Uncategorized
Coordinated Universal Time (UTC)
UTC is the primary time standard by which the world regulates clocks and time. It is derived from International Atomic Time (TAI) with leap seconds added to stay aligned with Earth's rotation.
JSON
JavaScript Object Notation — a lightweight, text-based data interchange format derived from a subset of JavaScript syntax, standardized as ECMA-404 and RFC 8259.
HTTP
The Hypertext Transfer Protocol (HTTP) is the application-layer protocol that underlies the World Wide Web. Clients send method-based requests (GET, POST, PUT, DELETE, HEAD, etc.) over TCP or QUIC, and servers reply with a status code, headers, and an optional body. HTTP/1.1 remains widely deployed, with HTTP/2 multiplexing and HTTP/3 over QUIC layering performance improvements on the same semantic model.
Public Goods in Economics
A public good in economics is defined by two properties — non-rivalry and non-excludability — formalized by Paul Samuelson's 1954 paper 'The Pure Theory of Public Expenditure'. Classic examples include clean air, national defense, lighthouses, and freely accessible knowledge. Because users cannot be excluded, public goods suffer from the free-rider problem and tend to be underprovided by markets, typically requiring government, philanthropy, or voluntary collective action.
SHA-256
SHA-256 is a cryptographic hash function in the SHA-2 family that produces a 256-bit digest. Designed by the NSA and published by NIST in 2001, it is widely used for digital signatures, blockchain proof-of-work, TLS certificates, and content addressing.
Git (version control)
Git is a distributed version control system created by Linus Torvalds in 2005 for Linux kernel development. It models a repository as a content-addressed object database — blobs, trees, commits, and tags — identified by cryptographic hash.
ANSI Escape Sequences: Terminal Colors and Cursor Control
ANSI escape sequences are in-band control codes — standardized by ECMA-48 in 1976 — that terminals interpret to set colors, move the cursor, and clear the screen. The Control Sequence Introducer (CSI = ESC [, bytes 0x1B 0x5B) starts most commands. SGR sequences ending in 'm' control colors: 3/4-bit (16 base), 8-bit (256 palette), and 24-bit truecolor (ESC [38;2;R;G;Bm). Windows ignored them until version 1511 in 2016. Writing escapes to a non-tty stream corrupts log files, so well-behaved tools check isatty() first.
Unix File Permissions Decoded
Unix permissions pack into 12 bits: nine for owner/group/other rwx plus three for setuid, setgid, and the sticky bit, displayed as four octal digits. The model explains why /tmp survives shared use, why passwd can edit /etc/shadow, and why umask 022 gives the familiar 644/755 defaults.
Vixie Cron
The reference implementation of {{Unix cron}} written by Paul Vixie in 1987 and the basis of nearly every modern Linux and BSD cron daemon.
Bash (Shell)
GNU Bourne-Again SHell, first released June 8, 1989 by {{Brian Fox}} for the {{GNU Project}} as a free-software replacement for the {{Bourne shell}}; the default login shell on most Linux distributions and, historically, on macOS, maintained since 1990 by {{Chet Ramey}}.
POSIX ACL
POSIX ACLs extend Unix's owner/group/other model with per-user and per-group entries stored as extended attributes. Managed with setfacl and getfacl, they are supported by ext4, XFS, Btrfs, and others, and shown by a trailing + in ls -l.
ECMA-48
ECMA-48 is the 1976 European standard 'Control Functions for Coded Character Sets' that defines the escape sequences terminals interpret for cursor movement, screen erasure, and colors. Aligned with ANSI X3.64 (1979) and ISO/IEC 6429 (1983), it specifies the Control Sequence Introducer (ESC [ or 0x9B) plus the parameter grammar — most famously SGR for colors and attributes. The 5th edition (1991) is the current revision and remains the canonical reference for terminal emulator authors.
Useful Bash Parameter Expansion Patterns
Reference for the high-value forms of {{Bash parameter expansion}}: default values, length, prefix/suffix stripping (greedy and non-greedy), pattern substitution, substring slicing, and case modification. The ${var...} syntax that nobody remembers cold but everyone Googles.
umask
umask is a per-process mask on Unix that clears permission bits from newly created files and directories. The common 022 value yields 644 files and 755 directories; tighter sites use 027 or 077.
Setuid
Setuid is a Unix permission bit (octal 4000) that makes an executable run with the file owner's effective UID rather than the caller's. It powers passwd, sudo, and ping, and is a perennial privilege-escalation surface.
Sticky Bit
The sticky bit (octal 1000) once asked the kernel to keep an executable's text in swap. Its surviving use is on directories like /tmp: it restricts deletion of files inside to each file's owner, making world-writable scratch space safe.
