic equality) to eliminate redundancies across the dominator tree.</td><td>Treat <code>t=x; z=t+y</code> as <code>x+y</code>; coalesce values through copies/Ï nodes in SSA.</td></tr><tr><td>HLSL</td><td>High-Level Shading Language â Microsoftâs shader language for DirectX that compiles to DXIL/DXBC and can be cross-compiled to SPIR-V for Vulkan.</td><td>Author shaders in HLSL for Direct3D 11/12; use DXC/FXC or SPIRV-Cross for other runtimes.</td></tr><tr><td>HM</td><td>HindleyâMilner â a classical type inference algorithm that automatically deduces the types of expressions in some statically typed languages.</td><td>The basis for type inference in ML-family languages and Haskell.</td></tr><tr><td>IR</td><td>Intermediate Representation â compiler/transformation-friendly program form between source and machine code.</td><td>LLVM IR, SSA-based IRs used for optimization.</td></tr><tr><td>JIT</td><td>Just-In-Time compilation â runtime optimization.</td><td>HotSpot JIT compiles hot methods.</td></tr><tr><td>LICM</td><td>Loop-Invariant Code Motion â hoist computations whose operands donât change within a loop to preheaders, and sink postâloop where safe.</td><td>Move <code>len(arr)</code>/<code>c*2</code> out of the loop body to reduce work.</td></tr><tr><td>LLVM</td><td>Low Level Virtual Machine â modular compiler toolchain and IR used by many languages.</td><td>Clang/LLVM backends, <code>llc</code>, <code>opt</code>, and LLVM IR.</td></tr><tr><td>LTO</td><td>Link Time Optimization â wholeâprogram optimization performed at link time across translation units, typically by linking IR/bitcode and running interprocedural passes.</td><td><code>-flto</code> in Clang/GCC; enables crossâTU inlining, DCE, devirtualization, ICF/WPO.</td></tr><tr><td>MLIR</td><td>Multi-Level Intermediate Representation â an extensible compiler infrastructure in LLVM that models programs across dialects to enable reusable transformations for domain-specific compilers and accelerators.</td><td>Use MLIR dialects (Linalg, GPU, Tensor) to lower ML programs toward LLVM IR or hardware-specific codegen.</td></tr><tr><td>NFA</td><td>Nondeterministic Finite Automaton â automaton model for regular languages allowing εâtransitions and multiple possible next states; typically converted to an equivalent DFA for efficient matching.</td><td>Build NFA from regex via Thompson's construction; convert to DFA by subset construction for lexers.</td></tr><tr><td>NRVO</td><td>Named Return Value Optimization â compiler optimization that elides copies/moves by constructing a named local return object directly in the callerâs storage.</td><td><code>T f(){ T x; return x; }</code> constructs <code>x</code> in the caller (C++); differs from RVO on unnamed temporaries.</td></tr><tr><td>OBJ</td><td>Object File â intermediate binary produced by compilers/assemblers containing machine code, data, relocation records, and symbol tables to be linked into executables or libraries.</td><td>Build <code>foo.o</code>/<code>foo.obj</code> then link with <code>ld</code>/<code>link.exe</code>; inspect with <code>objdump</code>, <code>otool</code>, or <code>llvm-objdump</code>.</td></tr><tr><td>PEG</td><td>Parsing Expression Grammar â recognitionâbased grammar formalism with ordered (prioritized) choice and unlimited lookahead; often parsed via packrat parsing with memoization for linear time.</td><td>Define a PEG for a language and parse with PEG.js/pest/PEGTL; use ordered choice instead of ambiguous CFGs.</td></tr><tr><td>PRE</td><td>Partial Redundancy Elimination â inserts computations to make partially redundant expressions fully redundant, then removes duplicates (often via Lazy Code Motion/SSA-PRE).</td><td>If <code>a+b</code> happens on some paths and later unconditionally, place it optimally so all uses share one computed value.</td></tr><tr><td>RTTI</td><td>Run-Time Type Information â runtime facility to query an object's dynamic type and perform safe downcasts/instance checks in languages with polymorphism.</td><td>In C++, use <code>dynamic_cast<Base*></code> and <code>typeid</code>; in Java/C#, use <code>instanceof</code>/<code>is</code> and reflection APIs.</td></tr><tr><td>RVO</td><td>Return Value Optimization â compiler optimization that elides copies/moves by constructing a returned temporary directly in the callerâs storage.</td><td><code>T f(){ return T(); }</code> constructs the <code>T</code> in the caller; guaranteed in C++17 (copy elision rules).</td></tr><tr><td>SPIR-V</td><td>Standard Portable Intermediate Representation â Khronos binary intermediate language for GPU compute/graphics shaders used by Vulkan, OpenCL, and WebGPU toolchains.</td><td>Compile GLSL/HLSL to SPIR-V for Vulkan pipelines; emit SPIR-V from MLIR/LLVM for compute shaders.</td></tr><tr><td>SSA</td><td>Static Single Assignment â IR form where each variable is assigned exactly once, using Ï (phi) functions at merge points; simplifies dataâflow analysis and optimization.</td><td>Convert to SSA to enable efficient DCE, copy propagation, and value numbering; SSA in LLVM IR.</td></tr><tr><td>TCO</td><td>Tail Call Optimization â reuse the current stack frame for a tail call to avoid stack growth and enable efficient tail recursion.</td><td>Compilers transform tail-recursive functions into loops; mandated in some languages (Scheme), optional in others.</td></tr><tr><td>UFCS</td><td>Uniform Function Call Syntax â language feature that allows calling free/extension functions with method-call syntax by implicitly passing the receiver as the first argument.</td><td>D/Scala/Rust desugar <code>x.f(y)</code> to <code>f(x, y)</code>; extension methods in C#/Kotlin/Swift.</td></tr></tbody></table><h2 id="operating-systems" tabindex="-1"><a class="header-anchor" href="#operating-systems"><span>Operating Systems</span></a></h2><table><thead><tr><th>
1Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>ABI</td><td>Application Binary Interface â low-level contract governing calling conventions, data layout, and linkage between compiled code and the OS/runtime.</td><td>x86â64 System V ABI, Windows x64 ABI; stable FFI boundaries.</td></tr><tr><td>APK</td><td>Android Package Kit â archived bundle (ZIP with <code>AndroidManifest.xml</code>, resources, and compiled bytecode) used to distribute and install Android apps.</td><td>Build <code>app-release.apk</code>, sign it, and install with <code>adb install</code> or upload to Play.</td></tr><tr><td>ASLR</td><td>Address Space Layout Randomization â security technique that randomizes process address spaces (stack/heap/ASLR-enabled libs) to make memory corruption exploits less reliable.</td><td><code>cat /proc/sys/kernel/randomize_va_space</code>; Windows system-wide ASLR.</td></tr><tr><td>BAT</td><td>Batch file â Windows Command Prompt script file executed by <code>cmd.exe</code>; commonly <code>.bat</code> or <code>.cmd</code>.</td><td>Automation scripts using built-ins like <code>echo</code>, <code>set</code>, <code>if</code>, <code>for</code>.</td></tr><tr><td>BSD</td><td>Berkeley Software Distribution â family of UNIX-like operating systems descended from research UNIX at UC Berkeley, known for its permissive license.</td><td>FreeBSD, OpenBSD, NetBSD used in servers and embedded systems.</td></tr><tr><td>BSS</td><td>Block Started by Symbol â segment for zeroâinitialized or uninitialized static/global data that occupies memory at load/runtime but takes no space in the object file beyond metadata (size).</td><td>C <code>static int buf[4096];</code> goes to <code>.bss</code>; reduces binary size versus storing zeros.</td></tr><tr><td>CMD</td><td>Windows Command Prompt â command-line interpreter (<code>cmd.exe</code>) for Windows providing batch scripting (.bat/.cmd) and built-in shell commands.</td><td>Run <code>cmd.exe</code>; use <code>dir</code>, <code>copy</code>, <code>set</code> and <code>%PATH%</code>; legacy scripts for automation.</td></tr><tr><td>COW</td><td>Copy-On-Write â share pages or objects until a write occurs, then copy to preserve isolation;
1 reduces memory/IO and enables efficient forks/snapshots.</td><td><code>fork()</code> shares pages COW; VM snapshots; filesystem COW in ZFS/Btrfs.</td></tr><tr><td>DLL</td><td>Dynamic-Link Library â shared library format on Windows loaded at runtime into a process address space.</td><td><code>foo.dll</code> loaded via LoadLibrary; shared code/plugins.</td></tr><tr><td>DPC</td><td>Deferred Procedure Call â mechanism (notably in Windows) to queue a function for execution at a lower IRQL than the ISR that scheduled it, enabling faster interrupt handling.</td><td>A network driver's ISR queues a DPC to process incoming packets.</td></tr><tr><td>DSO</td><td>Dynamic Shared Object â generic term for a shared library (<code>.so</code>, <code>.dll</code>, <code>.dylib</code>) loaded at runtime and linked into a process's address space.</td><td>Use <code>dlopen</code> to load a DSO and <code>dlsym</code> to resolve symbols from it.</td></tr><tr><td>DYLIB</td><td>Dynamic Library â macOS shared library format loaded by the dynamic linker.</td><td><code>libfoo.dylib</code> via dyld; <code>install_name_tool</code>/rpaths for relocation.</td></tr><tr><td>ELF</td><td>Executable and Linkable Format â standard binary format for executables, object files, and shared libraries on Unix-like systems.</td><td>Linux binaries with sections/segments; inspect with <code>readelf</code>/<code>objdump</code>.</td></tr><tr><td>EXE</td><td>Executable file â Windows program file using the Portable Executable (PE) format for executables and DLLs.</td><td>Launch <code>.exe</code> apps; inspect PE headers with <code>dumpbin</code>/<code>objdump</code>.</td></tr><tr><td>FS</td><td>File System â on-disk or logical structure and set of rules the OS uses to organize, store, and retrieve files/directories, including metadata and allocation.</td><td>ext4, NTFS, APFS, ZFS; mount/unmount volumes; permissions and journaling.</td></tr><tr><td>FUSE</td><td>Filesystem in Userspace â kernel interface to implement filesystems in user space processes.</td><td>Mount <code>sshfs</code>/<code>rclone</code> via FUSE; custom FS without kernel modules.</td></tr><tr><td>GDT</td><td>Global Descriptor Table â a core data structure in the x86 architecture that defines memory segments for the CPU.</td><td>Kernel setup of GDT for code/data segments in protected mode.</td></tr><tr><td>GNOME</td><td>GNU Network Object Model Environment â free, openâsource desktop environment for UNIX-like systems, part of the GNU Project.</td><td>Default desktop on many Linux distributions; GNOME Shell with Wayland/X11.</td></tr><tr><td>HAL</td><td>Hardware Abstraction Layer â OS layer that hides hardware specifics behind a uniform API so drivers/system code can run across platforms.</td><td>Windows HAL; OS kernels providing common driver interfaces across architectures.</td></tr><tr><td>IDT</td><td>Interrupt Descriptor Table â x86 data structure that associates interrupt vectors with the addresses of their interrupt service routines (ISRs).</td><td>OS populates the IDT to handle hardware interrupts and exceptions.</td></tr><tr><td>IFS</td><td>Installable File System â an API in an operating system that allows new file systems to be loaded dynamically.</td><td>Windows IFS for NTFS, FAT32, and third-party file systems; OS/2's IFS.</td></tr><tr><td>IPC</td><td>Inter-Process Communication â exchange/coordinate between processes.</td><td>Pipes, sockets, shared memory, signals.</td></tr><tr><td>ISR</td><td>Interrupt Service Routine â function invoked by the OS in response to an interrupt to handle the event and acknowledge the controller.</td><td>Keyboard ISR on IRQ1 reads scancode; timer ISR updates ticks and EOIs the APIC.</td></tr><tr><td>KDE</td><td>K Desktop Environment (now the KDE community and Plasma desktop) â free, openâsource desktop environment and software suite for UNIX-like systems.</td><td>KDE Plasma on Linux/BSD; highly configurable desktop with KWin and Qt apps.</td></tr><tr><td>L4</td><td>L4 microkernel family â influential second-generation microkernel design emphasizing minimality, high performance, and user-space servers.</td><td>seL4 (verified secure); Fiasco.OC; used in secure embedded systems and virtualization.</td></tr><tr><td>Mach-O</td><td>Mach Object â executable/object file format used by macOS/iOS for binaries and libraries.</td><td>Inspect with <code>otool</code>/<code>lldb</code>; <code>libfoo.dylib</code> and <code>foo.app/Contents/MacOS/foo</code>.</td></tr><tr><td>MSI</td><td>Microsoft Installer â an installer package file format and API for Windows.</td><td><code>.msi</code> packages for installing software on Windows.</td></tr><tr><td>
1NDIS</td><td>Network Driver Interface Specification â a Microsoft API for network card drivers, forming a layer between the protocol stack and the hardware driver.</td><td>Writing an NDIS miniport driver; the standard for Windows network drivers.</td></tr><tr><td>NTFS</td><td>New Technology File System â Windows journaling filesystem with ACLs, alternate data streams, compression, and quotas.</td><td>Format a Windows system volume as NTFS; set ACLs with icacls.</td></tr><tr><td>OS</td><td>Operating System â system software that manages hardware resources and provides common services for programs.</td><td>Linux, Windows, macOS; kernel, drivers, processes, filesystems.</td></tr><tr><td>PCB</td><td>Process Control Block â kernel data structure containing the state of a process (registers, PID, scheduling info, memory maps).</td><td>The OS saves/restores the PCB during a context switch.</td></tr><tr><td>PE</td><td>Portable Executable â Windows binary format for executables, DLLs, and object files.</td><td>Inspect with <code>dumpbin</code>/<code>objdump</code>; sections, import/export tables.</td></tr><tr><td>PID</td><td>Process Identifier â numeric ID assigned by the kernel to a process.</td><td><code>pid=1</code> init/systemd; <code>ps -o pid,comm</code>.</td></tr><tr><td>POSIX</td><td>Portable OS Interface â Unix-like standard APIs.</td><td><code>fork</code>, <code>exec</code>, <code>pthread</code> APIs.</td></tr><tr><td>PTY</td><td>Pseudo Terminal â virtual terminal pair (master/slave) used by terminal emulators and remote sessions to emulate a real TTY.</td><td><code>/dev/pts/*</code>, <code>ssh -t</code>, <code>forkpty</code>, <code>tmux</code>.</td></tr><tr><td>QNX</td><td>
1QNX Neutrino RTOS â commercial Unix-like real-time operating system with a microkernel architecture, widely used in embedded systems.</td><td>Automotive infotainment (BlackBerry IVY), industrial controllers, medical devices.</td></tr><tr><td>RCU</td><td>Read-Copy-Update â synchronization mechanism allowing lock-free reads by deferring updates/reclamation until all readers in a grace period complete.</td><td>Linux kernel uses RCU for highly concurrent data structures in networking/VFS.</td></tr><tr><td>RPM</td><td>RPM Package Manager (originally Red Hat Package Manager) â a package management system used by many Linux distributions.</td><td><code>rpm -i package.rpm</code>; <code>yum</code>/<code>dnf</code> use RPM packages.</td></tr><tr><td>RTOS</td><td>Real-Time Operating System â OS designed for deterministic response and bounded latency, with priority-based scheduling and real-time primitives.</td><td>FreeRTOS, Zephyr, VxWorks on microcontrollers/embedded systems; hard vs soft real-time.</td></tr><tr><td>SO</td><td>Shared Object â Unix/Linux shared library format loaded by the dynamic linker.</td><td><code>libfoo.so</code> via ld.so/<code>dlopen</code>; sonames and rpaths.</td></tr><tr><td>SUS</td><td>Single UNIX Specification â standard defining UNIX interfaces and behavior maintained by The Open Group, ensuring POSIX compliance and application portability.</td><td>SUS/POSIX APIs (<code>unistd.h</code>, signals, threads); conformant systems like AIX, HP-UX, macOS.</td></tr><tr><td>TCB</td><td>Thread Control Block â kernel data structure that stores the state of a thread, including its registers, stack pointer, and scheduling information.</td><td>Analogous to a PCB but for a thread; managed by the scheduler.</td></tr><tr><td>TID</td><td>Thread Identifier â numeric ID for a thread (often equals PID for single-threaded processes; Linux has per-thread TIDs).</td><td><code>gettid()</code> on Linux; <code>pthread_self()</code> maps to a TID.</td></tr><tr><td>TPF</td><td>Transaction Processing Facility â IBM's high-performance successor to ACP, optimized for nonstop, large-scale transaction processing on mainframes in aviation, finance, and hospitality.</td><td>Airlines, card networks, and hotels run IBM ZTPF/TPF on IBM Z to process reservations and payments at extreme throughput.</td></tr><tr><td>TTY</td><td>Teletype/Terminal â character device for text I/O; terminal sessions.</td><td><code>/dev/tty</code>, PTY in shells.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>AIX</td><td>IBM's UNIX (Advanced Interactive eXecutive) for POWER systems, featuring LPARs, SMIT, JFS2, and enterprise tooling.</td><td>IBM Power Systems running AIX on POWER9/POWER10; manage with SMIT/VIOS.</td></tr><tr><td>COM</td><td>DOS executable â simple flat binary loaded at offset 0x100 with ~64KB segment limit and no header.</td><td>Classic <code>.COM</code> utilities/programs on MSâDOS/PCâDOS; tiny loaders/stubs.</td></tr><tr><td>IVT</td><td>Interrupt Vector Table â x86 realâmode table at 0x0000:0000 with 256 interrupt pointers; superseded by IDT in protected/long mode.</td><td>Bootloaders may patch IVT entries before switching modes.</td></tr><tr><td>JCL</td><td>Job Control Language â scripting language used on IBM mainframes to control batch job execution.</td><td><code>//SYSIN DD *</code> statements in a JCL deck to submit a batch job.</td></tr><tr><td>MCP</td><td>Master Control Program â Unisys mainframe OS in the Burroughs largeâsystems line, featuring a stack machine architecture and strong language support; still in use but niche.</td><td>Unisys ClearPath MCP systems (Burroughs B5000 lineage) running enterprise workloads.</td></tr><tr><td>NT</td><td>New Technology â Microsoftâs NT family/architecture underlying Windows NT and its successors (2000/XP/Vista/7/8/10/11), featuring a hybrid kernel, HAL, NTFS, and Win32/NT native subsystems.</td><td>Windows NT lineage; <code>ver</code> shows NT versioning; services/session model and security based on NT architecture.</td></tr><tr><td>UAC</td><td>User Account Control â Windows elevation and consent mechanism to limit silent privilege escalation.</td><td>Admin tasks prompt for consent; splitâtoken admin accounts.</td></tr><tr><td>UDS</td><td>Unix Domain Socket â IPC mechanism using socket endpoints on the local host with filesystem pathnames or abstract namespace.</td><td><code>/var/run/docker.sock</code>; faster than TCP on localhost.</td></tr><tr><td>VDSO</td><td>virtual Dynamic Shared Object â small shared library exposed by the kernel and mapped into user processes to provide fast, syscall-free access to certain kernel routines.</td><td><code>gettimeofday()</code> calls on Linux are often implemented via the vDSO to avoid context switches.</td></tr><tr><td>VFAT</td><td>Virtual FAT â an extension to the FAT filesystem that introduced long filename support in Windows 95.</td><td>Enabled filenames longer than the 8.3 DOS convention.</td></tr><tr><td>VFS</td><td>Virtual File System â OS abstraction layer that provides a uniform API over different filesystems and devices.</td><td>Linux VFS layer exposes common inode/dentry APIs across ext4, XFS, NFS, FUSE.</td></tr><tr><td>VM</td><td>Virtual Memory â OS abstraction that gives processes isolated address spaces mapped to physical memory via paging/segmentation.</td><td>Perâprocess address spaces, page tables, demand paging, copyâonâwrite.</td></tr><tr><td>X11</td><td>X Window System (Version 11) â networkâtransparent windowing system and protocol for bitmap displays on UNIXâlike systems.</td><td>Xorg/XWayland on Linux; XQuartz on macOS; <code>ssh -X</code> X11 forwarding.</td></tr><tr><td>z/OS</td><td>IBM's mainframe operating system for IBM Z, successor to OS/390 and MVS; provides JES2/3, RACF security, JCL batch, and UNIX System Services (POSIX environment).</td><td>Enterprise workloads on IBM Z mainframes; partitioned datasets, CICS/IMS, and USS shells.</td></tr><tr><td>ZFS</td><td>Zettabyte File System â advanced filesystem/volume manager with snapshots, checksums, compression, and COW semantics.</td><td>Create ZFS datasets/pools; instant snapshots/<code>zfs send</code> replication.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>A/UX</td><td>Apple UNIX â Apple's early implementation of Unix for their 68k-based Macintosh computers, featuring a Mac-like GUI.</td><td>
1An early attempt to merge the Mac GUI with a POSIX-compliant Unix kernel.</td></tr><tr><td>ACP</td><td>Airline Control Program â IBM's specialized high-throughput transaction processing operating system for System/360 and System/370, engineered for airline reservations and other real-time industries; predecessor to TPF.</td><td>Run on IBM mainframes to power reservation systems; later evolved into the Transaction Processing Facility (TPF).</td></tr><tr><td>CDE</td><td>Common Desktop Environment â classic UNIX desktop environment based on Motif and the X Window System; widely used on commercial UNIX workstations in the 1990s.</td><td>HPâUX, Solaris, AIX shipped CDE as the default desktop; superseded by GNOME/KDE.</td></tr><tr><td>COFF</td><td>Common Object File Format â early, influential format for executables and object files on Unix-like systems.</td><td>Predecessor to ELF and PE; used in early System V.</td></tr><tr><td>CP/CMS</td><td>Control Program / Cambridge Monitor System â IBM's experimental virtualization-focused time-sharing system for the System/360 Model 67, pairing a hypervisor (CP) with per-user CMS interactive environments.</td><td>Demonstrated full virtual machines hosting guest OSes; evolved into VM/370 and laid the groundwork for modern IBM mainframe virtualization.</td></tr><tr><td>CP/M</td><td>Control Program for Microcomputers â early microcomputer OS preceding MSâDOS.</td><td>1970s/80s 8âbit systems running CP/M.</td></tr><tr><td>CTSS</td><td>Compatible Time-Sharing System â pioneering time-sharing OS developed at MIT for the IBM 7090/7094; introduced concepts like password logins and interactive command shells; precursor to MULTICS.</td><td>MIT Project MAC on IBM 7094; early 1960s interactive computing.</td></tr><tr><td>DG/UX</td><td>Data General's UNIX for AViiON servers/workstations; SVR4-based, multi-processor support; discontinued.</td><td>DG AViiON systems running DG/UX; enterprise UNIX of the 1990s.</td></tr><tr><td>DOS</td><td>Disk Operating System â family of diskâbased OSes.</td><td>MSâDOS, PCâDOS, DRâDOS.</td></tr><tr><td>DTSS</td><td>Dartmouth Time-Sharing System â early time-sharing operating system co-developed with the Dartmouth BASIC language to provide interactive computing access to students and faculty.</td><td>Students logged into DTSS terminals to run BASIC programs; influenced later educational and commercial time-sharing services.</td></tr><tr><td>EMS</td><td>Expanded Memory Specification â paged memory technique (bank switching) to access >1MB of RAM on 8086/286 PCs in real mode via a 64KB page frame in the UMA.</td><td>Lotus/Intel/Microsoft (LIM) EMS; configure with EMM386.EXE for DOS games/apps.</td></tr><tr><td>GCOS</td><td>General Comprehensive Operating System â Honeywell/Bull mainframe OS originally launched as GECOS (General Electric Comprehensive Operating Supervisor), known for robust batch and transaction processing.</td><td>Unix <code>/etc/passwd</code> "gecos" field traces back to GCOS interoperability; enterprises still run GCOS on Bull mainframes.</td></tr><tr><td>GEM</td><td>Graphics Environment Manager â a WIMP-style GUI from Digital Research, used on the Atari ST and Amstrad PCs.</td><td>The GEM desktop environment; competitor to early Mac OS and Windows.</td></tr><tr><td>GEOS</td><td>Graphic Environment Operating System â a GUI-based operating system for 8-bit home computers and later for PCs.</td><td>Popular on the Commodore 64; PC/GEOS was an alternative to early Windows.</td></tr><tr><td>HMA</td><td>High Memory Area â the first ~64KB of extended memory, made accessible in real mode on 286+ CPUs by manipulating the A20 line.</td><td>Load DOS into the HMA (<code>DOS=HIGH</code>) to free up conventional memory.</td></tr><tr><td>IRIX</td><td>SGI's UNIX for MIPS workstations/servers; renowned for graphics and the original home of XFS; discontinued.</td><td>SGI Octane/Onyx systems running IRIX; MIPSpro toolchain; legacy SGI graphics stacks.</td></tr><tr><td>ITS</td><td>Incompatible Timesharing System â MIT'
1s hacker-centric time-sharing OS for the PDP-6 and PDP-10 that introduced extensible systems, open access, and influential developer culture.</td><td>Hackers ran ITS on MIT AI Lab PDP-10s; today enthusiasts explore it via SIMH/KA/KI/KL emulators.</td></tr><tr><td>LM</td><td>LAN Manager â a network operating system (NOS) developed by Microsoft and 3Com, a predecessor to Windows NT Server.</td><td>Competed with Novell NetWare; ran on OS/2.</td></tr><tr><td>MFT</td><td>Multiprogramming with a Fixed number of Tasks â an early configuration of IBM's OS/360 that managed a fixed number of concurrent jobs in static memory partitions.</td><td>One of the primary OS/360 options alongside MVT (Variable number of Tasks).</td></tr><tr><td>MP/M</td><td>Multiprogramming Monitor for Microprocessors â a multi-user version of the CP/M operating system.</td><td>Early 8-bit multi-user business systems; predecessor to Concurrent CP/M.</td></tr><tr><td>MULTICS</td><td>Multiplexed Information and Computing Service â ambitious time-sharing OS jointly developed by MIT, Bell Labs, and GE, pioneering concepts like hierarchical file systems, ring-based security, and dynamic linking.</td><td>Ran on GE-645/Honeywell machines; inspired UNIX and modern OS designs; notable for shared memory segments and user ring protection.</td></tr><tr><td>MULTICS</td><td>Multiplexed Information and Computing Service â influential timeâsharing OS from MIT/GE/Bell Labs that inspired many UNIX concepts.</td><td>1960s/70s mainframes; security and modular design influenced Unix.</td></tr><tr><td>MVS</td><td>Multiple Virtual Storage â mainstream IBM mainframe OS from the System/370 era onward, providing robust batch and transaction processing; evolved into OS/390 and z/OS.</td><td>Run CICS/IMS transactions; submit JCL batch jobs; manage DASD with VSAM.</td></tr><tr><td>MVT</td><td>Multiprogramming with a Variable number of Tasks â a configuration of IBM's OS/360 that was a precursor to MVS, allowing for a dynamic number of concurrent jobs.</td><td>One of the primary OS/360 options alongside MFT (Fixed number of Tasks).</td></tr><tr><td>NLM</td><td>NetWare Loadable Module â a server module (driver, application, or utility) that could be dynamically loaded and unloaded in the Novell NetWare operating system.</td><td><code>.NLM</code> files for drivers and server applications on a NetWare server.</td></tr><tr><td>OS/2</td><td>IBM/Microsoft then IBM OS succeeding DOS.</td><td>OS/2 Warp on 1990s PCs.</td></tr><tr><td>OS/360</td><td>Operating System/360 â IBM's influential mainframe OS for the System/360, introducing concepts like JCL, partitioned datasets, and a family of compatible systems.</td><td>Run batch jobs with JCL; manage datasets on DASD; MFT/MVT variants.</td></tr><tr><td>OS/370</td><td>Operating System/370 â successor to OS/360 for System/370 mainframes, introducing virtual memory (SVS/MVS).</td><td>MVS (Multiple Virtual Storage) became the mainstream OS/370 version.</td></tr><tr><td>OS/390</td><td>Successor to MVS/ESA, integrating UNIX services (USS) and other modern features into the core mainframe OS; predecessor to z/OS.</td><td>Run UNIX and batch workloads on the same system; prepare for Y2K.</td></tr><tr><td>OSF/1</td><td>Open Software Foundation's UNIX, later Digital UNIX/Tru64; SVR4-based with Mach kernel components and advanced features.</td><td>DEC Alpha systems running Digital UNIX; TruCluster high-availability.</td></tr><tr><td>PLATO</td><td>Programmed Logic for Automatic Teaching Operations â pioneering computer-based education system with touch-enabled terminals, graphical courseware, and early online community features (forums, chat).</td><td>University of Illinois' PLATO IV terminals delivered interactive lessons and multiplayer games; influenced modern e-learning and social computing.</td></tr><tr><td>RISC OS</td><td>Acorn's desktop operating system for ARM-based Archimedes and Risc PC machines, featuring a WIMP interface and cooperative multitasking.</td><td>Run on Acorn Archimedes/Risc PC systems; modern builds run RISC OS Open on Raspberry Pi.</td></tr><tr><td>RSTS</td><td>Resource Sharing Time-Sharing â DEC's multi-user PDP-11 operating system that merged RT-11 friendliness with RSX services for schools and business computing.</td><td>Boot RSTS/E on a PDP-11 or under SIMH to run BASIC, COBOL, and timeshared workloads.</td></tr><tr><td>RSX</td><td>Real-Time System Executive â DEC's multi-user, multitasking real-time operating system family for PDP-11 minicomputers.</td><td>Run RSX-11M/RSX-11M-Plus on PDP-11 hardware or via SIMH for industrial
1control and retrocomputing.</td></tr><tr><td>RT-11</td><td>Real-Time 11 â DEC's single-user real-time operating system for PDP-11 minicomputers, optimized for lab automation and embedded control.</td><td>Load RT-11 from floppy/disk on PDP-11 hardware or run under SIMH for vintage development.</td></tr><tr><td>SABRE</td><td>Semi-Automated Business Research Environment â American Airlines/IBM's pioneering real-time airline reservation system derived from SAGE concepts.</td><td>Early 1960s SABRE mainframes booked flights via networked agent terminals; evolved into modern Sabre GDS platforms.</td></tr><tr><td>SAGE</td><td>Semi-Automatic Ground Environment â Cold War-era air defense system combining massive AN/FSQ-7 computers, radar feeds, and real-time command software to track aircraft and coordinate intercepts.</td><td>1950s USAF direction centers ran SAGE consoles and radar plots; preserved today via simulations and museum restorations.</td></tr><tr><td>SVR4</td><td>System V Release 4 â AT&T/Sun UNIX unifying System V, BSD, and Xenix features; foundation for many 1990s commercial UNIXes.</td><td>Solaris 2.x and UnixWare derive from SVR4 with STREAMS networking and SVR4 package tools.</td></tr><tr><td>TENEX</td><td>TEN Executive â BBN's influential PDP-10 time-sharing operating system introducing demand paging, virtual memory, and ARPANET innovations that fed directly into DEC's TOPS-20.</td><td>Early ARPANET nodes ran TENEX; features like the Exec shell, JSYS calls, and paging hardware shaped later TOPS-20 and other networked OSes.</td></tr><tr><td>TOPS</td><td>Total Operating System â DEC's time-sharing operating systems for the PDP-10/DECsystem-10 (TOPS-10) and DECsystem-20 (TOPS-20), foundational during the ARPANET era.</td><td>Explore TOPS-10/TOPS-20 on emulated DECsystem hardware; develop with ITS-style monitors and early networking tools.</td></tr><tr><td>TSR</td><td>Terminate and Stay Resident â DOS resident utility/program.</td><td>Keyboard macros/clock TSRs in MS-DOS.</td></tr><tr><td>TSS/360</td><td>Time Sharing System/360 â IBM's ambitious but troubled time-sharing operating system for the System/360 Model 67, introducing virtual memory and interactive access; lessons informed later VM/370.</td><td>Provided remote terminal access on S/360-67 with DAT hardware; performance/complexity issues led IBM to focus on successor systems.</td></tr><tr><td>UMA</td><td>Upper Memory Area â the memory block between 640KB and 1MB on PCs, used for system BIOS, option ROMs, and video memory; free portions (UMBs) could map drivers/TSRs.</td><td>Load drivers high with <code>DEVICEHIGH</code> in <code>CONFIG.SYS</code> to free conventional memory.</td></tr><tr><td>VAXELN</td><td>VAX Embedded Local Network â DEC's real-time operating system for VAX systems that provided networked, event-driven control applications with VMS tooling.</td><td>Build VAXELN images on VMS hosts and deploy to VAX hardware or emulators for industrial automation use cases.</td></tr><tr><td>VM/370</td><td>Virtual Machine/370 â IBM's first official release of the VM hypervisor for the System/370, a landmark in virtualization.</td><td>Predecessor to later VM/ESA and z/VM systems.</td></tr><tr><td>VM/CMS</td><td>Virtual Machine / Conversational Monitor System â the combination of the VM hypervisor and its single-user interactive CMS operating system.</td><td>The primary user experience on IBM mainframe time-sharing systems.</td></tr><tr><td>VMS</td><td>Virtual Memory System â DEC's operating system for VAX (later Alpha/Itanium as OpenVMS), featuring robust clustering and security.</td><td>VAX/VMS in enterprises; OpenVMS clusters with RMS/DCL.</td></tr><tr><td>WAITS</td><td>Stanford's timesharing system â derived from SAIL's modifications to DEC's TOPS-10 for PDP-10s, adding advanced editing, graphics, and music tooling that influenced interactive computing.</td><td>Hosted SAIL's AI research tools, graphical displays, and early computer music systems; many WAITS ideas migrated back into TOPS-10/TOPS-20 ecosystems.</td></tr><tr><td>WfW</td><td>Windows for Workgroups â an early version of Microsoft Windows that integrated peer-to-peer networking directly into the OS.</td><td>Windows 3.11 for Workgroups with File and Print Sharing.</td></tr><tr><td>XMS</td><td>Extended Memory Specification â standard for DOS programs to access extended memory (>1MB) on 286+ CPUs via a driver (HIMEM.SYS) and A20 gate control.</td><td>Load DOS high (<code>DOS=HIGH</code>); use XMS for RAM disks and apps needing large buffers.</td></tr></tbody></table><h2 id="document-markup" tabindex="-1"><a class="header-anchor" href="#document-markup"><span>Document Markup</span></a></h2><table><thead><tr><th>
1Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>LaTeX</td><td>Document preparation system built on TeX that provides highâlevel markup for typesetting complex documents (sections, figures, bibliographies) with excellent math support.</td><td>Write papers/books with LaTeX classes/packages; <code>pdflatex</code>/<code>xelatex</code> build pipelines.</td></tr><tr><td>MD</td><td>Markdown â lightweight plainâtext markup language for formatting documents with simple syntax for headings, lists, emphasis, links, and code.</td><td><code>README.md</code>, GitHub Flavored Markdown; code fences <code></code> and tables in docs/blogs.</td></tr><tr><td>RST</td><td>reStructuredText â plaintext markup language used in the Python ecosystem and Sphinx documentation generator; emphasizes readable source and structured directives.</td><td>Sphinx <code>.rst</code> docs with directives/roles; PyPI/ReadTheDocs project documentation.</td></tr><tr><td>TeX</td><td>Lowâlevel typesetting system designed by Donald Knuth providing precise control over layout and mathematics; foundation for LaTeX and many formats.</td><td>Typeset math-heavy documents; <code>plain TeX</code> macros; outputs DVI/PDF via engines like pdfTeX/XeTeX/LuaTeX.</td></tr><tr><td>XML</td><td>Extensible Markup Language â verbose structured data.</td><td>XML configs, SOAP payloads.</td></tr><tr><td>XSLT</td><td>Extensible Stylesheet Language Transformations â declarative language for transforming XML documents using template rules, XPath selection, and functions.</td><td>Transform DocBook/XML to HTML/PDF with Saxon/Xalan; XSLT 1.0/2.0/3.0.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>DTD</td><td>Document Type Definition â schema language defining the legal structure/elements/attributes of SGML/XML documents.</td><td>Validate XML with a DTD; <code><!DOCTYPE ...></code> declarations; legacy vs XML Schema/Relax NG.</td></tr><tr><td>XSD</td><td>XML Schema Definition â the W3C standard for defining the structure and data types of XML documents; the powerful successor to DTD.</td><td>Validate XML against an <code>.xsd</code> schema; generate code from schemas.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>SGML</td><td>Standard Generalized Markup Language â meta-language for defining markup languages; foundation for HTML/XML; rarely used directly today.</td><td>SGML-based HTML 2.0/3.2 era; modern stacks use XML/HTML5 instead.</td></tr></tbody></table><h2 id="file-formats" tabindex="-1"><a class="header-anchor" href="#file-formats"><span>File Formats</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AAC</td><td>Advanced Audio Coding â a lossy audio compression format that is the successor to MP3, offering better quality at similar bitrates.</td><td>Standard audio format for YouTube, Apple devices, and digital video broadcasting.</td></tr><tr><td>CAB</td><td>Cabinet archive â Microsoft compressed archive format that supports embedded digital signatures and is commonly used to bundle Windows drivers, updates, and setup payloads.</td><td>Windows Update distributions and driver packages ship <code>.cab</code> files; <code>expand</code> or <code>DISM</code> extracts them.</td></tr><tr><td>CHM</td><td>Compiled HTML Help â Microsoft compressed archive format packaging HTML, images, and navigation for offline help files, typically viewed via the WinHelp system.</td><td>Windows applications shipped <code>.chm</code> manuals; <code>hh.exe</code> opens them; security hardening blocks untrusted CHMs.</td></tr><tr><td>DVI</td><td>Device Independent file format â TeX's output format describing pages and typeset content in a deviceâagnostic way, later converted to PostScript/PDF or displayed via drivers.</td><td>Generate <code>.dvi</code> from TeX; view/convert with <code>dvips</code>, <code>dvipdfmx</code>, or viewers like xdvi.</td></tr><tr><td>EPUB</td><td>Electronic Publication â a popular open standard for e-books, using web technologies like HTML, CSS, and SVG.</td><td>Read <code>.epub</code> files on an e-reader or with a software viewer.</td></tr><tr><td>ICO</td><td>Icon file format â container for one or more images in various sizes/color depths, used for favicons and application icons.</td><td><code>favicon.ico</code> in the web root; Windows <code>.exe</code> icon resources.</td></tr><tr><td>INF</td><td>Setup Information file â plain-text configuration scripts that drive Windows installation and configuration of drivers, services, and components.</td><td>Windows driver packages ship <code>.inf</code> files consumed by SetupAPI; <code>pnputil</code> adds or stages them.</td></tr><tr><td>INI</td><td>Initialization file â simple key/value configuration format organized into sections for Windows applications and many cross-platform tools.</td><td><code>.ini</code> files under <code>%WINDIR%</code> or alongside apps; parsed by <code>
1GetPrivateProfileString</code>/config libraries.</td></tr><tr><td>MSI</td><td>Microsoft Installer package â database-backed installation package format used by Windows Installer to deploy applications, updates, and patches.</td><td>Enterprise software ships <code>.msi</code> packages; <code>msiexec</code> installs/uninstalls with logging and transforms.</td></tr><tr><td>OTF</td><td>OpenType Font â cross-platform font format that can contain PostScript or TrueType outlines and supports advanced typographic features.</td><td><code>.otf</code> fonts for professional typography; supersedes PostScript Type 1.</td></tr><tr><td>PNG</td><td>Portable Network Graphics â lossless raster image format with DEFLATE compression, alpha transparency, and gamma/metadata support.</td><td><code>.png</code> UI assets/screenshots; better compression than BMP; supports transparency.</td></tr><tr><td>PS</td><td>PostScript â page description language and programming language used primarily in desktop publishing and printing workflows.</td><td>Generate vector/print-ready <code>.ps</code> files; printers interpret PostScript directly; PDF evolved from it.</td></tr><tr><td>SVG</td><td>Scalable Vector Graphics â XML-based vector image format for resolution-independent graphics.</td><td>Inline icons/diagrams in HTML; CSS/SMIL animations.</td></tr><tr><td>TOML</td><td>Tom's Obvious, Minimal Language â minimal configuration format with clear semantics.</td><td><code>pyproject.toml</code>, <code>Cargo.toml</code> tool configs.</td></tr><tr><td>TTF</td><td>TrueType Font â outline font format using quadratic Bézier curves; widely supported across operating systems and browsers.</td><td><code>.ttf</code> fonts for desktop/web (often inside <code>.ttc</code> collections or wrapped as WOFF/WOFF2 for the web).</td></tr><tr><td>WOFF</td><td>Web Open Font Format â compressed container format for web fonts (TrueType/OpenType), enabling faster delivery; WOFF2 offers improved compression.</td><td>Serve <code>.woff2</code> with a <code>.woff</code> fallback for modern web typography.</td></tr><tr><td>YAML</td><td>Human-friendly serialization format.</td><td><code>docker-compose.yml</code> files.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>BMP</td><td>Bitmap Image File â raster image format (DeviceâIndependent Bitmap) storing pixel data with optional RLE compression.</td><td><code>.bmp</code> screenshots/icons; large files compared to PNG/JPEG.</td></tr><tr><td>GIF</td><td>Graphics Interchange Format â legacy lossless raster image format limited to 256 colors, best known for supporting simple animations.</td><td>Animated memes; superseded by PNG for static images and APNG/video for complex animations.</td></tr><tr><td>MP3</td><td>MPEG-1 Audio Layer III â a popular lossy audio compression format that revolutionized digital music.</td><td><code>.mp3</code> files for music; superseded by AAC but still widely used.</td></tr><tr><td>RTF</td><td>Rich Text Format â plain-text document format with markup (control words and groups) for character/paragraph styling; widely supported across editors.</td><td>Save/export <code>.rtf</code> from word processors to interchange formatted text.</td></tr></tbody></table><h2 id="data-encodings" tabindex="-1"><a class="header-anchor" href="#data-encodings"><span>Data Encodings</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>ASCII</td><td>American Standard Code for Information Interchange â 7âbit character encoding defining codes 0â127; subset of UTFâ8.</td><td>Plain ASCII text files; printable characters and control codes.</td></tr><tr><td>BOM</td><td>Byte Order Mark â optional Unicode signature at the start of a text stream indicating endianness/encoding (UTFâ8/UTFâ16/UTFâ32).</td><td>Avoid UTFâ8 BOM in Unix scripts; UTFâ16 LE files start with FE FF.</td></tr><tr><td>CRLF</td><td>Carriage Return + Line Feed â sequence <code>\\r\\n</code> used by Windows and many network protocols as a line terminator.</td><td>HTTP headers and CSV on Windows use CRLF line endings.</td></tr><tr><td>DER</td><td>Distinguished Encoding Rules â binary ASN.1 encoding used for certificates/keys.</td><td><code>.cer/.der</code> X.509 certs; binary form of ASN.1 structures.</td></tr><tr><td>EBCDIC</td><td>Extended Binary Coded Decimal Interchange Code â 8âbit character encoding used primarily on IBM mainframes; incompatible with ASCII.</td><td>Converting EBCDIC files to ASCII/UTFâ8 when integrating with mainframe systems.</td></tr><tr><td>GUID</td><td>Globally Unique Identifier â Microsoftâs term for UUID.</td><td><code>{3F25...C3301}</code> COM-style format.</td></tr><tr><td>LF</td><td>Line Feed â newline control character (0x0A) used by Unix/Linux/macOS to terminate lines.</td><td><code>\\n</code> in text files; contrast with CR (0x0D) and CRLF (<code>\\r\\n</code>).</td></tr><tr><td>MIME</td><td>Multipurpose Internet Mail Extensions â standardized media types and encoding for content on the internet.</td><td><code>Content-Type: application/json</code>; <code>multipart/form-data</code> with boundaries.</td></tr><tr><td>PEM</td><td>Privacy-Enhanced Mail â Base64 (PEM) encoding with header/footer lines for certs/keys.</td><td><code>-----BEGIN CERTIFICATE-----</code> blocks; <code>.pem/.crt/.key</code> files.</td></tr><tr><td>UCS</td><td>Universal Character Set â ISO/IEC 10646 standard defining the full repertoire of Unicode code points; Unicode is kept synchronized with UCS.</td><td>UCS-2/UCS-4 historical encodings map to UTFâ16/UTFâ32; code points vs encodings distinction.</td></tr><tr><td>UTF</td><td>Unicode Transformation Format â encodings of Unicode code points (e.g., UTFâ8/UTFâ16/UTFâ32).