401 Unauthorized vs 403 Forbidden
401 means the request lacks valid authentication; 403 means the caller is authenticated but not permitted. RFC 9110 makes the distinction explicit and requires a WWW-Authenticate header on 401.
seL4 (Microkernel)
seL4 is a member of the L4 microkernel family that in 2009 became the first general-purpose operating-system kernel with a machine-checked proof of functional correctness against its specification. Developed at NICTA in Sydney by a team led by Gerwin Klein, Kevin Elphinstone, and Gernot Heiser, it is open source under GPLv2 and is used in high-assurance avionics, defence, automotive, and IoT systems.
SMTP (Simple Mail Transfer Protocol)
Text-based protocol for relaying email between {{Mail Transfer Agent}}s, originally specified by {{Jon Postel}} in RFC 821 (August 1982) alongside {{RFC 822}}, and updated to RFC 5321 in 2008; it carries the message envelope while RFC 5322 governs the message content.
WHATWG
The Web Hypertext Application Technology Working Group, founded 4 June 2004 by Apple, Mozilla, and Opera after W3C rejected a pragmatic HTML extension proposal. WHATWG's principles — backwards compatibility, specified error recovery, and continuous evolution — produced HTML5 and the Living Standard model. Since 2019 it is the sole publisher of HTML and DOM standards.
x86-64
AMD's backwards-compatible 64-bit extension of the x86 instruction set, announced 1999, first shipped in Opteron (2003), later adopted by Intel as EM64T / Intel 64. The dominant 64-bit ISA for PCs and a leading one for servers.
HTML5
The fifth major version of HTML, originating as WHATWG's Web Applications 1.0 draft and adopted by the W3C in 2007. Reached Recommendation status in 2014. Designed for backwards compatibility, precisely specified error recovery, and a large feature surface (video, canvas, semantic elements, offline storage). Stewardship passed entirely to WHATWG in 2019 as the HTML Living Standard.
Tanenbaum-Torvalds Debate
A 1992 Usenet exchange in comp.os.minix between Andrew Tanenbaum, creator of Minix, and Linus Torvalds, creator of Linux, over whether monolithic kernels like Linux were obsolete compared to microkernel designs. The debate became a touchstone for the broader microkernel-versus-monolithic argument and is widely re-read today as a study in how engineering pragmatism beat architectural aesthetics.
Base64 Encoding
Binary-to-text encoding that maps every 3 input bytes (24 bits) to 4 printable ASCII characters drawn from a 64-character alphabet, used by {{MIME}} to carry binary data through 7-bit-clean mail transports and widely reused for embedding small blobs in JSON, URLs, and HTTP headers.
ECMAScript
The official standardized specification of the {{JavaScript}} language, maintained by {{Ecma International}} as standard ECMA-262 and developed by the {{TC39}} committee.
REST API
An API style built on the constraints of Representational State Transfer, using stateless HTTP requests, resource-oriented URLs, and standard verbs to manipulate representations of resources.
Daylight Saving Time
Daylight Saving Time (DST) is the practice of advancing civil clocks, usually by one hour, during warmer months to shift daylight from morning to evening. Adoption, dates, and offsets vary widely by country and have changed repeatedly through history.
Brendan Eich
American programmer best known for creating {{JavaScript}} in ten days at {{Netscape}} in May 1995, co-founding the Mozilla project in 1998, and later co-founding Brave Software.
IANA
The Internet Assigned Numbers Authority (IANA) coordinates global allocation of internet number resources, root DNS, protocol parameters, and the tz time zone database. It operates under ICANN.
XML
Extensible Markup Language — a W3C-standardized markup format with named tags, attributes, and namespaces, designed in the late 1990s for self-describing, human-readable structured data interchange.
Subword Tokenization
Subword tokenization splits text into pieces smaller than words but larger than characters. It solves the open-vocabulary problem for neural language models and is the dominant approach in modern LLMs, with BPE, WordPiece, and Unigram as the main algorithm families.
Byte-Pair Encoding (BPE)
Byte-Pair Encoding is a subword tokenization algorithm that learns a vocabulary by iteratively merging the most frequent adjacent symbol pairs in a corpus. Originally a 1994 compression trick, it became the dominant tokenization method for GPT, LLaMA, and most modern LLMs after a 2016 NLP adaptation.
SentencePiece
SentencePiece is an open-source tokenizer library from Google that trains subword models directly on raw text, without language-specific pre-tokenization. It supports both BPE and Unigram algorithms and underpins LLaMA, T5, mT5, and Google's Gemini family.
Brooks's Law
Software project management aphorism coined by Fred Brooks in The Mythical Man-Month (1975): adding manpower to a late software project makes it later. Captures the diseconomies of scale in coordinating large engineering teams.