1</td><td>UTFâ8 is the dominant encoding on the web and in APIs.</td></tr><tr><td>UUID</td><td>Universally Unique Identifier â 128-bit unique ID.</td><td>UUID v4 random, v5 namespace.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>BCD</td><td>Binary-Coded Decimal â encoding that represents each decimal digit with its own binary nibble (4 bits), enabling precise decimal arithmetic.</td><td>Packed BCD in financial systems; CPU decimal adjust instructions (DAA/DAS).</td></tr><tr><td>MBCS</td><td>Multi-Byte Character Set â legacy variable-length encodings that use one or more bytes per character (often DBCS for CJK) prior to widespread Unicode adoption.</td><td>Windows "ANSI" code pages (Shift_JIS, EUCâJP); prefer UTFâ8 today.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>CR</td><td>Carriage Return â control character (0x0D) historically used to move the print head to column 0; used by classic Mac OS as line terminator.</td><td><code>\\r</code> in classic Mac text files; pairs with LF in CRLF on Windows.</td></tr></tbody></table><h2 id="data-formats-interchange" tabindex="-1"><a class="header-anchor" href="#data-formats-interchange"><span>Data Formats (Interchange)</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>BSON</td><td>Binary JSON â binary serialization format with typed fields and efficient encoding designed for fast traversal and in-place updates.</td><td>MongoDB wire/storage format; supports types like ObjectId, Date, binary; drivers encode/decode BSON.</td></tr><tr><td>CBOR</td><td>Concise Binary Object Representation â compact, schema-optional binary data format designed for small code and message size (RFC 8949).</td><td>IoT/API payloads with maps/arrays; COSE for CBOR Object Signing and Encryption; diagnostic notation for debugging.</td></tr><tr><td>CSV</td><td>Comma-Separated Values â plain text tabular format.</td><td><code>users.csv</code> exports/imports.</td></tr><tr><td>HDF5</td><td>Hierarchical Data Format version 5 â portable file format and library for storing large, complex, heterogeneous scientific data with groups/datasets and rich metadata.</td><td>Store arrays/tables/images with chunking/compression; used in scientific computing and ML datasets.</td></tr><tr><td>JSON</td><td>JavaScript Object Notation â data format.</td><td><code>{ "id": 1 }</code> payloads.</td></tr><tr><td>JSON-LD</td><td>JSON for Linking Data â JSONâbased serialization for Linked Data/RDF that uses <code>@context</code> to map terms to IRIs and add semantics to JSON documents.</td><td>Embed schema.org with <code><script type="application/ld+json"></code> on web pages; exchange RDF graphs in JSON for knowledge graphs/APIs.</td></tr><tr><td>JSONL</td><td>JSON Lines â newlineâdelimited JSON records for streaming/appendâfriendly logs and datasets (aka NDJSON).</td><td>One JSON object per line; easy to process with lineâoriented tools.</td></tr><tr><td>netCDF</td><td>Network Common Data Form â selfâdescribing, portable data formats and libraries for arrayâoriented scientific data; supports classic (CDF), 64âbit offset, and netCDFâ4/HDF5.</td><td>Earth science datasets (grids/time series); interoperable with many scientific tools.</td></tr><tr><td>ORC</td><td>Optimized Row Columnar â columnar storage format optimized for analytics with predicate pushdown, compression, and statistics.</td><td>Store big data tables in ORC on Hadoop/Spark; efficient scans and compression.</td></tr><tr><td>OWL</td><td>Web Ontology Language â a family of knowledge representation languages for authoring ontologies, based on RDF and standardized by the W3C.</td><td>Define classes, properties, and relationships for a domain in an ontology.</td></tr><tr><td>RDF</td><td>Resource Description Framework â W3C model for describing and linking data using triples (subjectâpredicateâobject), often serialized as Turtle/RDF/XML/JSONâLD.</td><td>Knowledge graphs, linked data; schema.org markup via JSONâLD.</td></tr><tr><td>RDFS</td><td>RDF Schema â a vocabulary for defining classes and properties for RDF data, providing a basic ontology framework.</td><td><code>rdfs:Class</code>, <code>rdfs:subClassOf</code>, <code>rdfs:domain</code>, <code>rdfs:range</code>.</td></tr><tr><td>SKOS</td><td>Simple Knowledge Organization System â a W3C standard for representing knowledge organization systems like thesauruses and taxonomies.</td><td>Define concepts with <code>skos:Concept</code> and relationships like <code>skos:broader</code>.</td></tr><tr><td>SPARQL</td><td>
1SPARQL Protocol and RDF Query Language â the standard query language for RDF databases (triple stores).</td><td><code>SELECT ?s ?p ?o WHERE { ?s ?p ?o }</code> to query a graph.</td></tr><tr><td>TSV</td><td>Tab-Separated Values â plain text tabular format using tabs as delimiters.</td><td><code>users.tsv</code> exports with tabâdelimited fields.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>FOAF</td><td>Friend of a Friend â one of the earliest and most famous Semantic Web ontologies, used to describe people and their relationships.</td><td>Define a person's profile using <code>foaf:Person</code>, <code>foaf:name</code>, <code>foaf:knows</code>.</td></tr><tr><td>JSONP</td><td>JSON with Padding â legacy technique to circumvent sameâorigin policy by wrapping JSON in a callback for script tags.</td><td><code>callback({ ... })</code> responses consumed via <code><script></code>; replaced by CORS.</td></tr><tr><td>MARC</td><td>Machine-Readable Cataloging â a standard for the representation and communication of bibliographic and related information in machine-readable form.</td><td>Library automation systems use MARC records to manage catalogs.</td></tr><tr><td>RSS</td><td>Really Simple Syndication â XML-based web feed format for publishing updates.</td><td>Blog feed at <code>/feed.xml</code>; subscribe in a feed reader.</td></tr></tbody></table><h2 id="data-formats-compression-archival" tabindex="-1"><a class="header-anchor" href="#data-formats-compression-archival"><span>Data Formats (Compression & Archival)</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>7z</td><td>7âZip archive format â open archive container supporting solid compression, advanced filters, and high ratios via LZMA/LZMA2 and others.</td><td>Create/extract with <code>7z a archive.7z files/</code> and <code>7z x</code>; widely used for highâratio packaging.</td></tr><tr><td>BZIP2</td><td>BurrowsâWheeler block-sorting compressor â high compression ratio with moderate CPU cost; slower than gzip, faster than xz in many cases.</td><td>Compress archives/logs: <code>bzip2 file</code>, <code>tar -cjf archive.tar.bz2 dir/</code>; <code>.bz2</code> packages.</td></tr><tr><td>DEFLATE</td><td>Lossless compression format combining LZ77 slidingâwindow dictionary with Huffman coding; ubiquitous in ZIP, gzip, and PNG.</td><td>Compress HTTP responses (<code>ContentâEncoding: gzip/deflate</code>), ZIP entries, and PNG image data.</td></tr><tr><td>GZIP</td><td>GNU Zip â widely used lossless compression format using DEFLATE (LZ77+Huffman); good balance of speed and ratio.</td><td>Compress streams/files: <code>gzip file</code>, <code>tar -czf archive.tar.gz dir/</code>; HTTP <code>Content-Encoding: gzip</code>.</td></tr><tr><td>JAR</td><td>Java ARchive â ZIPâbased archive format for packaging Java classes/resources and metadata (<code>META-INF/MANIFEST.MF</code>); supports signing and classâpath entries.</td><td>Build/run <code>.jar</code> apps (<code>jar cfm app.jar MANIFEST.MF -C out/ .</code>); libraries on the classpath; fat/uber JARs bundle deps.</td></tr><tr><td>LZ4</td><td>Extremely fast lossless compression algorithm optimized for speed with modest compression ratios.</td><td>Compress logs/IPC payloads with LZ4 for low latency; <code>.lz4</code> frames.</td></tr><tr><td>LZ77</td><td>LempelâZiv 1977 â dictionary-based lossless compression using a sliding window and backâreferences (length, distance) to past data.</td><td>Foundation for DEFLATE (gzip/ZIP) and many formats; emits literals and copy tokens.</td></tr><tr><td>LZMA</td><td>LempelâZivâMarkov chain Algorithm â highâratio lossless compression with larger memory use and slower speeds than DEFLATE; foundation for 7z and XZ (LZMA2).</td><td>Create 7z archives with LZMA/LZMA2; <code>xz</code> uses LZMA2 for <code>.xz</code>/<code>.tar.xz</code>.</td></tr><tr><td>RAR</td><td>Roshal Archive â proprietary archive format supporting solid compression, recovery records, and strong encryption; widely used but not fully open.</td><td>Create/extract with WinRAR/<code>rar</code>/<code>unrar</code>; <code>.rar</code> multiâpart volumes; consider 7z/zip for openness.</td></tr><tr><td>RLE</td><td>Run-Length Encoding â simple lossless compression that replaces runs of repeated symbols with a count and value.</td><td>Bitmap/scanline compression (e.g., BMP RLE, fax/CCITT variants); good for large uniform areas.</td></tr><tr><td>TAR</td><td>Tape ARchive â stream/archive format that bundles multiple files/directories with metadata into a single sequential archive; often compressed (e.g., .tar.gz/.tgz).</td><td>Create/extract backups: <code>tar -czf backup.tgz dir/</code>; used for packaging and distribution.</td></tr><tr><td>XZ</td><td>XZ Utils format â highâratio lossless compression using LZMA2 with solid archives and strong compression at the cost of CPU/time.</td><td>Compress release artifacts/logs: <code>tar -cJf</code>, <code>xz -T0 file</code>; <code>.tar.xz</code> packages in Linux distros.</td></tr><tr><td>ZIP</td><td>ZIP archive format â ubiquitous container supporting perâfile compression (typically DEFLATE), random access, and metadata; widely supported on all platforms.</td><td><code>.zip</code> files; <code>zip</code>/<code>unzip</code>; JAR/APK/Office Open XML use ZIP containers.</td></tr><tr><td>ZSTD</td><td>Zstandard â modern fast lossless compression algorithm offering high ratios with very high decompression speed; supports dictionaries.</td><td>Compress artifacts/logs with zstd; <code>.zst</code> files; use dictionaries for small data.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>LZW</td><td>LempelâZivâWelch â dictionary-based lossless compression algorithm historically used in GIF and some TIFF variants; now patent-free.</td><td>Classic GIF image compression; replace with PNG for lossless images.</td></tr></tbody></table><h2 id="data-processing" tabindex="-1"><a class="header-anchor" href="#data-processing"><span>Data Processing</span></a></h2><table><thead><tr><th>
1Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>ACID</td><td>Atomicity, Consistency, Isolation, Durability â transaction guarantees.</td><td>Bank transfer completes fully or not at all.</td></tr><tr><td>ADO.NET</td><td>ActiveX Data Objects .NET â the modern data access framework for the .NET platform, succeeding classic ADO.</td><td><code>SqlConnection</code> and <code>DataSet</code> for database operations in C#/VB.NET.</td></tr><tr><td>BASE</td><td>Basically Available, Soft state, Eventual consistency â distributed tradeoff.</td><td>Eventual consistency across regions.</td></tr><tr><td>BI</td><td>Business Intelligence â processes/tools to analyze business data for insights and decisionâmaking.</td><td>Dashboards and reports in Looker/Power BI over a warehouse.</td></tr><tr><td>BLOB</td><td>Binary Large Object â large binary field in a DB.</td><td>Store images/files as BLOBs or in object storage.</td></tr><tr><td>CAP</td><td>Consistency, Availability, Partition tolerance â favor two under partition.</td><td>AP systems may return stale data during splits.</td></tr><tr><td>CBO</td><td>Cost-Based Optimizer â query planner that chooses execution plans by estimating cost using statistics.</td><td>Analyze stats; planner picks index scan vs full scan.</td></tr><tr><td>CDC</td><td>Change Data Capture â stream DB changes.</td><td>Debezium publishes events to Kafka.</td></tr><tr><td>CRDT</td><td>Conflict-free Replicated Data Type â data structures that merge deterministically without coordination for eventual consistency.</td><td>LWW-Element-Set, G-Counter; collaborative docs with Automerge/Yjs.</td></tr><tr><td>CTE</td><td>Common Table Expression â named temporary result set referenced within a statement.</td><td><code>WITH recent AS (SELECT ...) SELECT * FROM recent WHERE ...</code>.</td></tr><tr><td>DB</td><td>Database â organized data managed by a DBMS.</td><td>Postgres/MySQL database with tables, indexes, and transactions.</td></tr><tr><td>DB2</td><td>DB2 â IBM's family of relational database management systems (RDBMS) running on platforms from Linux/Unix/Windows to mainframes (z/OS).</td><td>Enterprise data warehousing and OLTP on DB2 for z/OS or LUW.</td></tr><tr><td>DBMS</td><td>Database Management System â software that manages databases, provides storage, query, and transaction processing.</td><td>PostgreSQL, MySQL, SQLite, Oracle, SQL Server.</td></tr><tr><td>DDL</td><td>Data Definition Language â SQL for defining/modifying schema objects.</td><td><code>CREATE TABLE</code>, <code>ALTER TABLE</code>, <code>CREATE INDEX</code>.</td></tr><tr><td>DLQ</td><td>Dead Letter Queue â holding queue/topic for messages/events that could not be processed or delivered after retries, isolating poison messages for inspection and remediation.</td><td>SQS redrive policy sends failed messages to a DLQ; Kafka error/"-dlq" topic.</td></tr><tr><td>DML</td><td>Data Manipulation Language â SQL for querying and changing data.</td><td><code>SELECT</code>, <code>INSERT</code>, <code>UPDATE</code>, <code>DELETE</code>.</td></tr><tr><td>DW</td><td>Data Warehouse â centralized, integrated repository optimized for analytics.</td><td>Snowflake/BigQuery/Redshift with star/snowflake schemas.</td></tr><tr><td>EF</td><td>Entity Framework â Microsoft's object-relational mapping (ORM) framework for .NET.</td><td>Map database tables to C# objects with EF Core; use LINQ to query data.</td></tr><tr><td>ELT</td><td>Extract, Load, Transform â load raw data then transform in the warehouse.</td><td>Modern ELT with dbt/BigQuery.</td></tr><tr><td>ERD</td><td>Entity Relationship Diagram â visual schema modeling notation that captures entities, their attributes, and relationships/cardinalities before implementing a database.</td><td>Sketch an ERD in crow's-foot notation to model <code>Customer</code>â<code>Order</code>â<code>OrderLine</code> relationships prior to creating tables.</td></tr><tr><td>ETL</td><td>Extract, Transform, Load â data integration pipeline.</td><td>Batch load to data warehouse.</td></tr><tr><td>FK</td><td>
1Foreign Key â constraint that enforces referential integrity by requiring values to exist in a referenced table.</td><td><code>orders.user_id</code> references <code>users.id</code>; ON DELETE CASCADE.</td></tr><tr><td>GIS</td><td>Geographic Information System â system for capturing, storing, analyzing, and managing spatial or geographic data.</td><td>Analyze spatial data with ArcGIS or QGIS; build location-aware apps.</td></tr><tr><td>HLL</td><td>HyperLogLog â probabilistic algorithm for cardinality (distinct count) estimation that uses fixed, small memory with tunable relative error via stochastic averaging of leading-zero counts.</td><td>Approximate unique users/events with ~1â2% error using kilobytes of memory; streaming distinct counts in analytics pipelines.</td></tr><tr><td>LSMT</td><td>Log-Structured Merge-Tree â write-optimized indexing/storage structure that buffers writes in memory and flushes them as sorted runs (SSTables) to disk, with background compaction/merging; lowers random writes at the cost of read/space amplification.</td><td>Used by LevelDB/RocksDB; LSM-based stores like Cassandra and HBase.</td></tr><tr><td>MQ</td><td>Message Queue â durable, asynchronous messaging channel that buffers messages between producers and consumers to decouple services and smooth load.</td><td>RabbitMQ/SQS enqueue events; workers consume from the queue to process jobs off the critical path.</td></tr><tr><td>MVCC</td><td>Multi-Version Concurrency Control â concurrency control that lets readers and writers proceed by keeping multiple row versions and using snapshot visibility rules.</td><td>PostgreSQL snapshot reads; VACUUM removes obsolete versions.</td></tr><tr><td>NoSQL</td><td>Non-relational DBs: documents, key-values, graphs, wide columns.</td><td>MongoDB, Redis, Cassandra.</td></tr><tr><td>OLAP</td><td>Online Analytical Processing â read-heavy analytics.</td><td>BI cubes, columnar stores.</td></tr><tr><td>OLTP</td><td>Online Transaction Processing â write-heavy transactions.</td><td>Order processing systems.</td></tr><tr><td>PK</td><td>Primary Key â unique, non-null identifier for a table row.</td><td><code>users(id UUID PRIMARY KEY)</code>; composite keys across columns.</td></tr><tr><td>RDBMS</td><td>Relational Database Management System â DBMS based on the relational model using tables, rows, and SQL
1with constraints and ACID transactions.</td><td>PostgreSQL, MySQL, SQL Server, Oracle; normalized schemas and joins.</td></tr><tr><td>RDD</td><td>Resilient Distributed Dataset â fault-tolerant distributed collection in Apache Spark enabling parallel transformations across partitions with lineage-based recovery.</td><td>Spark job transforms an RDD with <code>rdd.map()</code>/<code>filter()</code> and caches it via <code>persist()</code> for reuse.</td></tr><tr><td>SQL</td><td>Structured Query Language â query/manage relational DBs.</td><td><code>SELECT * FROM users</code>.</td></tr><tr><td>WAL</td><td>Write-Ahead Logging â durability mechanism that writes log records before data pages.</td><td>PostgreSQL WAL for crash recovery and replication.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>ADO</td><td>ActiveX Data Objects â a legacy Microsoft data access framework for connecting to databases from languages like classic VB and ASP.</td><td><code>ADODB.Connection</code> and <code>Recordset</code> objects for database queries.</td></tr><tr><td>CICS</td><td>Customer Information Control System â IBM mainframe transaction processing monitor that provides high-volume, secure, and reliable online transaction processing.</td><td>Legacy banking and airline systems running CICS transactions.</td></tr><tr><td>CODASYL</td><td>Conference/Committee on Data Systems Languages â consortium behind COBOL and the DBTG network database model that specified schemas, subschemas, and navigation APIs for early DBMS.</td><td>CODASYL DBTG specs defined the network data model adopted by IDS, IDMS, and other mainframe DBMSs.</td></tr><tr><td>DAO</td><td>Data Access Objects â a legacy Microsoft data access API primarily used for accessing Jet (Microsoft Access) databases.</td><td>Predecessor to ADO; used heavily in classic VB applications.</td></tr><tr><td>IDMS</td><td>Integrated Database Management System â commercial network database derived from IDS, providing CODASYL DBTG-compliant data/navigation on IBM mainframes.</td><td>CA-IDMS on IBM z/OS runs core enterprise apps using CODASYL sets and schemas.</td></tr><tr><td>IDS</td><td>Integrated Data Store â Charles Bachmanâs pioneering network database management system for GE mainframes, influencing CODASYL DBTG standards and later products like IDMS.</td><td>Run IDS/II on GE 600/635 systems to model hierarchical/network data; precursor to commercial IDMS releases.</td></tr><tr><td>IMS</td><td>Information Management System â IBM's combined hierarchical database and transaction manager for mainframes, a precursor to relational databases.</td><td>High-performance transaction processing on z/OS; IMS DB/DC.</td></tr><tr><td>OLE DB</td><td>Object Linking and Embedding, Database â a low-level Microsoft API for accessing a wide variety of data sources.</td><td>The underlying interface for ADO; connect to SQL Server via the OLE DB provider.</td></tr><tr><td>RDO</td><td>Remote Data Objects â a legacy Microsoft data access API for remote relational databases, superseded by ADO.</td><td>Early client-server applications in Visual Basic connecting to SQL Server.</td></tr><tr><td>VSAM</td><td>Virtual Storage Access Method â the primary data storage method on IBM z/OS for structured data.</td><td>Key-sequenced datasets (KSDS) used by CICS and batch applications.</td></tr></tbody></table><h2 id="artificial-intelligence" tabindex="-1"><a class="header-anchor" href="#artificial-intelligence"><span>Artificial Intelligence</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AI</td><td>Artificial Intelligence â techniques that enable machines to perform tasks associated with human intelligence (learning, perception, reasoning).</td><td>Use ML/DL models to power AI features like recommendations.</td></tr><tr><td>ANN</td><td>Artificial Neural Network â computational model inspired by biological neurons, used for function approximation and pattern recognition.</td><td>MLPs for tabular data; feedforward nets for classification.</td></tr><tr><td>CNN</td><td>Convolutional Neural Network â neural network architecture specialized for gridâlike data using convolutional filters.</td><td>Image classification/segmentation models.</td></tr><tr><td>CoT</td><td>Chain-of-Thought â prompting technique to elicit step-by-step reasoning.</td><td>"Let's think step by step" to improve math/logic.</td></tr><tr><td>GPT</td><td>Generative Pre-trained Transformer â transformer-based LLM architecture pre-trained on large text corpora and fine-tuned for tasks.</td><td>GPT-4 class models for chat, code, and reasoning.</td></tr><tr><td>LLM</td><td>Large Language Model â NLP model for generation/reasoning.</td><td>GPT/Llama used via APIs or locally.</td></tr><tr><td>MCP</td><td>Model Context Protocol â open protocol to expose tools/data to LLM clients via standardized servers.</td><td>Run an MCP server to provide DB/filesystem tools to an LLM client.</td></tr><tr><td>MoE</td><td>Mixture of Experts â sparse expert routing to scale parameters with near-constant compute.</td><td>Router selects topâk experts per token (Switch-Transformer).</td></tr><tr><td>NER</td><td>Named Entity Recognition â extract and label entities in text.</td><td>Tag PERSON/ORG/LOC from documents.</td></tr><tr><td>NLP</td><td>Natural Language Processing â techniques for understanding and generating human language.</td><td>Text classification, NER, summarization, translation.</td></tr><tr><td>OCR</td><td>Optical Character Recognition â convert images/scans of text into machineâencoded text using computer vision and sequence models.</td><td>Tesseract or deepâlearning OCR to extract text from documents/receipts.</td></tr><tr><td>RAG</td><td>Retrieval-Augmented Generation â ground model outputs by retrieving external knowledge at query time.</td><td>Retrieve topâk docs from a vector store and include them in the prompt.</td></tr><tr><td>RL</td><td>Reinforcement Learning â learning by interaction with an environment via rewards.</td><td>Qâlearning, policy gradients; RLHF for model alignment.</td></tr><tr><td>RLHF</td><td>Reinforcement Learning from Human Feedback â align models using human preference signals via a learned reward model.</td><td>Collect preference pairs, train a reward model, then fineâtune with PPO.</td></tr><tr><td>RNN</td><td>Recurrent Neural Network â sequence model with recurrent connections.</td><td>LSTM/GRU for language modeling and time series.</td></tr><tr><td>SFT</td><td>Supervised Fine-Tuning â fineâtune a pretrained model on labeled inputâoutput pairs to specialize behavior.</td><td>Fineâtune a base LLM on instruction datasets before RLHF.</td></tr><tr><td>TTS</td><td>Text-to-Speech â synthesize speech audio from text.</td><td>Generate spoken responses from a chatbot.</td></tr><tr><td>VLM</td><td>Vision-Language Model â jointly processes images and text.</td><td>CLIP, BLIP, LLaVA for captioning and VQA.</td></tr></tbody></table><h2 id="reliability-operations" tabindex="-1"><a class="header-anchor" href="#reliability-operations"><span>Reliability & Operations</span></a></h2><table><thead><tr><th>
1Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>DR</td><td>Disaster Recovery â restore service after catastrophic failure.</td><td>DR runbooks; backup restore drills.</td></tr><tr><td>HA</td><td>High Availability â design to minimize downtime.</td><td>Multi-zone deployment with failover.</td></tr><tr><td>MTTR</td><td>Mean Time To Repair/Recover â restore time after failure.</td><td>Track MTTR per incident.</td></tr><tr><td>RCA</td><td>Root Cause Analysis â identify underlying cause.</td><td>Postmortem documents.</td></tr><tr><td>RPO</td><td>Recovery Point Objective â max acceptable data loss.</td><td>5-minute RPO via frequent backups.</td></tr><tr><td>RTO</td><td>Recovery Time Objective â target restore time.</td><td>30-minute RTO for tier-1 services.</td></tr><tr><td>SLA</td><td>Service Level Agreement â contractual target.</td><td>99.9% monthly uptime.</td></tr><tr><td>SLI</td><td>Service Level Indicator â measured metric.</td><td>Request success rate, p95 latency.</td></tr><tr><td>SLO</td><td>Service Level Objective â internal target.</td><td>99.95% quarterly availability.</td></tr><tr><td>SPOF</td><td>Single Point Of Failure â outage if it fails.</td><td>Single DB primary without replica.</td></tr><tr><td>SRE</td><td>Site Reliability Engineering â SWE meets ops.</td><td>Error budgets, toil reduction.</td></tr></tbody></table><h2 id="performance-metrics" tabindex="-1"><a class="header-anchor" href="#performance-metrics"><span>Performance & Metrics</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>Apdex</td><td>Application Performance Index â satisfaction score based on latency thresholds.</td><td>Apdex ⥠0.9 target.</td></tr><tr><td>APM</td><td>Application Performance Monitoring â traces/metrics/errors for apps.</td><td>Distributed tracing spans across services.</td></tr><tr><td>CLS</td><td>Cumulative Layout Shift â visual stability (Web Vitals).</td><td>CLS < 0.1.</td></tr><tr><td>FLOPS</td><td>Floating-Point Operations Per Second â measure of compute performance for CPUs/GPUs/accelerators.</td><td>GPU rated at 30 TFLOPS; benchmark sustained vs peak GFLOPS.</td></tr><tr><td>FPS</td><td>Frames Per Second â render/update frequency for graphics/video; higher is smoother within latency/refresh constraints.</td><td>Games target 60+ FPS; VR aims for 90â120 FPS.</td></tr><tr><td>INP</td><td>Interaction to Next Paint â user input responsiveness (Web Vitals).</td><td>INP < 200 ms.</td></tr><tr><td>IOPS</td><td>Input/Output Operations Per Second â storage throughput measurement.</td><td>NVMe SSD sustaining 500k+ random read IOPS.</td></tr><tr><td>IPC</td><td>Instructions Per Clock/Cycle â measure of a CPU's architectural efficiency, independent of clock speed.</td><td>A CPU with higher IPC can be faster than one with a higher clock rate.</td></tr><tr><td>LCP</td><td>Largest Contentful Paint â main content render time (Web Vitals).</td><td>LCP < 2.5 s.</td></tr><tr><td>LoC</td><td>Lines of Code â simple size metric counting source lines; can indicate scope but is a poor proxy for complexity or value.</td><td>Compare module sizes; avoid using LoC alone for productivity.</td></tr><tr><td>MIPS</td><td>Million Instructions Per Second â rough measure of integer instruction throughput; varies widely by ISA and instruction complexity.</td><td>Historical CPU comparisons; not comparable across architectures/workloads.</td></tr><tr><td>P50/P95/P99</td><td>Latency percentiles â response time distribution.</td><td>P95 latency under 250 ms.</td></tr><tr><td>RPS/QPS</td><td>Requests/Queries Per Second â service throughput.</td><td>API serves 2k RPS at peak.</td></tr><tr><td>RUM</td><td>Real User Monitoring â measurements from real users.</td><td>In-browser beacons for Web Vitals.</td></tr><tr><td>TPS</td><td>Transactions Per Second â business-level throughput.</td><td>Payments at 150 TPS during sale.</td></tr><tr><td>TTFB</td><td>Time To First Byte â time to first response byte.</td><td>Aim for TTFB < 200 ms.</td></tr><tr><td>TTI</td><td>Time To Interactive â page becomes reliably usable.</td><td>TTI ~ 3.0 s.</td></tr></tbody></table><h2 id="networking-protocols" tabindex="-1"><a class="header-anchor" href="#networking-protocols"><span>Networking & Protocols</span></a></h2><table><thead><tr><th>
1Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AMQP</td><td>Advanced Message Queuing Protocol â open standard for asynchronous messaging between applications, enabling reliable, interoperable, and feature-rich communication.</td><td>RabbitMQ/ActiveMQ brokers implementing AMQP 0-9-1 or 1.0 for queuing and routing.</td></tr><tr><td>ARP</td><td>Address Resolution Protocol â map IP addresses to MAC addresses on a LAN.</td><td>ARP cache; gratuitous ARP.</td></tr><tr><td>AS</td><td>Autonomous System â a collection of IP networks under a single administrative control, identified by an ASN and used in BGP routing.</td><td>An ISP, a university, or a large tech company's network.</td></tr><tr><td>ASN</td><td>Autonomous System Number â a globally unique identifier for a network, used in BGP routing.</td><td>ISP route announcements include their ASN; <code>AS15169</code> is Google's ASN.</td></tr><tr><td>BGP</td><td>Border Gateway Protocol â inter-domain routing protocol of the internet.</td><td>ISP peering and route advertisements.</td></tr><tr><td>BIND</td><td>Berkeley Internet Name Domain â a widely used, open-source DNS server.</td><td>Configure zones in <code>named.conf</code>; query a BIND server with <code>dig</code>.</td></tr><tr><td>BPF</td><td>Berkeley Packet Filter â kernel-level virtual machine for packet filtering/observability (eBPF on modern kernels).</td><td>Capture packets with tcpdump; eBPF programs for tracing.</td></tr><tr><td>CIDR</td><td>Classless Inter-Domain Routing â notation for IP prefixes and aggregation.</td><td><code>10.0.0.0/16</code> VPC; subnetting <code>/24</code>; route summarization.</td></tr><tr><td>CNAME</td><td>Canonical Name â DNS record that aliases one hostname to another.</td><td><code>www</code> CNAME to <code>example.com</code>; avoid at zone apex without ALIAS/ANAME.</td></tr><tr><td>CLNP</td><td>Connectionless Network Protocol â OSI layer 3 datagram protocol (ISO/IEC 8473) that provides connectionless packet delivery using NSAP addressing within OSI stacks.</td><td>DECnet/OSI and X.25 backbones carried CLNP traffic with IS-IS routing NSAP-addressed packets between hosts.</td></tr><tr><td>NSAP</td><td>Network Service Access Point â OSI network-layer address format carrying AFI/IDI and DSP fields used by CLNP/IS-IS instead of IP addresses.</td><td>An OSI host might use NSAP <code>49.0001.1921.6800.1001.00</code> with IS-IS routing NSAP prefixes across an OSI backbone.</td></tr><tr><td>CR-LDP</td><td>Constraint-Based Routed Label Distribution Protocol â MPLS TE signaling that extends LDP with constraint advertisement and explicit route objects to set up engineered LSPs without RSVP.</td><td>Some carriers historically deployed CR-LDP to establish bandwidth-guaranteed LSPs before migrating to RSVP-TE.</td></tr><tr><td>CRC</td><td>Cyclic Redundancy Check â an error-detecting code used to detect accidental changes to digital data.</td><td>Ethernet frame check sequence (FCS); CRC-32 in ZIP/PNG files.</td></tr><tr><td>DHCP</td><td>Dynamic Host Configuration Protocol â automatic IP configuration.</td><td>DHCP assigns IP/gateway/DNS.</td></tr><tr><td>DHT</td><td>Distributed Hash Table â decentralized key-value store that partitions data across a peer-to-peer network, enabling scalable lookups without a central server.</td><td>BitTorrent Mainline DHT for peer discovery; IPFS for content addressing.</td></tr><tr><td>DoH</td><td>DNS over HTTPS â perform DNS resolution over HTTPS for privacy/integrity.</td><td><code>https://dns.google/dns-query</code> DoH endpoint.</td></tr><tr><td>DWDM</td><td>Dense Wavelength Division Multiplexing â optical multiplexing technique that carries many tightly spaced light wavelengths on a single fiber pair to massively increase backbone capacity.</td><td>Telco long-haul links stack 100G/400G channels with DWDM mux/demux gear and optical amplifiers.</td></tr><tr><td>FC</td><td>Fibre Channel â highâspeed serial transport for storage networking (SANs) with switched fabrics, typically 8/16/32 Gbit/s, carrying SCSI/FCP.</td><td>Connect hosts to SAN arrays over FC via HBAs and switches; zoning and LUN masking.</td></tr><tr><td>FDDI</td><td>Fiber Distributed Data Interface â ANSI token-ring LAN standard operating at 100 Mbit/s over dual counter-rotating fiber rings with timed token passing and built-in redundancy; once popular for campus backbones before Fast/Gigabit Ethernet.</td><td>Interconnect building LANs via FDDI dual rings, with automatic wrap-around on fiber breaks to maintain service.</td></tr><tr><td>HDLC</td><td>High-Level Data Link Control â ISO bit-oriented layer 2 protocol using frame flag delimiters, bit stuffing, and sliding-window ARQ; foundation for derivatives like SDLC, LAPB, PPP, and Frame Relay.</td><td>Serial WAN links encapsulating packets in HDLC frames; routers using Cisco HDLC or LAPD signaling over ISDN.</td></tr><tr><td>HTTP</td><td>Hypertext Transfer Protocol â web application protocol.</td><td><code>GET /index.html</code> over TCP.</td></tr><tr><td>HTTPS</td><td>HTTP over TLS â encrypted HTTP.</td><td>Padlock in browsers.</td></tr><tr><td>ICMP</td><td>Internet Control Message Protocol â diagnostics/control.</td><td><code>ping</code>
1 uses Echo Request/Reply.</td></tr><tr><td>IMAP</td><td>Internet Message Access Protocol â email retrieval/sync.</td><td>Mail clients syncing mailboxes.</td></tr><tr><td>IP</td><td>Internet Protocol â addressing/routing (IPv4/IPv6).</td><td>Packet delivery across networks.</td></tr><tr><td>IPsec</td><td>Internet Protocol Security â suite of protocols for authenticating and encrypting IP packets at the network layer (AH/ESP) with key exchange via IKE.</td><td>Site-to-site or remote-access VPNs using IKEv2 with ESP in tunnel mode; transport mode for host-to-host.</td></tr><tr><td>iSCSI</td><td>Internet Small Computer Systems Interface â block storage protocol that encapsulates SCSI commands over TCP/IP.</td><td>Connect initiators to targets on port 3260; boot from SAN; map LUNs over the network.</td></tr><tr><td>ISP</td><td>Internet Service Provider â company that provides internet connectivity and related services.</td><td>Residential broadband, business fiber links, and transit.</td></tr><tr><td>L2TP</td><td>Layer 2 Tunneling Protocol â encapsulates PPP frames to create tunnels across IP networks, typically paired with IPsec for encryption/authentication.</td><td>Remote-access VPN uses L2TP over IPsec (UDP 1701/500/4500) to tunnel client traffic through a secure gateway.</td></tr><tr><td>LAN</td><td>Local Area Network â network covering a limited geographic area such as a home, office, or campus.</td><td>Ethernet/WiâFi LAN with switches and access points.</td></tr><tr><td>LDAP</td><td>Lightweight Directory Access Protocol â protocol for accessing and managing directory services.</td><td>Authenticate/lookup users and groups in an LDAP directory.</td></tr><tr><td>LDP</td><td>Label Distribution Protocol â MPLS control plane that advertises label bindings between neighbors to build label-switched paths based on IGP routes without explicit traffic engineering.</td><td>ISPs run LDP over their IGP so MPLS L3VPNs follow OSPF/IS-IS shortest paths by default.</td></tr><tr><td>LSP</td><td>Label-Switched Path â the unidirectional MPLS forwarding path created by label bindings that steer packets hop by hop through an MPLS network.</td><td>Traffic for a VPN flows along an LSP signaled by LDP or RSVP-TE from ingress PE to egress PE.</td></tr><tr><td>MAC</td><td>Media Access Control â data-link sublayer that governs medium access, framing, and addressing on LANs.</td><td>Ethernet MAC handles frame delimiting, MAC addressing, and channel access.</td></tr><tr><td>MPLS</td><td>Multiprotocol Label Switching â high-performance packet forwarding that uses short labels to make traffic-engineered L2.5 paths across provider cores.</td><td>ISP backbone uses MPLS L3VPNs/TE to steer customer traffic and provide QoS across the WAN.</td></tr><tr><td>MPLS-TE</td><td>MPLS Traffic Engineering â extensions that compute constraint-based LSPs using RSVP-TE/CR-LDP to steer traffic along engineered paths that meet bandwidth, affinity, and protection requirements.</td><td>Carriers pin backup-capable label-switched paths around congested links using RSVP-TE with fast reroute.</td></tr><tr><td>MQTT</td><td>Message Queuing Telemetry Transport â lightweight publish-subscribe protocol for constrained devices and low-bandwidth, high-latency networks; widely used in IoT.</td><td>IoT sensors publishing telemetry to an MQTT broker; mobile push notifications.</td></tr><tr><td>MTU</td><td>Maximum Transmission Unit â largest payload size (in bytes) that can be sent in a single layerâ2 frame without fragmentation.</td><td>Ethernet MTU 1500; jumbo frames MTU 9000; Path MTU Discovery avoids fragmentation.</td></tr><tr><td>MX</td><td>Mail Exchanger â DNS record that specifies the mail servers responsible for accepting email for a domain, with preferences for priority/failover.</td><td><code>example.com. MX 10 mail1.example.com.</code> and <code>MX 20 mail2.example.com.</code> as backup.</td></tr><tr><td>NAT</td><td>Network Address Translation â remap private to public addresses.</td><td>Home routers performing PAT.</td></tr><tr><td>NFS</td><td>Network File System â distributed file system protocol for sharing files over a network.</td><td>Mount remote directories via NFSv3/NFSv4.</td></tr><tr><td>NS</td><td>Name Server â DNS server authoritative for a zone; also the DNS record type that delegates to authoritative servers.</td><td><code>NS</code> records pointing to <code>ns1.example.com</code> for a domain.</td></tr><tr><td>NTP</td><td>Network Time Protocol â synchronize clocks over networks using a hierarchy of time sources.</td><td><code>chrony</code>/<code>ntpd</code> syncing to NTP servers (stratum levels).</td></tr><tr><td>OSI</td><td>
1Open Systems Interconnection â conceptual sevenâlayer networking reference model for describing protocols and interoperability (Layers 1â7: PhysicalâApplication).</td><td>Map protocols to layers (e.g., Ethernet=L2, IP=L3, TCP=L4, HTTP=L7); teaching/troubleshooting taxonomy.</td></tr><tr><td>OSPF</td><td>Open Shortest Path First â interior gateway routing protocol.</td><td>Multi-area OSPF in enterprises.</td></tr><tr><td>OTN</td><td>Optical Transport Network â ITU-T G.709 digital wrapper standard that multiplexes client signals into optical channels with forward error correction and management for carrier backbones.</td><td>Carriers groom Ethernet/SONET traffic into ODUk containers and transport them over OTU4 wavelengths with OTN switches.</td></tr><tr><td>P2P</td><td>Peer-to-Peer â decentralized communication model where nodes act as both clients and servers without a central coordinator.</td><td>BitTorrent swarms; WebRTC data channels; DHT-based peer discovery.</td></tr><tr><td>PoE</td><td>Power over Ethernet â standard for providing electrical power through Ethernet cables to devices like IP cameras, VoIP phones, and wireless access points.</td><td>802.3af/at/bt standards for PoE/PoE+/PoE++.</td></tr><tr><td>QoS</td><td>Quality of Service â mechanisms that classify and prioritize traffic to meet latency, jitter, and loss requirements.</td><td>Configure DiffServ/DSCP queues on routers to give voice and video higher priority than bulk data.</td></tr><tr><td>QUIC</td><td>Quick UDP Internet Connections â encrypted, multiplexed transport over UDP.</td><td>HTTP/3 runs over QUIC.</td></tr><tr><td>RDP</td><td>Remote Desktop Protocol â a proprietary protocol from Microsoft for remote access to a graphical user interface on a Windows machine.</td><td>Connect to a Windows server with an RDP client; <code>mstsc.exe</code>.</td></tr><tr><td>RSVP-TE</td><td>Resource Reservation Protocol - Traffic Engineering â MPLS control-plane signaling that establishes label-switched paths with bandwidth reservations using RSVP extensions for constraints, fast reroute, and preemption.</td><td>Configure RSVP-TE tunnels between provider edge routers to reserve 10 Gbit/s paths with explicit hop lists and standby LSPs.</td></tr><tr><td>SDH</td><td>Synchronous Digital Hierarchy â ITU-T optical transport standard harmonizing SONET internationally with STM/STM-N rates, VC containers, and automatic protection switching for carrier backbones.</td><td>European telcos running STM-16/STM-64 rings that interop with SONET via gateways; metro networks reroute around fiber faults in <50 ms.</td></tr><tr><td>SFTP</td><td>SSH File Transfer Protocol â file transfer over SSH.</td><td><code>sftp user@host</code> uploads/downloads.</td></tr><tr><td>SMB</td><td>Server Message Block â network file/printer sharing protocol used mainly by Windows; modern versions (SMBv2/v3) support signing/encryption.</td><td>Mount <code>\\\\server\\share</code>; Samba on Unix; avoid SMBv1 due to security issues.</td></tr><tr><td>SMTP</td><td>Simple Mail Transfer Protocol â send email.</td><td>MTA relaying messages.</td></tr><tr><td>SNMP</td><td>Simple Network Management Protocol â protocol for monitoring and managing networked devices via a hierarchical MIB of OIDs, supporting polling and asynchronous traps/informs.</td><td>Poll interfaces/CPU via GET/GETNEXT/GETBULK; receive traps; v1/v2c (community) and v3 (auth/privacy).</td></tr><tr><td>SONET</td><td>Synchronous Optical Network â ANSI fiber transport standard using time-division multiplexed frames (STS/OC rates) with built-in protection switching; interoperable internationally via ITU-T SDH.</td><td>Telco backbones delivering OC-3/OC-12/OC-192 rings for voice/data; metro rings that auto-switch on fiber cuts.</td></tr><tr><td>SR-MPLS</td><td>Segment Routing over MPLS â control plane that encodes segment routing label stacks in MPLS to replace LDP/RSVP, enabling source-routed paths, traffic engineering, and fast reroute with simplified signaling.</td><td>Deploy SR-MPLS in a service provider core so ingress routers push segment lists to steer L3VPN traffic without RSVP-TE.</td></tr><tr><td>SRv6</td><td>Segment Routing over IPv6 â segment routing data plane that encodes instruction lists in IPv6 Segment Routing Headers (SRH), enabling source-routed paths, service chaining, and traffic engineering without MPLS labels.</td><td>Use SRv6 in a SP core so packets carry SID lists (<code>2001:db8::A</code>, <code>::B</code>) to steer flows through specific functions or nodes; integrate with SRv6 TE and network programming.</td></tr><tr><td>SSE</td><td>Server-Sent Events â HTTP-based serverâclient stream.</td><td><code>EventSource('/events')</code>.</td></tr><tr><td>STP</td><td>Spanning Tree Protocol â network protocol that ensures a loop-free topology for bridged Ethernet networks.</td><td>Switches running STP/RSTP to prevent broadcast storms.</td></tr><tr><td>TCP</td><td>Transmission Control Protocol â reliable byte stream.</td><td>HTTP, TLS use TCP.</td></tr><tr><td>TCP/IP</td><td>Transmission Control Protocol / Internet Protocol â foundational internet protocol suite encompassing transport, network, and related layers.</td><td>Classic network stack model; "TCP/IP networking" on UNIX systems.</td></tr><tr><td>TLD</td><td>Top-Level Domain â the highest level in the DNS hierarchy, forming the rightmost label of a domain name.</td><td><code>.com</code>, <code>.org</code>, country-code TLDs like <code>.uk</code>; ICANN-managed root zone.</td></tr><tr><td>TTL</td><td>
1Time To Live â lifetime for packets/cached records.</td><td>DNS TTL controls cache duration.</td></tr><tr><td>UDP</td><td>User Datagram Protocol â connectionless, low-latency.</td><td>DNS, streaming.</td></tr><tr><td>UNC</td><td>Universal Naming Convention â Windows network path notation for accessing resources by server/share.</td><td><code>\\\\\\\\server\\\\share\\\\folder\\\\file.txt</code>; used with SMB.</td></tr><tr><td>VLAN</td><td>Virtual Local Area Network â Layer 2 network segmentation on a switch, isolating broadcast domains; tagging via IEEE 802.1Q.</td><td>VLAN 10/20 on access/trunk ports; tagged vs untagged frames.</td></tr><tr><td>WAN</td><td>Wide Area Network â network spanning large geographic areas interconnecting LANs over provider links or the public internet.</td><td>MPLS links, SDâWAN, siteâtoâsite VPN between offices.</td></tr><tr><td>WebRTC</td><td>Web Real-Time Communication â a framework providing browsers and mobile applications with real-time communication (RTC) capabilities via simple APIs.</td><td>Peer-to-peer video conferencing, screen sharing, and data channels in the browser.</td></tr><tr><td>WHOIS</td><td>WHOIS protocol â query/response protocol for retrieving registration information about internet resources such as domain names and IP address allocations.</td><td><code>whois example.com</code> to get registrar/registrant data; RDAP is the modern HTTP-based successor.</td></tr><tr><td>WS</td><td>WebSocket â full-duplex over single TCP connection.</td><td><code>ws://example.com/socket</code>.</td></tr><tr><td>WSS</td><td>WebSocket Secure â WebSocket over TLS.</td><td><code>wss://example.com/socket</code>.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>ADSL</td><td>Asymmetric Digital Subscriber Line â a common type of DSL where download speeds are faster than upload speeds.</td><td>