Shellshock (Bash vulnerability)
Family of 2014 vulnerabilities in GNU Bash allowing remote code execution by smuggling commands through specially crafted environment variables. The original bug had been latent in Bash for roughly 25 years before discovery.
Wikimedia Foundation
American nonprofit incorporated in 2003 to host and support Wikipedia and its sister free-knowledge projects, including Wiktionary, Wikimedia Commons, and Wikidata. Funded mainly through small donations and grants.
Wikidata
Free, multilingual, machine-readable knowledge base launched by the Wikimedia Foundation in October 2012. Organizes facts as items (QIDs) and properties (P-prefixed), exposed via a SPARQL endpoint, released under CC0, and consumed by Wikipedia infoboxes, search engines, and virtual assistants.
Heartbleed
Critical 2014 vulnerability in OpenSSL's TLS heartbeat extension that allowed remote attackers to read up to 64 KB of process memory per request, leaking private keys, session tokens, and passwords from a large fraction of the public web.
GitHub
The largest hosted Git repository service, central to open-source collaboration since 2008 and owned by Microsoft since 2018.
Goodhart's Law
Goodhart's Law observes that when a measure becomes a target, it ceases to be a good measure. Originally a remark by economist Charles Goodhart about monetary policy, it now describes gaming behavior across metrics, ML reward functions, school testing, and academic citation counts.
Budapest Open Access Initiative
The Budapest Open Access Initiative (BOAI), released February 14, 2002, is the founding declaration of the {{Open Access}} movement. Convened by the Open Society Institute in December 2001, it defined OA, distinguished 'gratis' from 'libre' access, and named self-archiving plus OA journals as the two core strategies.
Citation Needed
Wikipedia's [citation needed] tag, introduced in 2006, marks unsourced claims as public IOUs and operationalizes the project's verifiability policy. As of mid-2025 it appeared on more than 604,000 pages.
Creative Commons Licensing
Creative Commons is a family of standardized public copyright licenses launched in 2002 by a U.S. nonprofit co-founded by Lawrence Lessig. Six core licenses are built from four interchangeable elements (BY, SA, NC, ND), with CC0 added in 2009 as a public-domain dedication. The system underpins large parts of the open commons (Wikipedia, OpenStreetMap, Stack Overflow, MIT OpenCourseWare) but carries known tradeoffs: SA is virally copyleft, NC has chronically ambiguous scope, and ND blocks remixing.
arXiv
arXiv is the dominant {{preprint}} server for physics, mathematics, computer science, and adjacent fields. Founded in August 1991 by physicist Paul Ginsparg at Los Alamos and now hosted at Cornell, it functions as a free repository where researchers post manuscripts before, alongside, or instead of formal journal publication.
Preprint
A preprint is a version of a scholarly paper shared publicly before formal peer review and journal publication. Preprint servers such as {{arXiv}}, bioRxiv, medRxiv, and SSRN let researchers establish priority, gather feedback, and disseminate results quickly. The model is central to {{Green Open Access}} and surged in visibility during COVID-19.
Elinor Ostrom
American political scientist (1933-2012) whose empirical work on community-managed commons earned her the 2009 Nobel Memorial Prize in Economic Sciences — the first awarded to a woman. Her book Governing the Commons offered a systematic rebuttal to Garrett Hardin's pessimism.
Ostrom's Design Principles for Commons
Elinor Ostrom's eight design principles, from Governing the Commons (1990), describe institutional features common to long-lived self-governing commons: clear boundaries, locally fitted rules, collective-choice participation, accountable monitoring, graduated sanctions, cheap conflict resolution, recognized right to organize, and nested enterprises. The framework rebutted Hardin's tragedy of the commons by showing communities can sustainably manage shared resources without privatization or top-down control, and Hess & Ostrom (2007) extended it to knowledge commons.
Tragedy of the Commons
The tragedy of the commons is a metaphor for how rational individual use of a shared, unmanaged resource can lead to its collective ruin. Popularized by ecologist Garrett Hardin in a 1968 Science paper, the framing has shaped environmental and economic policy for decades — though Elinor Ostrom's later empirical work showed real communities often govern commons successfully without privatization or external coercion.
Common-Pool Resources
Common-pool resources are rival but non-excludable: one user's consumption reduces what is available to others, yet excluding additional users is costly or impossible. Examples include fisheries, groundwater, forests, and the atmosphere. Elinor Ostrom's work showed that local institutions can manage them sustainably without privatization or state control.
Club Goods
Club goods are excludable but non-rival: access can be restricted, but one user's consumption does not reduce availability for others. The category was introduced by James Buchanan in his 1965 paper 'An Economic Theory of Clubs' to fill the gap between purely private and purely public goods.