1Consumer broadband over telephone lines.</td></tr><tr><td>CSU</td><td>Channel Service Unit â legacy telco/customer-premises device that terminates a digital leased circuit, provides line conditioning/loopback diagnostics, and hands off a clean interface to a paired DSU or router.</td><td>Standalone CSU on a T1 line or integrated CSU/DSU modules in enterprise routers delivering telco-managed point-to-point links.</td></tr><tr><td>DCE</td><td>Data Circuit-terminating Equipment â provides clocking, signal conversion, and circuit termination for serial/WAN links so attached DTEs can communicate.</td><td>CSU/DSU, cable/DSL modems, and telco demarc gear act as the DCE in leased-line setups.</td></tr><tr><td>DSL</td><td>Digital Subscriber Line â a family of technologies for transmitting digital data over telephone lines.</td><td>ADSL, SDSL, VDSL are all types of DSL.</td></tr><tr><td>DSU</td><td>Data Service Unit â legacy digital modem that converts the CSU-provided line signal into synchronous serial presented to DTE gear, completing the CSU/DSU pair on leased circuits.</td><td>External DSUs or router interface cards carrying T1/E1 circuits expose V.35/RS-449 ports for routers/terminals.</td></tr><tr><td>DTE</td><td>Data Terminal Equipment â end device that connects to a DCE to originate or receive data on a serial/WAN circuit, typically providing clocking recovery from the DCE.</td><td>Routers, terminals, or customer-edge gear plugging into a CSU/DSU; use <code>show controllers serial</code> to verify DTE/DCE role via cable pinout.</td></tr><tr><td>FTP</td><td>File Transfer Protocol â legacy, unencrypted by default.</td><td><code>ftp</code> client for file transfers.</td></tr><tr><td>FTPS</td><td>FTP over TLS â encrypted FTP.</td><td>Implicit/explicit FTPS modes.</td></tr><tr><td>iPXE</td><td>Open-source network boot firmware/bootloader extending PXE with HTTP(S), iSCSI, FCoE, AoE, scripts, and TLS.</td><td>Chainload iPXE via PXE; fetch an HTTPS boot script to load kernel/initrd.</td></tr><tr><td>IRC</td><td>Internet Relay Chat â real-time text messaging protocol and networks for group channels and direct messages.</td><td>Join #project on Libera Chat using irssi or WeeChat.</td></tr><tr><td>NBT</td><td>NetBIOS over TCP/IP â transport that carries NetBIOS name, datagram, and session traffic over TCP/UDP (ports 137â139) so legacy NetBIOS applications work on IP networks.</td><td>Keep NBT only for backward compatibility with old Windows clients/printers; disable when moving fully to DNS/SMB over TCP 445.</td></tr><tr><td>NetBEUI</td><td>NetBIOS Extended User Interface â non-routable, broadcast-heavy transport protocol for NetBIOS communications on small LANs; superseded by NBT/TCP/IP.</td><td>Early Windows peer-to-peer networking used NetBEUI; administrators removed it when migrating to TCP/IP-based SMB.</td></tr><tr><td>NetBIOS</td><td>Network Basic Input/Output System â legacy API and naming services that provided session/datagram communication atop early LAN transports (NetBEUI, IPX/SPX, later NBT).</td><td>DOS/Windows for Workgroups apps used NetBIOS names for SMB file/print sharing; modern AD domains phase out NetBIOS names in favor of DNS.</td></tr><tr><td>NIS</td><td>Network Information Service â a legacy Unix directory service for distributing system configuration data like user and host names between computers on a network.</td><td>Originally known as Yellow Pages (YP); superseded by LDAP.</td></tr><tr><td>NNTP</td><td>Network News Transfer Protocol â application protocol for distributing, querying, and posting Usenet articles over TCP.</td><td>Connect to Usenet servers on 119 (or 563 for NNTPS) to read/post news.</td></tr><tr><td>POP3</td><td>Post Office Protocol v3 â simple email retrieval.</td><td>Fetch-and-delete mailbox flow.</td></tr><tr><td>PPP</td><td>Point-to-Point Protocol â data link layer protocol for encapsulating network traffic over serial links; supports authentication, compression, and multilink.</td><td>Dial-up links; PPPoE for broadband; CHAP/PAP authentication.</td></tr><tr><td>PPTP</td><td>Point-to-Point Tunneling Protocol â legacy VPN tunneling protocol that encapsulates PPP over GRE with MPPE encryption; considered insecure and deprecated.</td><td>Historical Windows VPNs using PPTP; replace with IPsec/OpenVPN/WireGuard/L2TP over IPsec.</td></tr><tr><td>PXE</td><td>Preboot Execution Environment â standard for network booting clients using DHCP/BOOTP to obtain boot info and TFTP/HTTP to fetch boot loaders/images.</td><td>PXE boot a workstation from a provisioning server into an installer.</td></tr><tr><td>RIP</td><td>Routing Information Protocol â distance-vector interior gateway protocol using hop count as its metric with periodic full-table updates.</td><td>RIP v2 on small LANs; max 15 hops; split horizon/poison reverse to mitigate loops.</td></tr><tr><td>RLOGIN</td><td>Remote Login â BSD plaintext remote login protocol; superseded by SSH.</td><td><code>rlogin host</code> for interactive sessions on legacy UNIX systems.</td></tr><tr><td>RSH</td><td>Remote Shell â BSD plaintext remote command execution; superseded by SSH.</td><td><code>rsh host command</code> on legacy UNIX; avoid due to lack of security.</td></tr><tr><td>TFTP</td><td>Trivial File Transfer Protocol â simple UDP-based file transfer protocol commonly used for network boot and configuration.</td><td>PXE firmware downloads boot images via TFTP; no auth/encryption.</td></tr><tr><td>UPnP</td><td>Universal Plug and Play â discovery and control protocols for devices/services on a local network; includes IGD for NAT port mappings.</td><td>Home routers autoâopen ports via UPnP IGD; device discovery/control on LANs.</td></tr><tr><td>VDSL</td><td>Very-high-bit-rate Digital Subscriber Line â a faster version of DSL, often used for fiber-to-the-curb deployments.</td><td>Higher speeds over shorter distances than ADSL.</td></tr><tr><td>WINS</td><td>Windows Internet Name Service â Microsoft's legacy database-backed NetBIOS name resolution service that replicates between servers and integrates with DHCP for old Windows clients.</td><td>Maintain WINS servers in mixed Active Directory environments; DHCP option 44/46 hands out WINS server IPs to legacy nodes.</td></tr><tr><td>XMPP</td><td>Extensible Messaging and Presence Protocol â open, federated XML-based protocol for instant messaging and presence.</td><td>Jabber, Google Talk (legacy); used in federated chat and IoT.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>AIM</td><td>AOL Instant Messenger â a pioneering instant messaging service from AOL, popular in the late 1990s and 2000s.</td><td>Buddy Lists, away messages, and chat sounds.</td></tr><tr><td>ARPANET</td><td>Advanced Research Projects Agency Network â pioneering packetâswitched network and direct precursor to the modern Internet.</td><td>1969 UCLAâSRI link; IMPs; 1983 cutover from NCP to TCP/IP.</td></tr><tr><td>ATM</td><td>Asynchronous Transfer Mode â a telecommunications standard for cell-based switching, designed for high-speed voice, video, and data.</td><td>Used in telco backbones and for DSL; superseded by IP-based networks.</td></tr><tr><td>BBS</td><td>
1Bulletin Board System â preâweb dialâup systems.</td><td>Modem dialâins for forums/files before the web.</td></tr><tr><td>BITNET</td><td>Because Itâs Time Network â early academic store-and-forward network linking universities via leased lines using IBMâs RSCS protocol; provided email, file transfer, and LISTSERV mailing lists.</td><td>Colleges connected mainframes to BITNET in the 1980s; LISTSERV communities flourished before widespread internet access.</td></tr><tr><td>USENET</td><td>User Network â decentralized, distributed discussion system operating via the UUCP and later NNTP protocols, enabling newsgroups and threaded conversations across servers worldwide.</td><td>1980s/1990s communities exchanged posts in <code>comp.*</code>, <code>sci.*</code>, <code>alt.*</code> newsgroups replicated between sites; content accessible via NNTP readers.</td></tr><tr><td>BOOTP</td><td>Bootstrap Protocol â assigns IP configuration to diskless clients at boot, predecessor to DHCP.</td><td>Network boot ROM requests IP/gateway/TFTP server; largely replaced by DHCP.</td></tr><tr><td>CSMA/CD</td><td>Carrier-Sense Multiple Access with Collision Detection â media access control method used by early Ethernet on a shared bus.</td><td>Half-duplex hubs; nodes listen before transmitting and detect collisions.</td></tr><tr><td>CSNET</td><td>Computer Science Network â an early computer network that provided services to university computer science departments, funded by the NSF.</td><td>A key stepping stone between ARPANET and the modern internet.</td></tr><tr><td>CYCLADES</td><td>French research packet-switching network (CYCLADES project) that pioneered datagrams, host responsibility for reliability, and end-to-end design principles that influenced TCP/IP.</td><td>1970s French R&D network connecting CYCLADES hosts via CIGALE routers; experience informed the Internet's datagram model.</td></tr><tr><td>DECnet</td><td>Digital Equipment Corporation's proprietary network protocol suite for DEC systems; largely superseded by TCP/IP.</td><td>VAX/VMS clusters and DEC systems communicating over DECnet Phase IV/V.</td></tr><tr><td>ICQ</td><td>"I Seek You" â one of the first internet-wide instant messaging services.</td><td>User identification numbers (UINs) and the "uh-oh!" sound.</td></tr><tr><td>JANET</td><td>Joint Academic Network â the UKâs national research and education network providing high-speed connectivity and services for universities, colleges, and research institutions.</td><td>JANET interconnects UK campuses, data centers, and global research networks via the backbone operated by Jisc.</td></tr><tr><td>IPX</td><td>Internetwork Packet Exchange â Novell's network-layer protocol used with SPX and NetWare; replaced by IP in modern networks.</td><td>Legacy NetWare LANs using IPX addressing and routing.</td></tr><tr><td>ISDN</td><td>Integrated Services Digital Network â circuitâswitched digital telephony offering voice and data over PSTN with separate bearer/signaling channels.</td><td>BRI (2B+D) for small sites; PRI (23B+D NA / 30B+D EU) for trunks.</td></tr><tr><td>MILNET</td><td>Military Network â the DoD-operated segment of the ARPANET split off in 1983 to carry unclassified military traffic while academic research continued on the remaining ARPANET.</td><td>MILNET backbone connected defense sites and gateways, later evolving into the Defense Data Network and precursors to NIPRNet.</td></tr><tr><td>MSN</td><td>The Microsoft Network â an early online service and ISP from Microsoft, later known for its web portal and instant messenger.</td><td>MSN Messenger was a major competitor to AIM and ICQ.</td></tr><tr><td>NCP</td><td>NetWare Core Protocol â Novell NetWare file/print service protocol suite running over IPX/SPX (later IP).</td><td>Legacy NetWare clients mapping drives/printers via NCP.</td></tr><tr><td>NCP</td><td>Network Control Program â early ARPANET host protocol providing a transport layer and flow control prior to the adoption of TCP/IP.</td><td>Used until the 1983 flag day cutover to TCP/IP; sockets over NCP.</td></tr><tr><td>NDS</td><td>Novell Directory Services â directory service for managing identities, resources, and access in Novell NetWare environments (later evolved into eDirectory).</td><td>Centralized users/groups/policies across NetWare; replaced/renamed as eDirectory.</td></tr><tr><td>NSFNET</td><td>National Science Foundation Network â U.S. government-funded backbone that expanded academic access to the ARPANET successor, catalyzing the transition to todayâs commercial internet before its 1995 decommissioning.</td><td>Regional networks connected to NSFNET T1/T3 backbones; commercial ISPs emerged as NSFNET traffic opened to broader use.</td></tr><tr><td>PAD</td><td>Packet Assembler/Disassembler â X.25-era device that buffered character-stream or async terminal traffic and converted it to packets for a public data network (and vice versa).</td><td>Retail POS terminals or green-screen async devices connected through a PAD to reach hosts over public X.25 services.</td></tr><tr><td>PUP</td><td>PARC Universal Packet â early internetworking protocol suite developed at Xerox PARC that influenced XNS and later networking concepts.</td><td>
1Historical LAN internetworking; precursor to concepts adopted in later stacks.</td></tr><tr><td>RARP</td><td>Reverse Address Resolution Protocol â legacy protocol for discovering an IP address given a MAC address.</td><td>Early diskless boot; superseded by BOOTP/DHCP.</td></tr><tr><td>SDLC</td><td>Synchronous Data Link Control â IBM's bit-oriented data link layer protocol for SNA networks, using poll/select over multi-drop lines; superseded by HDLC-derived standards and TCP/IP transports.</td><td>Host mainframes controlling remote 3270/3780 cluster controllers across leased lines via SDLC.</td></tr><tr><td>SLIP</td><td>Serial Line Internet Protocol â simple encapsulation of IP over serial links; lacks features like authentication, negotiation, and error detection.</td><td>Early dial-up IP connectivity; superseded by PPP.</td></tr><tr><td>SNA</td><td>Systems Network Architecture â IBM's proprietary networking architecture for mainframes and enterprise networks; largely superseded by TCP/IP.</td><td>IBM 3270/5250 terminals and LU types; later SNA over IP via Enterprise Extender.</td></tr><tr><td>SPX</td><td>Sequenced Packet Exchange â Novell's transport-layer protocol running over IPX, analogous to TCP; superseded by TCP/IP.</td><td>NetWare clients/servers using IPX/SPX for file/print services.</td></tr><tr><td>UUCP</td><td>Unix-to-Unix Copy Protocol â store-and-forward system for transferring files, email, and netnews over dial-up/serial links; pre-internet era networking.</td><td>Early email/news via bang paths (uucp!host!user); largely replaced by SMTP/NNTP over IP.</td></tr><tr><td>UUNET</td><td>Unix-to-Unix Network â one of the first commercial internet service providers, evolving from a Usenet feed service into a major backbone operator that helped commercialize internet access.</td><td>Provided UUCP/Usenet feeds, then IP transit and dial-up services before mergers into MCI/WorldCom.</td></tr><tr><td>WAIS</td><td>Wide Area Information Servers â early distributed document indexing/search and retrieval system predating modern web search; used client/server over Z39.50.</td><td>1990s internet search across WAIS servers before mainstream web engines.</td></tr><tr><td>X.25</td><td>ITU-T legacy packet-switched WAN protocol using virtual circuits over carrier networks; superseded by Frame Relay/ATM/IP.</td><td>Early bank/pos/leased-line links using X.25 PADs and PVC/SVC connections.</td></tr><tr><td>XNS</td><td>Xerox Network Systems â Xerox's network protocol suite from PARC that influenced later protocols (e.g., IPX/SPX, AppleTalk).</td><td>Historical LAN stack alongside SNA/DECnet; precursor ideas to modern networking.</td></tr></tbody></table><h2 id="security" tabindex="-1"><a class="header-anchor" href="#security"><span>Security</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>2FA</td><td>Two-Factor Authentication â two independent proofs of identity.</td><td>Password + TOTP device.</td></tr><tr><td>ABAC</td><td>Attribute-Based Access Control â attribute-driven permissions.</td><td>Policies on user/resource attributes.</td></tr><tr><td>ACL</td><td>Access Control List â list of permissions attached to an object specifying which principals are allowed which operations.</td><td>Filesystem/network ACLs granting read/write/execute or allow/deny rules.</td></tr><tr><td>AES</td><td>Advanced Encryption Standard â widely used symmetric block cipher (Rijndael) with 128âbit blocks and 128/192/256âbit keys.</td><td>AESâGCM for TLS and atârest encryption.</td></tr><tr><td>BYOD</td><td>Bring Your Own Device â policy allowing use of personal devices for work, requiring security controls and management.</td><td>Enforce MDM, device compliance, and conditional access for email/apps.</td></tr><tr><td>BYOK</td><td>
1Bring Your Own Key â customer-managed encryption keys used with a cloud providerâs services instead of providerâmanaged keys.</td><td>Store CMKs in KMS/HSM; configure services to use them; rotate regularly.</td></tr><tr><td>CA</td><td>Certificate Authority â issues digital certificates (X.509).</td><td>Let's Encrypt TLS certs.</td></tr><tr><td>CFI</td><td>Control-Flow Integrity â restricts indirect branches/returns to valid targets to thwart codeâreuse attacks (ROP/JOP).</td><td>LLVM/Clang CFI, Intel CET/IBT, ARM Pointer Authentication (PAC) harden control flow.</td></tr><tr><td>CORS</td><td>Cross-Origin Resource Sharing â control cross-site requests.</td><td>Allow specific origins/headers.</td></tr><tr><td>CSP</td><td>Content Security Policy â control resource loading; mitigate XSS.</td><td><code>default-src 'self'</code>.</td></tr><tr><td>CSRF</td><td>Cross-Site Request Forgery â unintended actions by a victim.</td><td>CSRF tokens, same-site cookies.</td></tr><tr><td>CVE</td><td>Common Vulnerabilities and Exposures â public identifier for disclosed security issues.</td><td>CVE-2024-XXXXX referenced in advisories and patches.</td></tr><tr><td>DAST</td><td>Dynamic App Security Testing â test running apps.</td><td>Zap/Burp scans.</td></tr><tr><td>DDoS</td><td>Distributed Denial of Service â many-source DoS.</td><td>Botnet floods traffic.</td></tr><tr><td>DKIM</td><td>DomainKeys Identified Mail â cryptographic email authentication using domain-signed headers.</td><td>Receivers verify DKIM-Signature with the sender's DNS key.</td></tr><tr><td>DMARC</td><td>Domain-based Message Authentication, Reporting, and Conformance â email authentication policy leveraging SPF and DKIM with alignment and reporting.</td><td>Publish <code>v=DMARC1; p=quarantine; rua=mailto:[email protected]</code>.</td></tr><tr><td>DoS</td><td>Denial of Service â make a service unavailable.</td><td>Single-source flood.</td></tr><tr><td>DRM</td><td>Digital Rights Management â technologies to control access, copying, and usage of digital content via encryption and licensing.</td><td>Browser EME with Widevine/PlayReady; app checks license server before playback.</td></tr><tr><td>GPG</td><td>GNU Privacy Guard â OpenPGP implementation.</td><td><code>gpg --sign --encrypt file</code>.</td></tr><tr><td>HMAC</td><td>Hash-based Message Authentication Code â keyed hash for message integrity and authenticity.</td><td>HMACâSHA256 for API request signing; JWT HS256.</td></tr><tr><td>HSM</td><td>Hardware Security Module â tamperâresistant hardware appliance or cloud service for secure key generation, storage, and cryptographic operations with strong access controls and auditing.</td><td>Use an HSM/KMS to generate and store TLS/CA private keys; perform signing inside the module.</td></tr><tr><td>HSTS</td><td>HTTP Strict Transport Security â force HTTPS for a period.</td><td><code>Strict-Transport-Security</code> header.</td></tr><tr><td>IAM</td><td>Identity and Access Management â users/roles/permissions.</td><td>Cloud IAM policies.</td></tr><tr><td>IDS</td><td>Intrusion Detection System â monitors networks/hosts for malicious activity or policy violations, generating alerts for investigation.</td><td>Network IDS like Zeek/Snort; host IDS like OSSEC/Wazuh; alert to SIEM.</td></tr><tr><td>IPS</td><td>Intrusion Prevention System â inline security control that inspects traffic/events and can automatically block or remediate detected threats.</td><td>IPS mode in nextâgen firewalls; Snort/Suricata inline dropping malicious packets.</td></tr><tr><td>JWT</td><td>
1JSON Web Token â compact auth/claims token.</td><td><code>Authorization: Bearer <jwt></code>.</td></tr><tr><td>MAC</td><td>Message Authentication Code â short, fixed-length tag produced from a message and secret key that enables verification of message integrity and authenticity.</td><td>Compute an AES-CMAC or HMAC-SHA256 over API payloads; receivers recompute the MAC to detect tampering.</td></tr><tr><td>MDM</td><td>Mobile Device Management â administer and secure mobile/end-user devices via policies, enrollment, and remote actions.</td><td>Enforce passcodes, disk encryption, app whitelists; remote wipe on loss.</td></tr><tr><td>MFA</td><td>Multi-Factor Authentication â 2+ factors.</td><td>Password + hardware key.</td></tr><tr><td>MITM</td><td>Man-In-The-Middle â intercept/alter comms.</td><td>Rogue Wi-Fi AP sniffing.</td></tr><tr><td>mTLS</td><td>Mutual TLS â both client and server present certificates.</td><td>Service-to-service auth in meshes.</td></tr><tr><td>NX</td><td>No-eXecute bit â CPU feature that marks memory pages as non-executable to prevent code execution from data segments like the stack and heap.</td><td>OS sets the NX bit on the stack to mitigate buffer overflows; also known as DEP/XD/W^X.</td></tr><tr><td>OAuth</td><td>Delegated authorization protocol.</td><td>Access token for API calls.</td></tr><tr><td>OIDC</td><td>OpenID Connect â identity layer over OAuth 2.0.</td><td>ID token for login.</td></tr><tr><td>OTP</td><td>One-Time Password â shortâlived code used for authentication; delivered or generated per login.</td><td>Appâgenerated TOTP/HOTP codes; avoid SMS OTP when possible.</td></tr><tr><td>PGP</td><td>Pretty Good Privacy â encryption/signing format.</td><td>Email encryption/signing.</td></tr><tr><td>PKCS</td><td>Public-Key Cryptography Standards â RSA-led standards defining formats and algorithms used in public-key crypto.</td><td>PKCS #1 (RSA), #7/CMS (cryptographic messages), #8 (private keys), #12 (PFX/P12), #5 (PBES), #10 (CSR).</td></tr><tr><td>PKI</td><td>Public Key Infrastructure â system of CAs, certs, keys, and policies.</td><td>Issue and validate X.509 certs.</td></tr><tr><td>PoLP</td><td>Principle of Least Privilege â grant only the minimum permissions necessary for a user or system to perform its function.</td><td>IAM roles with narrowly scoped permissions; run services as non-root users.</td></tr><tr><td>RBAC</td><td>Role-Based Access Control â role-granted permissions.</td><td>Admin/Editor/Viewer roles.</td></tr><tr><td>RCE</td><td>Remote Code Execution â run arbitrary code remotely.</td><td>Deserialization exploit.</td></tr><tr><td>ROP</td><td>Return-Oriented Programming â code reuse attack that chains existing instruction sequences ("gadgets") ending in <code>ret</code> to execute arbitrary code, bypassing DEP/NX.</td><td>Chain ROP gadgets from loaded libraries to call <code>mprotect</code> and make the stack executable.</td></tr><tr><td>RSA</td><td>RivestâShamirâAdleman â widely used publicâkey cryptosystem for encryption and signatures.</td><td>2048âbit RSA keys; RSAâPKCS#1 signatures; TLS certs.</td></tr><tr><td>SAM</td><td>Security Accounts Manager â the database in Windows that stores user passwords (as hashes) and security principals.</td><td>The SAM file (<code>%SystemRoot%/system32/config/SAM</code>); <code>lsass.exe</code> protects it.</td></tr><tr><td>SAST</td><td>Static App Security Testing â analyze code/binaries.</td><td>SAST pipeline checks.</td></tr><tr><td>SBOM</td><td>Software Bill of Materials â inventory of components, dependencies, and versions in software artifacts for transparency and vulnerability management.</td><td>Generate CycloneDX/SPDX SBOMs in CI; scan against CVEs.</td></tr><tr><td>SFI</td><td>Software Fault Isolation â security technique that sandboxes untrusted code by rewriting its machine code to prevent it from accessing memory or calling functions outside its designated region.</td><td>Google Native Client (NaCl) uses SFI to safely run native code in the browser.</td></tr><tr><td>SHA</td><td>Secure Hash Algorithm â family of cryptographic hash functions (SHAâ2/256/512; SHAâ3/Keccak).</td><td>TLS cert signatures, file integrity checks; Git moving from SHAâ1 to SHAâ256.</td></tr><tr><td>SPF</td><td>Sender Policy Framework â DNS-based mechanism to authorize mail servers for a domain.</td><td><code>v=spf1 ip4:203.0.113.0/24 -all</code> record.</td></tr><tr><td>SQLi</td><td>SQL Injection â inject SQL via input.</td><td>Parameterized queries prevent it.</td></tr><tr><td>SSH</td><td>Secure Shell â encrypted remote login/exec.</td><td><code>ssh user@host</code>.</td></tr><tr><td>SSO</td><td>Single Sign-On â authenticate once, access many apps.</td><td>SAML/OIDC-based SSO.</td></tr><tr><td>SSRF</td><td>Server-Side Request Forgery â trick server to make requests.</td><td>Block metadata endpoints.</td></tr><tr><td>TLS</td><td>Transport Layer Security â secure comms.</td><td>HTTPS uses TLS.</td></tr><tr><td>TOTP</td><td>Time-Based One-Time Password â time-synced one-time codes.</td><td>Authenticator app 6-digit codes.</td></tr><tr><td>XSRF</td><td>Alternate name for CSRF in some frameworks.</td><td>Angular XSRF-TOKEN cookie/header.</td></tr><tr><td>XSS</td><td>Cross-Site Scripting â script injection into pages.</td><td>Output encoding, CSP.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>MD5</td><td>Message Digest Algorithm 5 â legacy 128-bit cryptographic hash function; cryptographically broken (collisions) and unsuitable for security, but still used for checksums.</td><td><code>md5sum file.iso</code> to verify integrity; avoid for passwords/signatures.</td></tr><tr><td>NTLM</td><td>NT LAN Manager â a legacy Microsoft authentication protocol suite, superseded by Kerberos.</td><td>Windows workgroup authentication; fallback when Kerberos is unavailable.</td></tr><tr><td>RACF</td><td>Resource Access Control Facility â the primary security system on IBM mainframes (z/OS), controlling access to datasets, applications, and system resources.</td><td>Define user profiles and grant dataset access with RACF commands.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>SSL</td><td>Secure Sockets Layer â legacy to TLS.</td><td>Deprecated; use TLS.</td></tr></tbody></table><h2 id="privacy" tabindex="-1"><a class="header-anchor" href="#privacy"><span>Privacy</span></a></h2><table><thead><tr><th>
1Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>CCPA</td><td>California Consumer Privacy Act â US privacy law granting rights to access, delete, and opt out of sale of personal data.</td><td>Add Do Not Sell link; handle access/deletion requests.</td></tr><tr><td>CPRA</td><td>California Privacy Rights Act â amends/expands CCPA with new rights (correction), sensitive data category, and the CPPA regulator.</td><td>Honor opt-out for sharing; handle sensitive PI with limits.</td></tr><tr><td>DSAR</td><td>Data Subject Access Request â request by an individual to access, correct, delete, or obtain a copy of their personal data.</td><td>Process access/erasure/portability requests within statutory timelines.</td></tr><tr><td>GDPR</td><td>General Data Protection Regulation â EU law governing personal data protection, rights, and obligations.</td><td>Lawful basis, DPO, DPIA; data subject rights (access/erasure/portability).</td></tr><tr><td>HIPAA</td><td>Health Insurance Portability and Accountability Act â US law setting privacy/security standards for protected health information (PHI).</td><td>Covered entities sign BAAs; apply the HIPAA Privacy/Security Rules.</td></tr><tr><td>PII</td><td>Personally Identifiable Information â data that can identify an individual; subject to privacy laws and safeguards.</td><td>Names, emails, SSNs; apply minimization, masking, and access controls.</td></tr></tbody></table>
1<h2 id="infrastructure" tabindex="-1"><a class="header-anchor" href="#infrastructure"><span>Infrastructure</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AD</td><td>Active Directory â Microsoft identity directory service.</td><td>Centralized auth/authorization.</td></tr><tr><td>CDN</td><td>Content Delivery Network â globally distributed cache.</td><td>Faster static asset delivery.</td></tr><tr><td>DNS</td><td>Domain Name System â resolve names to IPs.</td><td><code>A</code>, <code>AAAA</code>, <code>CNAME</code> records.</td></tr><tr><td>DNSSEC</td><td>Domain Name System Security Extensions â adds origin authentication and data integrity to DNS using digital signatures (RRSIG) validated via a chain of trust from signed zones and DS records.</td><td>Sign zones with ZSK/KSK; validators check RRSIGs and DS chain from the root; prevents cache poisoning/spoofing.</td></tr><tr><td>FaaS</td><td>Function as a Service â serverless functions.</td><td>AWS Lambda handlers.</td></tr><tr><td>FQDN</td><td>Fully Qualified Domain Name â complete, absolute domain name that specifies all labels up to the root.</td><td><code>host1.db.eu-west.example.com.</code> (trailing dot optional in practice).</td></tr><tr><td>HPC</td><td>High-Performance Computing â parallel, large-scale compute using clusters/supercomputers for scientific/engineering workloads.</td><td>Run MPI/Slurm jobs on a GPU/CPU cluster with InfiniBand.</td></tr><tr><td>IaaS</td><td>Infrastructure as a Service â virtual compute/storage/network.</td><td>EC2/Compute Engine.</td></tr><tr><td>IaC</td><td>Infrastructure as Code â manage infrastructure with code and VCS.</td><td>Use Terraform to provision cloud resources via PRs.</td></tr><tr><td>IoT</td><td>Internet of Things â networked embedded devices and sensors that collect data and interact with the physical world.</td><td>MQTT devices sending telemetry to an IoT hub.</td></tr><tr><td>K8S</td><td>Kubernetes â container orchestration.</td><td><code>kubectl get pods</code>.</td></tr><tr><td>KMS</td><td>Key Management Service â managed key storage and cryptographic operations.</td><td>AWS KMS for envelope encryption and key rotation.</td></tr><tr><td>KVM</td><td>Kernel-based Virtual Machine â Linux kernel virtualization enabling VMs with hardware acceleration via KVM modules.</td><td>Run QEMU with KVM for near-native performance; manage with libvirt/virt-manager.</td></tr><tr><td>LB</td><td>Load Balancer â distributes traffic across multiple backends for scalability and resilience.</td><td>AWS ALB/NLB, HAProxy/Nginx with health checks and stickiness.</td></tr><tr><td>LXC</td><td>Linux Containers â OS-level virtualization using cgroups/namespaces to isolate processes.</td><td>Run lightweight containers without a separate kernel per instance.</td></tr><tr><td>MPI</td><td>Message Passing Interface â standardized API for distributed-memory parallel programming using processes that communicate via messages.</td><td>Launch ranks with <code>mpirun</code> (OpenMPI/MPICH); use collectives like <code>MPI_Bcast</code>/<code>MPI_Reduce</code>.</td></tr><tr><td>NAS</td><td>Network-Attached Storage â dedicated file storage accessible over a network.</td><td>Home/SMB NAS appliances exposing NFS/SMB shares.</td></tr><tr><td>OCI</td><td>Open Container Initiative â specs for container images and runtimes.</td><td>OCI Image format and OCI Runtime (runc).</td></tr><tr><td>PaaS</td><td>Platform as a Service â deploy apps without infra mgmt.</td><td>Heroku, App Engine.</td></tr><tr><td>QEMU</td><td>Quick EMUlator â open-source machine emulator and virtualizer supporting full-system emulation and hardware-accelerated virtualization across many architectures.</td><td>Boot ARM or RISC-V guests with <code>qemu-system-*</code>; pair with KVM for x86 virtualization on Linux hosts.</td></tr><tr><td>SaaS</td><td>Software as a Service â subscription-based software.</td><td>Hosted CRM/Email.</td></tr><tr><td>SAN</td><td>Storage Area Network â high-speed network providing block-level storage access to servers.</td><td>Fibre Channel/iSCSI SAN for shared volumes.</td></tr><tr><td>SIMH</td><td>Simulator for Historical Computers â open-source emulator suite for classic minicomputers/mainframes (PDP-11, VAX, IBM 1401, etc.), preserving vintage software environments.</td><td>Boot a PDP-11 running RT-11/RSX or a VAX/VMS system image for retrocomputing and software archaeology.</td></tr><tr><td>TCG</td><td>Tiny Code Generator â QEMU's dynamic binary translation engine that recompiles guest CPU instructions into host machine code at runtime when hardware acceleration isn't available.</td><td>Run QEMU in pure emulation mode; TCG translates ARM guest opcodes to x86 host instructions on the fly.</td></tr><tr><td>UPS</td><td>Uninterruptible Power Supply â device providing battery-backed power to keep equipment running through short outages and allow graceful shutdown.<
1/td><td>Rack UPS for servers/network gear; runtime and VA/W ratings.</td></tr><tr><td>VM</td><td>Virtual Machine â emulated hardware environment to run OS instances.</td><td>KVM/Hyper-V VMs for isolation.</td></tr><tr><td>VPC</td><td>Virtual Private Cloud â isolated virtual network.</td><td>Subnets, route tables, SGs.</td></tr><tr><td>VPN</td><td>Virtual Private Network â secure tunnel.</td><td>Site-to-site/client VPN.</td></tr></tbody></table><h2 id="hardware-architecture" tabindex="-1"><a class="header-anchor" href="#hardware-architecture"><span>Hardware (Architecture)</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AMD64</td><td>64-bit x86 architecture introduced by AMD (aka x86-64, adopted by Intel as Intel 64) extending IA-32 with 64-bit registers, more general-purpose registers, and long mode.</td><td>Build for <code>x86_64</code>/<code>amd64</code>; Linux System V AMD64 ABI; Windows x64 with WOW64 for 32-bit apps.</td></tr><tr><td>ARM</td><td>Advanced RISC Machines â 32-bit RISC architecture (AArch32) originating from Acorn, spanning ARMv1-v7 cores widely used in mobile, embedded, and microcontroller systems.</td><td>Cross-compile for <code>armv7</code>/<code>armhf</code>; run 32-bit ARM Linux on Raspberry Pi models or Cortex-M firmware.</td></tr><tr><td>ARM64</td><td>64-bit ARM architecture (aka AArch64, ARMv8-A and later) with a new instruction set and execution state distinct from 32-bit ARM (AArch32).</td><td>Build for <code>arm64</code>/<code>aarch64</code>; Apple Silicon Macs, AWS Graviton/Neoverse servers, Android flagship SoCs.</td></tr><tr><td>ASIC</td><td>Application-Specific Integrated Circuit â a chip customized for a particular use, rather than for general-purpose use like a CPU.</td><td>Bitcoin mining ASICs; Google TPU for machine learning.</td></tr><tr><td>CHERI</td><td>Capability Hardware Enhanced RISC Instructions â architectural extensions that add tagged, unforgeable capabilities to enforce fineâgrained memory safety and compartmentalization.</td><td>CHERIâRISCâV/MIPS; pointers carry bounds/permissions; safer C/C++ and sandboxing.</td></tr><tr><td>CISC</td><td>
1Complex Instruction Set Computer â CPU design approach featuring larger, more complex, and variableâlength instructions, often implemented with microcode.</td><td>x86/x86â64 architectures; <code>REP MOVS</code>, string ops, rich addressing modes.</td></tr><tr><td>CUDA</td><td>Compute Unified Device Architecture â NVIDIA's parallel computing platform and programming model for GPUs.</td><td>Launch kernels in CUDA C++; PyTorch/TensorFlow GPU ops.</td></tr><tr><td>EM64T</td><td>Extended Memory 64 Technology â Intelâs original branding for its AMD64âcompatible 64âbit x86 implementation, now marketed as Intel 64.</td><td>Intel Core/Xeon CPUs report Intel 64; target <code>x86_64</code> in toolchains.</td></tr><tr><td>IA-32</td><td>32âbit Intel architecture â the classic 32âbit x86 ISA (i386 and successors) with protected mode, paging, and SSE-era extensions; predecessor to x86â64.</td><td>Build for <code>x86</code>/<code>i386</code>/<code>i686</code>; 32âbit OSes/apps, WOW64 on Windows x64, multilib on Linux.</td></tr><tr><td>ISA</td><td>Instruction Set Architecture â contract describing a CPUâs instructions, registers, memory model, and privilege levels; distinct from microarchitecture.</td><td>x86â64, ARMv8âA; RISCâV RV64GC with optional extensions.</td></tr><tr><td>MIPS</td><td>Microprocessor without Interlocked Pipeline Stages â classic RISC architecture used in embedded systems, networking gear, and historically in workstations/servers.</td><td>MIPS32/MIPS64 in routers and embedded devices; historical SGI workstations/IRIX.</td></tr><tr><td>NUMA</td><td>Non-Uniform Memory Access â architecture where memory access latency and bandwidth vary depending on whether memory is local to a CPU socket/node or remote.</td><td>Pin threads and allocate memory per NUMA node (e.g., <code>numactl</code>) to reduce cross-socket traffic.</td></tr><tr><td>PA-RISC</td><td>Precision Architecture RISC â HewlettâPackardâs RISC architecture used in HP 9000 servers/workstations, largely superseded by Itanium and then x86â64.</td><td>HPâUX on PAâRISC systems (e.g., PAâ8700/8900); historical HP 9000 platforms.</td></tr><tr><td>POWER</td><td>IBM Performance Optimization With Enhanced RISC â IBMâs RISC architecture family used in servers/workstations (POWER4+), distinct but related to the PowerPC lineage.</td><td>IBM Power Systems running AIX/IBM i/Linux; POWER9/POWER10 CPUs.</td></tr><tr><td>PPC</td><td>PowerPC â RISC CPU architecture developed by the AIM alliance (AppleâIBMâMotorola), used in desktops historically and widely in embedded/console systems.</td><td>PowerPC 32/64âbit (POWER/PowerPC); GameCube/Wii/PS3; embedded/controllers.</td></tr><tr><td>RISC</td><td>Reduced Instruction Set Computer â CPU design philosophy emphasizing a small, simple instruction set and efficient pipelines.</td><td>ARM and RISC-V architectures.</td></tr><tr><td>RISC-V</td><td>Open standard RISC instruction set architecture with modular extensions (e.g., I/M/A/F/D/V) and 32/64/128âbit variants (RV32/64/128); free to implement without licensing.</td><td>Microcontrollers to servers; Linux on RV64GC; chips from SiFive, Andes; SBCs and accelerators.</td></tr><tr><td>SMP</td><td>Symmetric Multiprocessing â architecture where multiple identical CPUs/cores share the same memory and OS, enabling parallel execution of threads/processes.</td><td>Multi-core x86/ARM systems; OS scheduler runs threads across cores with shared memory.</td></tr><tr><td>SPARC</td><td>Scalable Processor ARChitecture â RISC CPU architecture originally developed by Sun Microsystems, widely used in servers/workstations and embedded systems.</td><td>SPARC V8/V9 (32/64âbit); UltraSPARC/Oracle SPARC running Solaris/illumos.</td></tr><tr><td>X86-64</td><td>Generic name for the 64âbit x86 ISA (defined by AMD as AMD64 and implemented by Intel as Intel 64/EM64T); adds 64âbit mode and more registers over IAâ32.</td><td>Build for <code>x86_64</code>; 64âbit OSes and apps on AMD/Intel processors.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>AT</td><td>Advanced Technology â the IBM PC/AT was the successor to the XT, introducing the 16-bit ISA bus, the 286 processor, and the AT keyboard connector.</td><td>The AT form factor and motherboard design influenced PCs for years.</td></tr><tr><td>CD-i</td><td>Compact Disc Interactive â a multimedia CD player and platform developed by Philips and Sony.</td><td>Known for its games and educational titles in the early 1990s.</td></tr><tr><td>IA-64</td><td>Intel Itanium architecture â 64âbit EPIC (Explicitly Parallel Instruction Computing) ISA developed by Intel/HP; distinct from x86/x86â64 and now discontinued.</td><td>Itanium servers/workstations running HPâUX, OpenVMS, and legacy Windows Server for Itaniumâbased systems.</td></tr><tr><td>MSX</td><td>Machines with Software eXchangeability â a standardized home computer architecture from the 1980s.</td><td>Popular in Japan and Europe; Konami games on MSX.</td></tr><tr><td>PDP</td><td>Programmed Data Processor â DEC minicomputer line before VAX.</td><td>PDPâ8, PDPâ11 systems.</td></tr><tr><td>VAX</td><td>Virtual Address eXtension â DEC 32âbit minicomputer architecture.</td><td>VAX/VMS systems in universities and industry.</td></tr><tr><td>XT</td><td>Extended Technology â the IBM PC XT was an early version of the PC that included a hard drive.</td><td>The 8-bit bus architecture of the PC/XT.</td></tr></tbody></table><h2 id="hardware-cpu-general" tabindex="-1"><a class="header-anchor" href="#hardware-cpu-general"><span>Hardware (CPU / General)</span></a></h2><table><thead><tr><th>
1Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>ALU</td><td>Arithmetic Logic Unit â digital circuit in the CPU that performs integer arithmetic and bitwise operations.</td><td>Add, subtract, AND/OR/XOR, shifts/rotates executed by the ALU pipelines.</td></tr><tr><td>AP</td><td>Application Processor â any nonâbootstrap CPU core in an SMP system that is brought online by the BSP to run the OS scheduler and workloads.</td><td>OS sends INIT/SIPI to start APs after BSP init; threads scheduled across APs.</td></tr><tr><td>BSP</td><td>Bootstrap Processor â on multi-processor systems (e.g., x86 SMP), the primary CPU core that starts executing firmware/boot code and brings up the OS, which then initializes the remaining cores as Application Processors (APs).</td><td>Firmware runs on the BSP first; OS sends INIT/SIPI to start APs.</td></tr><tr><td>CPU</td><td>Central Processing Unit â main processor that executes instructions.</td><td>x86-64 CPUs with multiple cores/threads and SIMD.</td></tr><tr><td>FPU</td><td>Floating Point Unit â hardware for floating-point arithmetic.</td><td>IEEE 754 operations, SIMD extensions.</td></tr><tr><td>L1/L2/L3</td><td>Level 1/2/3 Cache â hierarchical caches in a CPU that store frequently accessed data to reduce latency to main memory.</td><td>L1 is fastest/smallest (per-core I/D); L2 is larger (per-core); L3 is largest (shared).</td></tr><tr><td>MMU</td><td>Memory Management Unit â hardware for virtual memory and address translation.</td><td>x86-64 paging with TLBs.</td></tr><tr><td>NMI</td><td>Non-Maskable Interrupt â high-priority hardware interrupt that cannot be disabled by normal interrupt masking, used for critical fault or watchdog conditions.</td><td>Watchdog parity/ECC errors trigger NMI; OS NMI handler logs/diagnoses hangs.</td></tr><tr><td>SIMD</td><td>Single Instruction, Multiple Data â vector parallelism executing the same instruction across multiple data lanes.</td><td>SSE/AVX on x86, NEON on ARM.</td></tr><tr><td>TLB</td><td>Translation Lookaside Buffer â small cache of virtualâphysical address translations used by the MMU.</td><td>TLB hits speed up paging; TLB flush on context switch.</td></tr></tbody></table><h2 id="hardware-cpu-arm" tabindex="-1"><a class="header-anchor" href="#hardware-cpu-arm"><span>Hardware (CPU / ARM)</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>EL0/1/2/3</td><td>Exception Levels â ARMv8 privilege levels: EL0 (unprivileged), EL1 (OS kernel), EL2 (hypervisor), EL3 (secure monitor).</td><td>User apps run at EL0; the kernel at EL1; KVM at EL2.</td></tr><tr><td>GIC</td><td>Generic Interrupt Controller â standard ARM architecture for managing interrupts, routing them from peripherals to CPU cores.</td><td>GICv2/v3/v4; the ARM equivalent of x86's APIC.</td></tr><tr><td>NEON</td><td>ARM's advanced SIMD (Single Instruction, Multiple Data) architecture extension for accelerating multimedia and signal processing.</td><td>NEON intrinsics for video encoding; equivalent to x86 SSE/AVX.</td></tr><tr><td>SVE</td><td>Scalable Vector Extension â next-generation SIMD instruction set for ARM AArch64, designed for HPC with vector-length agnostic programming.</td><td>High-performance computing workloads on ARM servers.</td></tr></tbody></table><h2 id="hardware-cpu-x86" tabindex="-1"><a class="header-anchor" href="#hardware-cpu-x86"><span>Hardware (CPU / x86)</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AMX</td><td>Advanced Matrix Extensions â x86 instruction set extensions providing tiled matrix operations accelerated in hardware.</td><td>Intel AMX for deepâlearning inference/training (tile registers, TMUL).</td></tr><tr><td>APIC</td><td>Advanced Programmable Interrupt Controller â modern local/IO APICs providing scalable interrupt delivery in SMP systems.</td><td>LAPIC per core and IOAPIC for external IRQs on x86.</td></tr><tr><td>AVX</td><td>Advanced Vector Extensions â x86 SIMD instruction set extensions for wide vector operations (256/512-bit in AVX/AVX-512).</td><td>AVX2 for integer ops; AVX-512 for HPC workloads.</td></tr><tr><td>SSE</td><td>Streaming SIMD Extensions â x86 SIMD instruction set extensions for parallel vector operations.</td><td>SSE2/SSE4 intrinsics; compiler autovectorization for math/graphics.</td></tr><tr><td>VMX</td><td>Virtual Machine Extensions â Intel x86 virtualization extensions (VTâx) that add CPU modes/instructions (VMX root/nonâroot, VMXON/VMXOFF, VMLAUNCH/VMRESUME) and a VMCS for hardwareâassisted virtualization.</td><td>Enable VTâx in firmware; KVM/HyperâV/VMware use VMX to run guests with hardware assist.</td></tr><tr><td>xAPIC</td><td>Extended APIC â the default operational mode for the modern x86 APIC, using MMIO for register access.</td><td>The OS maps the LAPIC's MMIO region to send IPIs and manage local interrupts.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>MMX</td><td>MultiMedia eXtensions â early x86 SIMD instruction set for integer vector operations.</td><td>Legacy MMX ops predating SSE on Pentium-era CPUs.</td></tr></tbody></table><h2 id="hardware-memory" tabindex="-1"><a class="header-anchor" href="#hardware-memory"><span>Hardware (Memory)</span></a></h2><table><thead><tr><th>
1Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>DDR</td><td>Double Data Rate â class of synchronous DRAM that transfers data on both clock edges for higher bandwidth.</td><td>DDR4/DDR5 SDRAM in modern systems.</td></tr><tr><td>DIMM</td><td>Dual Inline Memory Module â standardized memory module form factor for SDRAM.</td><td>288âpin DDR4/DDR5 DIMMs.</td></tr><tr><td>DRAM</td><td>Dynamic Random Access Memory â volatile memory storing bits in capacitors that require periodic refresh.</td><td>Main system memory (SDRAM/DDR).</td></tr><tr><td>ECC</td><td>Error-Correcting Code memory â memory modules/chipsets that detect and correct singleâbit errors (and detect some multiâbit errors) to improve reliability.</td><td>ECC UDIMMs/RDIMMs in servers/workstations; machine check logs corrected errors.</td></tr><tr><td>EEPROM</td><td>Electrically Erasable Programmable Read-Only Memory â non-volatile memory that can be electrically erased and reprogrammed at the byte/page level; used for small configuration storage and microcontroller data.</td><td>I²C/SPI EEPROMs (24xx/25xx series); MCU calibration data; distinct from flash (block erase).</td></tr><tr><td>GDDR</td><td>Graphics Double Data Rate â highâbandwidth memory variants optimized for GPUs and graphics workloads.</td><td>GDDR6/GDDR6X on modern GPUs; wide buses and high data rates.</td></tr><tr><td>HBM</td><td>High Bandwidth Memory â stacked memory connected via wide interfaces onâpackage for very high bandwidth and energy efficiency.</td><td>HBM2/HBM3 on AI/ML accelerators and highâend GPUs.</td></tr><tr><td>LPDDR</td><td>Low-Power DDR â mobile/embedded DRAM optimized for low power with deep power states and wide IO at low voltage.</td><td>LPDDR4/4X/5/5X in smartphones, tablets, ultrabooks, and SoCs.</td></tr><tr><td>NVRAM</td><td>Non-Volatile RAM â memory that retains data without power; implemented via flash, EEPROM, or batteryâbacked SRAM; often stores firmware variables/settings.</td><td>UEFI variables in NVRAM; macOS NVRAM for boot args and device settings.</td></tr><tr><td>RAM</td><td>Random Access Memory â volatile memory used for working data and code.</td><td>DDR4/DDR5 DIMMs.</td></tr><tr><td>ROM</td><td>Read-Only Memory â non-volatile memory storing firmware or static data.</td><td>Boot ROM, option ROMs.</td></tr><tr><td>SDRAM</td><td>Synchronous Dynamic Random Access Memory â DRAM synchronized with the system clock, enabling pipelined access and higher throughput versus asynchronous DRAM.</td><td>PC100/PC133 SDRAM; basis for modern DDR (DDR/DDR2/3/4/5).</td></tr><tr><td>SO-DIMM</td><td>Small Outline Dual Inline Memory Module â compact memory module form factor used in laptops and small form-factor systems; electrically similar to DIMMs but physically smaller and not interchangeable.</td><td>DDR4/DDR5 SOâDIMMs in laptops/NUCs; shorter modules with different keying.</td></tr><tr><td>SRAM</td><td>Static Random Access Memory â volatile memory using flip-flops; fast and does not need refresh.</td><td>CPU caches (L1/L2/L3) implemented with SRAM.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>EDO</td><td>Extended Data Out DRAM â improved asynchronous DRAM that allows the data output to remain valid longer, enabling slightly higher performance than FPM before SDRAM became mainstream.</td><td>Midâ1990s 486/Pentium systems with EDO SIMMs; replaced by SDRAM.</td></tr><tr><td>EPROM</td><td>Erasable Programmable Read-Only Memory â UV-erasable ROM chips with a quartz window; erased under UV light and reprogrammed with a programmer.</td><td>27xx-series EPROMs in retro computers/arcade boards; UV eraser tools.</td></tr><tr><td>FPM</td><td>Fast Page Mode DRAM â asynchronous DRAM access mode that speeds up accesses within the same row/page compared to plain DRAM; predecessor to EDO and SDRAM.</td><td>Early 1990s SIMM modules using FPM; superseded by EDO/SDRAM.</td></tr><tr><td>PROM</td><td>Programmable Read-Only Memory â one-time programmable ROM that can be programmed once after manufacturing and cannot be erased.</td><td>82S/27S series PROMs used for microcode/firmware; fuse/antifuse technologies.</td></tr><tr><td>RDRAM</td><td>Rambus DRAM â highâbandwidth DRAM technology from Rambus used with RIMM modules and a packetized, narrow bus; briefly mainstream on Pentium 4 before being displaced by DDR SDRAM.</td><td>RIMM modules in Intel i850/i850E chipsets; now obsolete in favor of DDR/DDR2+.</td></tr><tr><td>RIMM</td><td>Rambus Inline Memory Module â module form factor for RDRAM with continuity requirements (CRIMMs in empty slots) and heat spreaders; used briefly in earlyâ2000s PCs/servers.</td><td>Populate paired RIMMs on i850 boards; install CRIMMs in unused slots; now obsolete.</td></tr><tr><td>SIMM</td><td>Single Inline Memory Module â older memory module form factor with a single set of contacts; used with FPM/EDO/early SDRAM.</td><td>30âpin/72âpin SIMMs on 386/486/Pentium-era systems.</td></tr></tbody></table><h2 id="hardware-buses-interfaces" tabindex="-1"><a class="header-anchor" href="#hardware-buses-interfaces"><span>Hardware (Buses & Interfaces)</span></a></h2><table><thead><tr><th>
1Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AHB</td><td>Advanced High-performance Bus â an AMBA bus protocol for connecting lower-performance peripherals.</td><td>Part of the on-chip bus fabric in an ARM SoC.</td></tr><tr><td>AMBA</td><td>Advanced Microcontroller Bus Architecture â a family of on-chip interconnect specifications for connecting functional blocks in an SoC.</td><td>AMBA protocols include AXI, AHB, and APB.</td></tr><tr><td>APB</td><td>Advanced Peripheral Bus â a low-bandwidth AMBA bus protocol for simple peripherals.</td><td>Connecting UARTs, GPIO, and timers in an SoC.</td></tr><tr><td>AXI</td><td>Advanced eXtensible Interface â a high-performance AMBA bus protocol for demanding components like CPUs, GPUs, and memory controllers.</td><td>The main high-speed bus in a modern ARM SoC.</td></tr><tr><td>CCIX</td><td>Cache Coherent Interconnect for Accelerators â an industry standard for coherent interconnects between processors and accelerators.</td><td>Connecting FPGAs or GPUs to an ARM server CPU.</td></tr><tr><td>CMN</td><td>Coherent Mesh Network â ARM's high-performance mesh interconnect for connecting components within an SoC and between multiple SoCs.</td><td>The socket-to-socket interconnect in multi-socket ARM servers.</td></tr><tr><td>DMI</td><td>Direct Media Interface â Intel's proprietary link between a CPU and the Platform Controller Hub (PCH).</td><td>DMI 3.0/4.0 providing bandwidth for peripherals connected to the PCH.</td></tr><tr><td>GPIO</td><td>General-Purpose Input/Output â configurable digital pins on microcontrollers/SoCs used for reading inputs and driving outputs; often support pullâups/downs and interrupts.</td><td>Toggle Raspberry Pi GPIO with <code>libgpiod</code>; configure pin mode and edge interrupts.</td></tr><tr><td>HBA</td><td>Host Bus Adapter â adapter that connects a host system to storage or network devices over a highâspeed bus/fabric (e.g., SAS, Fibre Channel).</td><td>FC/SAS HBAs in servers to attach SAN/storage arrays; visible via <code>lspci</code>.</td></tr><tr><td>HCI</td><td>Host Controller Interface â standardized command/event interface between a host stack and a hardware controller (notably in Bluetooth; also USB xHCI).</td><td>Capture Bluetooth HCI packets with <code>btmon</code>; interact via UART/USB HCI.</td></tr><tr><td>I2C</td><td>Inter-Integrated Circuit â a synchronous, multi-controller, multi-peripheral serial bus used for attaching low-speed peripherals to a motherboard or embedded system.</td><td>Connect sensors/EEPROMs to a microcontroller (SDA/SCL lines).</td></tr><tr><td>JTAG</td><td>Joint Test Action Group â industry standard for on-chip debugging, programming, and testing of integrated circuits.</td><td>Use a JTAG debugger to halt a CPU, inspect registers, and flash firmware.</td></tr><tr><td>MIDI</td><td>Musical Instrument Digital Interface â standard protocol/interface for transmitting musical performance data between instruments, controllers, and computers.</td><td>5âpin DIN or USBâMIDI; Note On/Off, Control Change; DAW controlling a synth.</td></tr><tr><td>PCI</td><td>Peripheral Component Interconnect â hardware bus standard for attaching peripherals.</td><td>PCI devices enumerated by bus/device/function.</td></tr><tr><td>PCIe</td><td>PCI Express â high-speed serial successor to PCI with lanes and links.</td><td>x16 GPU slot; NVMe drives over PCIe.</td></tr><tr><td>PS/2</td><td>Personal System/2 â legacy MiniâDIN interface for keyboards and mice on PCs.</td><td>PS/2 keyboard/mouse ports on motherboards/KVMs; supports NKRO without USB polling.</td></tr><tr><td>SPI</td><td>Serial Peripheral Interface â synchronous serial bus with master/slave (controller/peripheral) and separate data lines for full-duplex transfers.</td><td>Connect sensors/flash to microcontrollers (MOSI/MISO/SCLK/CS); higher speed than I²C.</td></tr><tr><td>UART</td><td>Universal Asynchronous Receiver-Transmitter â hardware for serial communication using asynchronous framing (start/stop bits) over TTL/RS-232 levels.</td><td>Debug console on microcontrollers; <code>/dev/ttyS*</code>/<code>/dev/ttyUSB*</code>; 115200 8N1.</td></tr><tr><td>UPI</td><td>Ultra Path Interconnect â Intel's current point-to-point processor interconnect for server CPUs, successor to QPI.</td><td>
1High-speed link between sockets on multi-processor Xeon systems.</td></tr><tr><td>USB</td><td>Universal Serial Bus â standard for cables and connectors between computers and peripherals.</td><td>USB 3.x devices; HID, storage, and serial classes.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>COM</td><td>Serial COM port â PC designation for RSâ232 serial interfaces (COM1/COM2/...), typically provided by 16550âclass UARTs on DBâ9 connectors.</td><td>Connect via nullâmodem/USBâserial; Windows <code>COM3:</code>; Linux <code>/dev/ttyS0</code> serial consoles.</td></tr><tr><td>LPC</td><td>Low Pin Count â a bus used on PC-compatible motherboards to connect low-bandwidth devices to the southbridge.</td><td>Connects the Super I/O chip, BIOS ROM, and TPM.</td></tr><tr><td>QPI</td><td>QuickPath Interconnect â Intel's point-to-point processor interconnect that replaced the FSB; superseded by UPI.</td><td>High-speed link between CPU and I/O hub on Nehalem/Sandy Bridge-E systems.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>BNC</td><td>Bayonet Neill-Concelman â coaxial RF connector with a quarter-turn bayonet lock, historically common for thin Ethernet, video, and instrumentation signals.</td><td>10BASE2 networks daisy-chained via BNC T-connectors with 50-ohm terminators; oscilloscopes and signal generators using BNC jacks.</td></tr><tr><td>EISA</td><td>Extended Industry Standard Architecture â 32-bit ISA-compatible bus developed by a consortium as an open alternative to MCA; supported bus mastering and IRQ sharing.</td><td>Server-class 486 systems with EISA expansion cards; later replaced by PCI.</td></tr><tr><td>FSB</td><td>Front-Side Bus â the main interface between the CPU and the northbridge in older PC architectures, superseded by on-chip memory controllers and point-to-point interconnects.</td><td>Pentium 4 on an 800MHz FSB; overclocking by raising the FSB speed.</td></tr><tr><td>ISA</td><td>Industry Standard Architecture â legacy 8/16âbit PC expansion bus.</td><td>Sound/IO cards on 286/386 era PCs.</td></tr><tr><td>LPT</td><td>Line Printer port â PC parallel printer interface (Centronics/IEEE 1284), addressed as LPT1/LPT2; largely obsolete.</td><td>Parallel printers and hardware dongles; DBâ25 connectors; IEEE 1284 SPP/EPP/ECP modes.</td></tr><tr><td>MCA</td><td>Micro Channel Architecture â IBM's proprietary 32âbit bus introduced with PS/2 systems as a successor to ISA; offered bus mastering and improved throughput but lacked industry adoption.</td><td>IBM PS/2 expansion cards;
1 supplanted by EISA/PCI.</td></tr><tr><td>PCMCIA</td><td>Personal Computer Memory Card International Association â the standard for laptop expansion cards (e.g., modems, network cards) before USB and ExpressCard.</td><td>Also known as PC Card; Type I/II/III cards.</td></tr><tr><td>Q-BUS</td><td>DEC Qâbus â asynchronous multiplexed address/data bus used in later PDPâ11 and early MicroVAX systems; lower-cost successor to Unibus with fewer signals.</td><td>Qâbus backplanes/peripherals in PDPâ11/23 and MicroVAX; legacy DEC minicomputers.</td></tr><tr><td>Unibus</td><td>DEC Unibus â early synchronous shared backplane bus interconnecting CPU, memory, and peripherals in PDPâ11 systems; predecessor to Qâbus.</td><td>PDPâ11 Unibus backplanes/peripherals; historical DEC minicomputers.</td></tr><tr><td>VLB</td><td>VESA Local Bus â highâspeed local bus before PCI.</td><td>486 motherboards with VLB video/IO cards.</td></tr><tr><td>VME</td><td>VMEbus (Versa Module Europa) â parallel backplane bus standard (IEEE 1014) widely used in embedded/industrial systems with Eurocard form factors (3U/6U) and modular CPU/I/O cards.</td><td>VME chassis in telecom, industrial control, and defense; CPU cards and I/O modules on a shared backplane.</td></tr></tbody></table><h2 id="hardware-storage" tabindex="-1"><a class="header-anchor" href="#hardware-storage"><span>Hardware (Storage)</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AHCI</td><td>Advanced Host Controller Interface â standard programming interface for SATA host controllers enabling features like NCQ, hot-plug, and native command queuing.</td><td>OS uses the AHCI driver; set SATA mode to AHCI in firmware for modern OS installs.</td></tr><tr><td>GPT</td><td>GUID Partition Table â modern disk partitioning scheme that supports large disks and many partitions, part of the UEFI standard.</td><td>Disks initialized with GPT instead of legacy MBR.</td></tr><tr><td>HDD</td><td>Hard Disk Drive â magnetic storage device with spinning platters and moving heads.</td><td>3.5"/2.5" SATA HDDs for bulk storage; higher latency than SSDs.</td></tr><tr><td>LBA</td><td>Logical Block Addressing â linear addressing scheme for block devices that replaces legacy CHS (Cylinder/Head/Sector) geometry.</td><td>512âbyte/4K sectors addressed by LBA; used by SATA/SCSI/NVMe.</td></tr><tr><td>LTO</td><td>Linear Tape-Open â open tape storage format for data backup/archive with generational roadmap (LTOâ1..LTOâ9), high capacity, and LTFS support.</td><td>LTOâ8/LTOâ9 tape drives/libraries in enterprise backups; use LTFS for fileâlike access.</td></tr><tr><td>LUN</td><td>Logical Unit Number â identifier addressing a logical unit (virtual disk) within a SCSI/iSCSI/Fibre Channel target, used for mapping storage to hosts.</td><td>Present LUNs from a SAN array to servers; host multipath to the same LUN.</td></tr><tr><td>NCQ</td><td>Native Command Queuing â SATA feature allowing a drive to accept and reorder multiple outstanding requests to optimize head movement and throughput.</td><td>AHCI/SATA HDDs/SSDs improving random I/O by reordering commands.</td></tr><tr><td>NVMe</td><td>Non-Volatile Memory Express â interface protocol for SSDs over PCIe.</td><td>M.2 NVMe SSD with high IOPS/low latency.</td></tr><tr><td>RAID</td><td>Redundant Array of Independent Disks â combine multiple drives for redundancy and/or performance.</td><td>RAID 1 mirroring; RAID 5 parity; RAID 10 stripe+mirror.</td></tr><tr><td>SAS</td><td>Serial Attached SCSI â pointâtoâpoint serial interface for enterprise storage.</td><td>12Gb/s SAS HDDs/SSDs; SAS expanders/backplanes.</td></tr><tr><td>SATA</td><td>Serial ATA â interface for connecting storage devices.</td><td>2.5" SATA SSDs and HDDs.</td></tr><tr><td>SD</td><td>Secure Digital â flash memory card format with variants (SD/SDHC/SDXC) commonly used in portable devices; typically formatted with FAT32 or exFAT.</td><td>Cameras, handheld consoles, and phones; microSD cards with adapters.</td></tr><tr><td>SMART</td><td>Self-Monitoring, Analysis and Reporting Technology â monitoring system in disk drives to detect and report on indicators of drive reliability.</td><td><code>smartctl</code> to read SMART data and predict drive failure.</td></tr><tr><td>SSD</td><td>Solid-State Drive â storage device using flash memory (no moving parts), offering low latency and high throughput.</td><td>NVMe SSDs for fast boot and build times.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>EIDE</td><td>Enhanced IDE â extensions to IDE/PATA.</td><td>Support for larger drives and ATAPI.</td></tr><tr><td>IDE/PATA</td><td>Integrated Drive Electronics / Parallel ATA â legacy parallel disk interface.</td><td>40/80âwire ribbon cables for HDD/optical drives.</td></tr><tr><td>MBR</td><td>Master Boot Record â legacy partitioning scheme and first 512 bytes of a disk containing boot code and a partition table.</td><td>BIOS boots from MBR; up to 4 primary partitions or extended/logical.</td></tr><tr><td>UDMA</td><td>Ultra Direct Memory Access â ATA/IDE DMA transfer modes providing higher throughput and lower CPU usage than PIO; modes UDMA/33/66/100/133 (higher modes require 80âwire cables).</td><td>PATA drive negotiates UDMA/5 (ATA/100); Linux dmesg shows UDMA/133.</td></tr><tr><td>WORM</td><td>Write Once, Read Many â nonârewritable archival storage media.</td><td>Optical WORM jukeboxes for compliance archives.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>CHS</td><td>Cylinder/Head/Sector â legacy disk geometry addressing scheme used by BIOS/MBR era systems; limited capacity and translation quirks.</td><td>1024âcylinder limit; CHS/LBA translation in BIOS; superseded by LBA.</td></tr><tr><td>DDS</td><td>
1Digital Data Storage â magnetic tape data storage format derived from DAT (Digital Audio Tape), widely used for backups in the 1990sâ2000s (DDSâ1..4, DDSâDC, DAT72).</td><td>DAT/DDS tape drives and media for server/workstation backups; largely obsolete today.</td></tr><tr><td>DLT</td><td>Digital Linear Tape â halfâinch magnetic tape storage format popular in the 1990sâ2000s for enterprise backups; superseded by LTO.</td><td>DLT/SDLT drives and media in tape libraries; largely obsolete now.</td></tr><tr><td>FDD</td><td>Floppy Disk Drive â magnetic removable storage.</td><td>5.25" and 3.5" floppies.</td></tr><tr><td>MFM</td><td>Modified Frequency Modulation â legacy disk encoding scheme.</td><td>Early HDDs and floppies using MFM/RLL.</td></tr><tr><td>QIC</td><td>Quarter-Inch Cartridge â magnetic tape data storage format using 1/4" tape in cartridges; common for backups on PCs/workstations in the 1980sâ1990s (e.g., QIC-80/150, Travan).</td><td>Tape backup drives and cartridges; largely obsolete today.</td></tr><tr><td>RLL</td><td>Run Length Limited â denser successor to MFM for magnetic storage.</td><td>RLL controllers for higher HDD capacity.</td></tr><tr><td>SCSI</td><td>Small Computer System Interface â parallel peripheral bus widely used preâSATA/USB.</td><td>External SCSI disks and scanners on workstations.</td></tr></tbody></table><h2 id="hardware-video-displays" tabindex="-1"><a class="header-anchor" href="#hardware-video-displays"><span>Hardware (Video & Displays)</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>DP</td><td>DisplayPort â digital display interface with high bandwidth, daisyâchaining via MST, and adaptive sync support.</td><td>DP 1.4/2.0 to highârefresh monitors; USBâC DP Alt Mode; MST hub.</td></tr><tr><td>DPI</td><td>Dots Per Inch â measure of print/display resolution; colloquially used for screens though PPI is more precise.</td><td>300âDPI print quality; âRetinaâ displays around ~220 PPI.</td></tr><tr><td>EDID</td><td>Extended Display Identification Data â data structure provided by a display to describe its capabilities (e.g., resolution, timings) to a video source.</td><td>GPU reads monitor's EDID over DDC to configure the display mode.</td></tr><tr><td>GPU</td><td>Graphics Processing Unit â highly parallel processor optimized for graphics and compute.</td><td>CUDA/OpenCL workloads; 3D rendering.</td></tr><tr><td>HD</td><td>High Definition â 720p (1280Ã720) and 1080i/p (1920Ã1080) resolution classes.</td><td>1080p monitor; HD streaming.</td></tr><tr><td>HDCP</td><td>High-bandwidth Digital Content Protection â copy protection scheme to prevent copying of digital audio/video content as it travels across connections.</td><td>HDMI/DisplayPort connections requiring HDCP for protected content playback.</td></tr><tr><td>HDMI</td><td>High-Definition Multimedia Interface â digital audio/video interface for connecting sources to displays.</td><td>HDMI 2.0/2.1 to monitors/TVs; HDCP for protected content.</td></tr><tr><td>LCD</td><td>Liquid Crystal Display â flatâpanel display technology that uses liquid crystals modulated by a backlight to produce images.</td><td>IPS/TN/VA LCD panels; requires LED backlight.</td></tr><tr><td>LED</td><td>LightâEmitting Diode â semiconductor light source; in monitors/TVs, often shorthand for LEDâbacklit LCDs (not emissive perâpixel).</td><td>Status indicator LEDs; LEDâbacklit LCD monitors/TVs.</td></tr><tr><td>OLED</td><td>Organic LightâEmitting Diode â emissive display technology where each pixel emits light for high contrast and true blacks.</td><td>AMOLED smartphone screens; perâpixel dimming on TVs/phones.</td></tr><tr><td>PPI</td><td>Pixels Per Inch â measure of display pixel density; often confused with DPI which is for print.</td><td>326âPPI phone display; ~220âPPI âRetinaâ laptop panels.</td></tr><tr><td>QHD</td><td>Quad High Definition â 2560Ã1440 (1440p) resolution at 16:9; roughly 4Ã 720p and about half the pixels of 4K UHD.</td><td>27" 1440p monitors; competitive gaming displays.</td></tr><tr><td>RGB</td><td>Red, Green, Blue â additive color model used in displays and imaging.</td><td>sRGB color space; RGB LED subpixels in LCD/OLED panels.</td></tr><tr><td>RGBA</td><td>Red, Green, Blue, Alpha â RGB color with an additional alpha (opacity) channel for transparency.</td><td>CSS <code>rgba(255, 0, 0, 0.5)</code>; PNG images with alpha channel.</td></tr><tr><td>UHD</td><td>Ultra High Definition â 4K UHD (3840Ã2160) consumer resolution class; sometimes extends to 8K (7680Ã4320).</td><td>4K 2160p TV/monitor; UHD streaming.</td></tr><tr><td>VESA</td><td>Video Electronics Standards Association â industry group that defines and maintains display and related interface standards.</td><td>DisplayHDR, DP standards, EDID/DMT timing standards.</td></tr><tr><td>VRAM</td><td>Video RAM â memory used by GPUs/display controllers to store framebuffers, textures, and render targets; historically specialized types (e.g., SGRAM, GDDR).</td><td>Dedicated GDDR6 on discrete GPUs; shared system memory on iGPUs.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>SD</td><td>Standard Definition â legacy video resolution class around 480i/480p (NTSC) or 576i/576p (PAL), typically 4:3 aspect.</td><td>DVD 480p; SDTV broadcast.</td></tr><tr><td>SVGA</td><td>Super VGA â VESA extensions beyond VGA.</td><td>800Ã600 and higher resolutions.</td></tr><tr><td>VGA</td><td>Video Graphics Array â de facto PC graphics standard.</td><td>
1640Ã480 16âcolor; mode 13h 320Ã200Ã256.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>AGP</td><td>Accelerated Graphics Port â dedicated graphics slot preâPCIe.</td><td>AGP 4Ã/8Ã graphics cards.</td></tr><tr><td>CGA</td><td>Color Graphics Adapter â IBM PC color graphics standard.</td><td>320Ã200 4âcolor modes on early PCs.</td></tr><tr><td>CRT</td><td>Cathode Ray Tube â vacuum tube display technology that steers electron beams across a phosphorâcoated screen to form images.</td><td>Legacy CRT monitors/TVs; scanlines, phosphor persistence, high refresh at lower resolutions.</td></tr><tr><td>EGA</td><td>Enhanced Graphics Adapter â improved IBM graphics adapter.</td><td>640Ã350 16âcolor graphics.</td></tr><tr><td>MDA</td><td>Monochrome Display Adapter â the original text-only video card for the IBM PC.</td><td>80x25 character mode with a green or amber phosphor monitor.</td></tr></tbody></table><h2 id="hardware-general" tabindex="-1"><a class="header-anchor" href="#hardware-general"><span>Hardware (General)</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>ATX</td><td>Advanced Technology eXtended â PC motherboard and power supply form factor standard defining board sizes, mounting, I/O shield, and power connectors.</td><td>ATX/mATX/ITX cases; 24âpin ATX, 8âpin EPS12V, PCIe 6/8âpin/12VHPWR.</td></tr><tr><td>CMOS</td><td>Complementary MetalâOxideâSemiconductor â lowâpower technology used for chips; in PCs, also refers to the small batteryâbacked RAM storing firmware settings.</td><td>Replace CMOS battery; clear CMOS to reset BIOS/UEFI settings.</td></tr><tr><td>DMA</td><td>Direct Memory Access â device-initiated memory transfers without CPU involvement.</td><td>NICs use DMA for packet buffers.</td></tr><tr><td>FPGA</td><td>Field-Programmable Gate Array â reconfigurable semiconductor device consisting of programmable logic blocks and interconnects configured by a bitstream to implement custom digital circuits.</td><td>Prototype/accelerate designs; soft CPUs and hardware offload over PCIe; tools like Vivado/Quartus using HDL/RTL.</td></tr><tr><td>HID</td><td>Human Interface Device â USB device class for human input/output peripherals using structured HID reports.</td><td>USB keyboards, mice, gamepads; HID report descriptors parsed by OS.</td></tr><tr><td>HPET</td><td>High Precision Event Timer â modern hardware timer with multiple high-resolution counters/comparators, providing precise periodic interrupts and timestamps that supersede legacy PIT/RTC timers in PCs.</td><td>Program HPET registers via MMIO to drive scheduler ticks, high-resolution timers, or multimedia clocks with microsecond accuracy.</td></tr><tr><td>IRQ</td><td>Interrupt Request â a hardware signal line used by devices to interrupt the CPU for service.</td><td>Timer, keyboard, NIC raise IRQs; OS dispatches to ISRs.</td></tr><tr><td>KVM</td><td>KeyboardâVideoâMouse switch â hardware device to control multiple computers with a single keyboard, monitor, and mouse.</td><td>Toggle between two PCs with a USB/HDMI KVM switch.</td></tr><tr><td>MMIO</td><td>Memory-Mapped I/O â device registers mapped into the CPU address space for control/status.</td><td>Writing to MMIO addresses to control PCIe device registers.</td></tr><tr><td>NIC</td><td>Network Interface Controller â hardware that connects a computer to a network.</td><td>Ethernet adapters; 10/25/40/100GbE NICs with offloads.</td></tr><tr><td>OEM</td><td>Original Equipment Manufacturer â company that produces components or products that are marketed by another company; also denotes vendorâspecific builds/licenses.</td><td>OEM Windows licenses preinstalled on PCs; OEM parts used by system integrators.</td></tr><tr><td>PC</td><td>Personal Computer â general-purpose computer intended for individual use; commonly refers to IBMâPC compatible systems running Windows/Linux.</td><td>Desktop/tower PC with x86â64 CPU and discrete GPU.</td></tr><tr><td>PCH</td><td>Platform Controller Hub â the modern Intel chipset, handling I/O functions for peripherals.</td><td>The Z690 PCH provides USB, SATA, and additional PCIe lanes.</td></tr><tr><td>PSU</td><td>Power Supply Unit â converts AC mains to regulated DC rails to power computer components;
1 rated by wattage and efficiency.</td><td>ATX PSUs providing +12V/+5V/+3.3V; 80 PLUS efficiency tiers; modular cabling.</td></tr><tr><td>RTC</td><td>Real-Time Clock â hardware clock that keeps time across reboots/power cycles, often backed by a battery.</td><td>System reads RTC (CMOS/ACPI) at boot to set the OS clock.</td></tr><tr><td>SBC</td><td>Single-Board Computer â complete computer on a single circuit board integrating CPU, memory, storage, and I/O.</td><td>Raspberry Pi, BeagleBone; runs Linux for embedded/edge.</td></tr><tr><td>SIMT</td><td>Single Instruction, Multiple Threads â GPU execution model where groups of threads execute the same instruction on different data.</td><td>NVIDIA warp execution; branch divergence reduces efficiency.</td></tr><tr><td>SMBIOS</td><td>System Management BIOS â firmware tables that describe hardware to the OS.</td><td>DMI/SMBIOS tables expose model, memory, and slots.</td></tr><tr><td>SoC</td><td>System on Chip â integrated circuit that consolidates CPU cores, GPU, memory controllers, and I/O peripherals on a single die/package.</td><td>Smartphone/tablet SoCs (Apple Mâseries, Qualcomm Snapdragon); embedded ARM SoCs.</td></tr><tr><td>TPM</td><td>Trusted Platform Module â hardware-based security chip for keys and attestation.</td><td>TPM 2.0 used by Secure Boot and disk encryption.</td></tr><tr><td>VHDL</td><td>VHSIC Hardware Description Language â a hardware description language used in electronic design automation to describe digital and mixed-signal systems.</td><td>Design FPGAs and ASICs with VHDL; <code>entity</code>, <code>architecture</code>, <code>process</code>.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>PDA</td><td>Personal Digital Assistant â a handheld device that combined computing, telephone/fax, and networking features; a precursor to the smartphone.</td><td>Palm Pilot, Apple Newton, Windows CE devices.</td></tr><tr><td>PIC</td><td>Programmable Interrupt Controller â legacy interrupt controller (e.g., Intel 8259A) that routes hardware IRQs to the CPU.</td><td>Classic x86 uses dual 8259 PICs remapped during OS init.</td></tr><tr><td>PIT</td><td>Programmable Interval Timer â legacy timer chip (e.g., Intel 8253/8254) that divides a ~1.193182 MHz input clock to produce periodic interrupts for task scheduling and timekeeping.</td><td>Configure PIT channel 0 to generate IRQ0 for early OS scheduler ticks; retained as a fallback timer during boot.</td></tr></tbody></table><h2 id="firmware" tabindex="-1"><a class="header-anchor" href="#firmware"><span>Firmware</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>ACPI</td><td>Advanced Configuration and Power Interface â standard for power management and device configuration via tables provided by firmware.</td><td>ACPI tables (DSDT/SSDT) describe devices and power states to the OS.</td></tr><tr><td>AML</td><td>ACPI Machine Language â pseudo-code bytecode interpreted by the OS to evaluate ACPI objects and methods from the DSDT/SSDTs.</td><td>AML interpreter in the kernel executes methods to handle power events.</td></tr><tr><td>DSDT</td><td>Differentiated System Description Table â primary ACPI table from firmware containing the base definition of devices and power objects in AML.</td><td>The OS loads and interprets the DSDT at boot to enumerate devices.</td></tr><tr><td>FADT</td><td>Fixed ACPI Description Table â ACPI table that provides pointers to other tables and defines fixed hardware register blocks.</td><td>Contains addresses for power management timers and SCI interrupt info.</td></tr><tr><td>GRUB</td><td>GRand Unified Bootloader â a popular bootloader from the GNU project, used by most Linux distributions.</td><td>The GRUB menu for selecting an OS to boot; <code>grub.cfg</code> configuration.</td></tr><tr><td>MADT</td><td>Multiple APIC Description Table â ACPI table that describes all the interrupt controllers (APICs, IOAPICs) in the system.</td><td>The OS uses the MADT to initialize CPUs and route interrupts in an SMP system.</td></tr><tr><td>PnP</td><td>Plug and Play â automatic device detection, enumeration, and configuration by the OS/firmware, minimizing manual setup and IRQ/DMA conflicts.</td><td>ACPI/PCI PnP; USB devices enumerated and drivers autoâloaded.</td></tr><tr><td>PSCI</td><td>Power State Coordination Interface â ARM standard for power management, allowing an OS to request power state changes from system firmware.</td><td>
1OS uses PSCI calls for CPU hotplug, idle, and system shutdown.</td></tr><tr><td>RSDP</td><td>Root System Description Pointer â firmware structure that locates the main ACPI tables (RSDT/XSDT) in memory for the OS.</td><td>The OS scans for the "RSD PTR " signature in low memory to find the RSDP.</td></tr><tr><td>RSDT</td><td>Root System Description Table â 32-bit ACPI table that contains pointers to all other description tables.</td><td>Superseded by the 64-bit XSDT on modern systems.</td></tr><tr><td>SBI</td><td>Supervisor Binary Interface â standard interface between a RISCâV supervisor OS and machineâmode firmware providing services (timers, IPIs, power, console) via SBI calls; commonly implemented by OpenSBI.</td><td>Boot flow: ROM/FSBL â OpenSBI (SBI firmware) â UâBoot/Linux; OS issues <code>ecall</code> to SBI for privileged services.</td></tr><tr><td>SCI</td><td>System Control Interrupt â a dedicated interrupt used by ACPI to signal power management and other system events to the OS.</td><td>ACPI SCI handler for lid open/close or power button events.</td></tr><tr><td>SMI</td><td>System Management Interrupt â a high-priority interrupt that causes the CPU to enter System Management Mode (SMM).</td><td>Triggered by hardware or firmware to handle platform-specific events.</td></tr><tr><td>SMM</td><td>System Management Mode â a special-purpose CPU mode in x86 for handling system-wide functions like power management and proprietary OEM code, transparent to the OS.</td><td>SMI handler for power button events; legacy USB keyboard emulation.</td></tr><tr><td>SSDT</td><td>Secondary System Description Table â additional ACPI tables containing AML definitions that supplement or modify the DSDT.</td><td>Used for device-specific configuration or hot-plug support.</td></tr><tr><td>UEFI</td><td>Unified Extensible Firmware Interface â modern firmware replacing legacy BIOS with a flexible boot and runtime services model.</td><td>UEFI boot managers, GPT disks, Secure Boot.</td></tr><tr><td>XSDT</td><td>Extended System Description Table â 64-bit version of the RSDT that contains pointers to all other ACPI description tables.</td><td>Used by modern 64-bit operating systems to find ACPI tables.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>CSM</td><td>Compatibility Support Module â UEFI component that provides legacy BIOS services to boot nonâUEFI OSes and option ROMs; phased out on modern systems.</td><td>Enable CSM to boot legacy MBR media or old GPUs with legacy option ROMs.</td></tr><tr><td colspan="3"><strong>Historical</strong></td></tr><tr><td>APM</td><td>Advanced Power Management â legacy firmware interface for power management, superseded by ACPI.</td><td>APM BIOS calls for sleep/shutdown on pre-ACPI systems.</td></tr><tr><td>BIOS</td><td>Basic Input/Output System â legacy PC firmware that initializes hardware and boots the OS.</td><td>PC firmware POST and boot sequence on legacy/CSM systems.</td></tr><tr><td>POST</td><td>Power-On Self-Test â diagnostic sequence run by firmware (esp. legacy BIOS) at startup to check hardware integrity.</td><td>Beep codes on failure; memory/drive checks during boot.</td></tr></tbody></table><h2 id="culture-misc" tabindex="-1"><a class="header-anchor" href="#culture-misc"><span>Culture & Misc</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AFAICT</td><td>As Far As I Can Tell â based on current understanding.</td><td>âAFAICT, the bug only affects Safari.â</td></tr><tr><td>AFAIK</td><td>As Far As I Know â indicates incomplete knowledge.</td><td>âAFAIK, we don't support Windows 7 anymore.â</td></tr><tr><td>AFK</td><td>Away From Keyboard â temporarily unavailable.</td><td>âAFK 10 mins, brb.â</td></tr><tr><td>ASAP</td><td>As Soon As Possible â urgent request or prioritization; avoid ambiguity by specifying a concrete timeframe when possible.</td><td>âPlease review ASAPâ â âPlease review by EOD.â</td></tr><tr><td>ATM</td><td>At The Moment â current status may change.</td><td>âATM we're blocked on upstream changes.â</td></tr><tr><td>BDFL</td><td>Benevolent Dictator For Life â long-term project leader.</td><td>Pythonâs BDFL history.</td></tr><tr><td>BOFH</td><td>Bastard Operator From Hell â cynical sysadmin trope.</td><td>Humor in ops culture.</td></tr><tr><td>BRB</td><td>Be Right Back â brief step away.</td><td>âBRB, grabbing coffee.â</td></tr><tr><td>BTW</td><td>By The Way â add side note/context.</td><td>âBTW, the API changed in v2.â</td></tr><tr><td>DM</td><td>Direct Message â private one-to-one message in chat/social platforms.</td><td>âSend me a DM with the logs.â</td></tr><tr><td>ELI5</td><td>Explain Like I'm Five â request for simple explanation.</td><td>âELI5 how RSA works.â</td></tr><tr><td>EOD</td><td>End Of Day â end of a working day; common deadline shorthand.</td><td>âI'll have a draft ready by EOD.â</td></tr><tr><td>EOW</td><td>End Of Week â end of the current work week; deadline shorthand.</td><td>âTargeting EOW for the feature toggle rollout.â</td></tr><tr><td>
1EOY</td><td>End Of Year â end of the calendar or fiscal year; deadline shorthand.</td><td>âLet's target EOY for GA after extended beta.â</td></tr><tr><td>ETA</td><td>Estimated Time of Arrival â expected completion/arrival time.</td><td>âETA for fix is 3pm.â</td></tr><tr><td>FFS</td><td>For F***'s Sake â expression of frustration or exasperation; avoid in formal communication.</td><td>âFFS, the build broke again.â</td></tr><tr><td>FOMO</td><td>Fear Of Missing Out â anxiety about missing experiences or opportunities others are having.</td><td>âSkip the release party? FOMO is real.â</td></tr><tr><td>FTW</td><td>For The Win â enthusiastic endorsement or celebration of something that worked well.</td><td>âFeature flags FTW â painless rollback.â</td></tr><tr><td>FUD</td><td>Fear, Uncertainty, Doubt â disinformation tactic.</td><td>Competitor FUD.</td></tr><tr><td>FWIW</td><td>For What It's Worth â modest preface to share input without asserting authority.</td><td>âFWIW, retry with exponential backoff.â</td></tr><tr><td>FYI</td><td>For Your Information â share info without requiring action.</td><td>âFYI: maintenance window Sunday 2am.â</td></tr><tr><td>GTK</td><td>Good To Know â acknowledges helpful info.</td><td>âRate limit resets hourly â GTK.â</td></tr><tr><td>HN</td><td>Hacker News â tech news and discussion site run by Y Combinator.</td><td>Post a launch on news.ycombinator.com; join the discussion.</td></tr><tr><td>HTH</td><td>Hope This Helps â friendly signâoff when providing assistance or an answer.</td><td>âHTH! Ping me if you need more details.â</td></tr><tr><td>ICYMI</td><td>In Case You Missed It â pointer to noteworthy info shared earlier.</td><td>âICYMI, the outage postmortem is posted.â</td></tr><tr><td>IDK</td><td>I Don't Know â lack of information.</td><td>âIDK the root cause yet; investigating.â</td></tr><tr><td>IIRC</td><td>If I Recall Correctly â hedged memory.</td><td>âIIRC, that was fixed in 1.2.â</td></tr><tr><td>IIUC</td><td>If I Understand Correctly â confirm interpretation.</td><td>âIIUC, only a config change is needed.â</td></tr><tr><td>IMHO</td><td>In My Humble Opinion â opinion preface.</td><td>âIMHO, we should simplify.â</td></tr><tr><td>IMO</td><td>In My Opinion â opinion preface; a slightly less self-deprecating variant of IMHO.</td><td>âIMO, we should ship featureâflagged.â</td></tr><tr><td>IRL</td><td>In Real Life â referring to the physical/offline world as opposed to online/virtual contexts.</td><td>âLet's meet IRL next week.â</td></tr><tr><td>LGTM</td><td>Looks Good To Me â code review approval.</td><td>âLGTM, ship it.â</td></tr><tr><td>LMGTFY</td><td>Let Me Google That For You â snarky suggestion to search the web first; use sparingly as it can come across as dismissive.</td><td>âLMGTFY: how to clear npm cache.â</td></tr><tr><td>LMK</td><td>Let Me Know â request a follow-up.</td><td>âLMK if the deploy finishes.â</td></tr><tr><td>MAME</td><td>Multiple Arcade Machine Emulator â a free and open-source emulator designed to recreate the hardware of arcade game systems in software.</td><td>Preserve gaming history by playing classic arcade games with MAME.</td></tr><tr><td>MOTD</td><td>Message Of The Day â login banner/notice.</td><td><code>/etc/motd</code> on login.</td></tr><tr><td>NBD</td><td>No Big Deal â indicates something is minor or not worth worrying about.</td><td>âMissed the standup â NBD.â</td></tr><tr><td>NIH</td><td>Not Invented Here â bias to build your own instead of using existing solutions.</td><td>Replacing a mature library with custom code.</td></tr><tr><td>NP</td><td>No Problem â acknowledgment that a request is fine or a task is acceptable.</td><td>âNP, I can take this.â</td></tr><tr><td>NSFW</td><td>Not Safe For Work â content that may be inappropriate for professional settings.</td><td>âNSFW: explicit language/images; open privately.â</td></tr><tr><td>OOO</td><td>Out Of Office â unavailable for work/response.</td><td>âOOO until Monday.â</td></tr><tr><td>OP</td><td>Original Poster â thread/issue creator.</td><td>âPer OPâs repro steps â¦â</td></tr><tr><td>OT</td><td>Off Topic â content not related to the main subject/thread.</td><td>âOT: anyone tried the new keyboard switches?â</td></tr><tr><td>OTOH</td><td>On The Other Hand â introduces a contrasting point or alternative perspective.</td><td>âWe can optimize now; OTOH, premature optimization adds risk.â</td></tr><tr><td>PEBKAC</td><td>Problem Exists Between Keyboard And Chair â user error.</td><td>Misconfigured client settings.</td></tr><tr><td>PITA</td><td>Pain In The Ass â something annoying or cumbersome; avoid in formal communication.</td><td>âThat migration was a PITA.â</td></tr><tr><td>PTO</td><td>Paid Time Off â time away from work.</td><td>âOn PTO next week.â</td></tr><tr><td>QQ</td><td>Quick Question â brief, lowâeffort question or nudge for a short answer.</td><td>
1âQQ: is staging using the new DB URL?â</td></tr><tr><td>RIP</td><td>Rest In Peace â tongue-in-cheek epitaph for a feature, service, or idea that just failed or was deprecated.</td><td>âRIP staging cluster after that migration.â</td></tr><tr><td>RPG</td><td>Role-Playing Game â a game in which players assume the roles of characters in a fictional setting.</td><td>Tabletop RPGs like D&D; computer RPGs like Final Fantasy.</td></tr><tr><td>RTFM</td><td>Read The F***ing Manual â read docs first.</td><td><code>git rebase --help</code>.</td></tr><tr><td>SME</td><td>Subject-Matter Expert â domain expert.</td><td>Security SME review.</td></tr><tr><td>SMH</td><td>Shaking My Head â expresses disappointment or disbelief.</td><td>âProd creds in a script? SMH.â</td></tr><tr><td>SO</td><td>Stack Overflow â popular Q&A site for programming and software development.</td><td>Link to an accepted SO answer for a solution/workaround.</td></tr><tr><td>TANSTAAFL</td><td>There Ain't No Such Thing As A Free Lunch â highlights that every choice has tradeâoffs or hidden costs; nothing is truly free.</td><td>âTANSTAAFL: caching speeds reads but adds complexity/invalidation.â</td></tr><tr><td>TBA</td><td>To Be Announced â details later.</td><td>Rollout date TBA.</td></tr><tr><td>TBD</td><td>To Be Determined â not finalized.</td><td>Owner TBD after planning.</td></tr><tr><td>TBH</td><td>To Be Honest â candid preface.</td><td>âTBH, refactor first.â</td></tr><tr><td>TFA</td><td>The F***ing Article â read the article.</td><td>TFA explains REST vs RPC.</td></tr><tr><td>TIA</td><td>Thanks In Advance â polite signâoff indicating appreciation for help to come; consider whether it pressures recipients.</td><td>âTIA for reviewing the PR.â</td></tr><tr><td>TIL</td><td>Today I Learned â sharing a new fact or insight just learned.</td><td>âTIL <code>git worktree</code> simplifies multi-branch checkouts.â</td></tr><tr><td>TL;DR</td><td>Too Long; Didn't Read â summary.</td><td>TL;DR: Use approach B.</td></tr><tr><td>TLA</td><td>Three-Letter Acronym â meta-acronym.</td><td>âAnother TLA.â</td></tr><tr><td>TTYL</td><td>Talk To You Later â casual sign-off indicating youâll continue the conversation later.</td><td>âGotta run â TTYL.â</td></tr><tr><td>WCGW</td><td>What Could Go Wrong â tongue-in-cheek before risk.</td><td>âDeploy Friday, WCGW?â</td></tr><tr><td>WFH</td><td>Work From Home â remote from home.</td><td>âWFH today.â</td></tr><tr><td>WTF</td><td>What The F*** â expression of surprise, confusion, or frustration; avoid in formal communication.</td><td>âWTF happened to the build pipeline?â</td></tr><tr><td>YMMV</td><td>Your Mileage May Vary â results differ.</td><td>Different env outcomes.</td></tr><tr><td>YOLO</td><td>You Only Live Once â humorously justifies taking a risk; use with care.</td><td>"YOLO deploy" on Friday â probably don't.</td></tr><tr><td colspan="3"><strong>Legacy</strong></td></tr><tr><td>MUD</td><td>Multi-User Dungeon â a text-based, online multiplayer role-playing game; a precursor to MMORPGs.</td><td>Connect via Telnet; DikuMUD, LPMud, MUSH/MUCK/MOO variants.</td></tr></tbody></table><h2 id="organizations" tabindex="-1"><a class="header-anchor" href="#organizations"><span>Organizations</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>ACM</td><td>Association for Computing Machinery â international learned society for computing, publishing journals, conferences, curricula, and best practices.</td><td>ACM SIGs (SIGGRAPH, SIGPLAN), ACM Digital Library, Turing Award.</td></tr><tr><td>ANSI</td><td>American National Standards Institute â U.S. standards organization that oversees and coordinates standards development and accredits standards bodies.</td><td>ANSI C (C89/C90) standardization; coordinates U.S. positions in ISO/IEC JTC 1.</td></tr><tr><td>ASF</td><td>Apache Software Foundation â nonâprofit that supports Apache open source projects and communities.</td><td>Apache HTTP Server, Hadoop, Kafka, Spark under the ASF.</td></tr><tr><td>BBN</td><td>Bolt Beranek and Newman â pioneering research and engineering firm (now BBN Technologies) that built the ARPANET IMPs, advanced routing research, and contributed foundational internet and defense networking work.</td><td>BBN designed ARPANET IMPs, hosted early TCP/IP research, and continued DARPA-funded networking projects.</td></tr><tr><td>
1CNCF</td><td>Cloud Native Computing Foundation â part of the Linux Foundation hosting cloudânative projects and standards.</td><td>Kubernetes, Prometheus, Envoy; CNCF landscape and graduation levels.</td></tr><tr><td>ECMA</td><td>Ecma International â industry association for information and communication systems standards.</td><td>ECMAScript (JavaScript), C# (ECMA-334), CLI (ECMA-335).</td></tr><tr><td>EFF</td><td>Electronic Frontier Foundation â a non-profit organization defending civil liberties in the digital world.</td><td>Advocates for privacy, free speech, and innovation online.</td></tr><tr><td>FSF</td><td>Free Software Foundation â GNU/GPL steward.</td><td>Publishes GPL family.</td></tr><tr><td>GNU</td><td>GNUâs Not Unix â FSF project and philosophy.</td><td>GNU toolchain/userland.</td></tr><tr><td>IANA</td><td>Internet Assigned Numbers Authority â coordinates global IP addressing, DNS root zone management (with ICANN), and protocol parameter registries (ports, DHCP options, etc.).</td><td>Port numbers and protocol parameters registries; root zone management with ICANN.</td></tr><tr><td>NIC</td><td>Network Information Center â organization responsible for domain registration, IP allocation, and directory services in early networks; historically includes SRI-NIC (ARPANET) and national NICs.</td><td>SRI's NIC handled ARPANET hostnames and RFC distribution; modern NICs manage ccTLDs (e.g., RIPE NCC, AFRINIC roles).</td></tr><tr><td>ICANN</td><td>Internet Corporation for Assigned Names and Numbers â oversees the global DNS root, IP address allocation policy coordination, and domain name registries/registrars.</td><td>gTLD/ccTLD policies; WHOIS/RDAP; root zone stewardship.</td></tr><tr><td>IEEE</td><td>Institute of Electrical and Electronics Engineers â professional association and standards body producing technical standards.</td><td>IEEE 802 (Ethernet/WiâFi), IEEE 754 floatingâpoint.</td></tr><tr><td>IETF</td><td>Internet Engineering Task Force â open standards body that develops and publishes internet standards as RFCs.</td><td>HTTP/1.1 (RFC 723x), TLS (RFC 8446), QUIC (RFC 9000); working groups and I-Ds.</td></tr><tr><td>ISO</td><td>International Organization for Standardization â independent, nonâgovernmental international standards body.</td><td>ISO 8601 dates/times; ISO/IEC 9899 (C), ISO/IEC 14882 (C++).</td></tr><tr><td>ITUâT</td><td>International Telecommunication Union â Telecommunication Standardization Sector; develops telecom standards (Recommendations) for networks, media, and services.</td><td>ITUâT H.264/H.265 (with ISO/IEC), G.711/G.722 codecs; numbering, signaling, and transport Recs.</td></tr><tr><td>NIST</td><td>National Institute of Standards and Technology â U.S. federal agency that develops standards, guidelines, and measurements to improve technology, cybersecurity, and commerce.</td><td>NIST SP 800â53/63/171 security guidelines; NIST hash/SHA competition; time services.</td></tr><tr><td>OASIS</td><td>OASIS Open â consortium that develops open standards for security, identity, content, and more.</td><td>SAML, STIX/TAXII, KMIP; technical committees and OASIS specifications.</td></tr><tr><td>OMG</td><td>Object Management Group â consortium that develops technology standards, notably modeling/specification standards.</td><td>UML, CORBA, BPMN standards; working groups and specifications.</td></tr><tr><td>OSI</td><td>Open Source Initiative â OSI-approved licenses.</td><td>Open Source Definition stewardship.</td></tr><tr><td>OWASP</td><td>Open Web Application Security Project â a non-profit foundation focused on improving software security.</td><td>The OWASP Top 10 list of critical web application security risks; OWASP ZAP scanner.</td></tr><tr><td>PARC</td><td>Palo Alto Research Center (formerly Xerox PARC) â famed industrial research lab that pioneered modern computing breakthroughs in GUIs, Ethernet, laser printing, and object-oriented systems.</td><td>PARC's Alto workstation, Smalltalk environment, and Ethernet prototypes seeded foundational ideas adopted across the industry.</td></tr><tr><td>PCI-SIG</td><td>Peripheral Component Interconnect Special Interest Group â consortium that develops and maintains PCI and PCI Express specifications and compliance programs.</td><td>
1PCIe 5.0/6.0 specs, CEM/ECNs; compliance workshops and device interoperability testing.</td></tr><tr><td>SPEC</td><td>Standard Performance Evaluation Corporation â develops industryâstandard benchmarks for computing performance and energy.</td><td>SPEC CPU, SPECjbb, SPECpower; widely cited performance metrics.</td></tr><tr><td>TPC</td><td>Transaction Processing Performance Council â benchmarks for database and transaction processing systems.</td><td>TPCâC (OLTP), TPCâH/TPCâDS (analytics), audited results and full disclosure reports.</td></tr><tr><td>W3C</td><td>World Wide Web Consortium â standards body that develops web specifications and recommendations.</td><td>HTML/CSS/DOM specs; Working Groups and drafts at w3.org.</td></tr><tr><td>WHATWG</td><td>Web Hypertext Application Technology Working Group â community maintaining living standards for HTML, DOM, and related web platform technologies.</td><td>HTML Living Standard; DOM and URL standards coâdeveloped with browsers.</td></tr></tbody></table><h2 id="licensing-open-source" tabindex="-1"><a class="header-anchor" href="#licensing-open-source"><span>Licensing & Open Source</span></a></h2><table><thead><tr><th>Acronym</th><th>Meaning</th><th>Example</th></tr></thead><tbody><tr><td>AGPL</td><td>GNU Affero GPL â copyleft with network-use clause.</td><td>SaaS must release source of modifications.</td></tr><tr><td>BSD</td><td>Berkeley Software Distribution â permissive license family.</td><td>BSD-2, BSD-3 clause variants.</td></tr><tr><td>EULA</td><td>End-User License Agreement â contract between software provider and end user defining usage rights/restrictions; common for proprietary software.</td><td>Accept EULA during installation; governs redistribution and usage.</td></tr><tr><td>FLOSS</td><td>Free/Libre and Open Source Software â umbrella term.</td><td>General discussions of FLOSS.</td></tr><tr><td>FOSS</td><td>Free and Open Source Software â umbrella term.</td><td>FOSS projects and communities.</td></tr><tr><td>GPL</td><td>GNU General Public License â strong copyleft.</td><td>Derivatives must remain open.</td></tr><tr><td>LGPL</td><td>GNU Lesser GPL â weak copyleft for linking.</td><td>Use in libraries linkable from proprietary apps.</td></tr><tr><td>MIT</td><td>MIT License â simple permissive license.</td><td>Many JS libs under MIT.</td></tr><tr><td>OSS</td><td>Open Source Software â software under OSI licenses.</td><td>OSS adoption.</td></tr></tbody></table></div>',4)]))}const c=e(o,[["render",n],["__file","index.html.vue"]]),l=JSON.parse('{"path":"/acronyms/","title":"Computing Acronyms","lang":"en-US","frontmatter":{"title":"Computing Acronyms","sidebarDepth":1},"headers":[{"level":2,"title":"Software Architecture","slug":"softw
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