Technology

Package management system A package management system automates installing, upgrading, configuring and removing software packages, tracking files, resolving dependencies and managing repositories for reliab…

Padlock: portable lock types, design, uses, history and security Padlock Overview of padlocks: portable locks with a U-shaped shackle. Covers construction, types, history, common uses, vulnerabilities, security features, selection and maintenance guidan…

Page cache: in-memory caching of file data in virtual memory systems Page cache The page cache stores recently used file contents in RAM as memory pages. It reduces disk I/O, supports memory-mapped files, and is implemented in modern kernels as a unified cache…

Page Replacement Algorithms in Virtual Memory Systems Page replacement algorithm A concise guide to page replacement algorithms: what they are, common strategies (LRU, FIFO, Clock, etc.), history, and practical trade-offs in operating systems and applications.

Palm OS — operating system for PDAs and early mobile devices Palm OS Palm OS is a lightweight operating system designed for personal digital assistants and early smartphones, known for its simple GUI, Graffiti handwriting input, HotSync synchronizat…

Panasonic Q A premium variant of the Nintendo GameCube produced by Panasonic that combined GameCube game compatibility with DVD playback; released exclusively in Japan in 2001 and prized by co…

Paparazzi Project — open-source autopilot system for micro-UAVs Paparazzi Project Paparazzi is a community-driven, open-source autopilot and ground station system for small unmanned aircraft. It emphasizes modular hardware, flexible software and low-cost DIY use…

Paper clip Small bent-wire or plastic fastener used to hold sheets of paper together temporarily; known for the Gem design, many variants, simple spring-action principle, and wide practical a…

Paper mill Industrial plant that converts wood and plant fibers into paper by pulping, forming, pressing, drying and finishing. Covers raw materials, processes, products, history and environm…

Paper towel Disposable absorbent sheets made from paper fibers, used for cleaning, drying and hygiene; produced in rolls or sheets and notable for absorbency, convenience and environmental tra…

Parabolic Trough: Concentrating Solar Thermal Collector and Its Uses Parabolic trough A parabolic trough is a linear concentrating solar collector that focuses sunlight onto a receiver tube to produce high-temperature heat for electricity generation, industrial heat…

Parallel ATA (PATA): legacy parallel storage interface for PCs Parallel ATA Parallel ATA (PATA) is a legacy parallel interface for connecting internal storage devices in personal computers. It evolved from IDE/ATA, later branded PATA after Serial ATA's int…

Parallel computing: concepts, forms, programming challenges, and uses Parallel computing Overview of parallel computing: definition, main types and hardware levels, historical drivers, programming challenges, common uses, and important distinctions for performance and…

Parallel port: history, design, standards and legacy Parallel port A computer interface once common for printers and peripherals, the parallel port provided parallel data transfer and evolved through IEEE 1284 modes before being superseded by USB…

Parameter (computer science) Named inputs used by routines and programs to receive values that control execution. Covers formal vs actual parameters, passing methods, defaults, typing, scope, and uses in APIs…

Partition editor — software for creating and managing disk partitions Partition editor Overview of partition editors: purpose, common operations, partition table types, command-line and graphical tools, uses, and safety practices for managing storage partitions.

Pascal (programming language) Pascal Pascal is a procedural, strongly typed programming language developed for teaching structured programming and data structuring. It influenced many later languages and saw wide use…

Passbook (Apple mobile application) Passbook (application) Passbook is Apple’s iOS app for storing digital passes—boarding passes, tickets, coupons and cards—introduced in 2012 and later evolved into Apple Wallet; it supports location/time…

Password (authentication credential) Password A password is a secret word or string used to verify identity. This article explains types, storage and verification, common threats and protections, history, and practical guidanc…

PCLinuxOS: a user-friendly rolling-release Linux distribution PCLinuxOS PCLinuxOS is a free, desktop-oriented Linux distribution noted for its ease of use, live media installer, RPM-based package system, and a rolling-release update model maintained by…

PeaZip: open-source file archiver, manager and encryption utility PeaZip PeaZip is a free, open-source, cross-platform archiver and file manager for Windows and Linux that supports many formats, offers encryption, a portable build, and a native PEA arch…

Pebibyte (PiB): the binary data size unit Pebibyte A pebibyte (PiB) is a binary unit of digital information equal to 2^50 bytes (1,125,899,906,842,624 bytes). It is distinct from the decimal petabyte (PB) and used for precise compu…

Pedal (foot-operated control) Pedal A pedal is a lever or control worked by the foot to operate machinery, instruments or vehicles. This entry covers forms, mechanics, history, common uses and distinctions.

Pen: history, types, components, uses, and cultural significance Pen Comprehensive overview of pens: origins, major types (reed, quill, dip, fountain, ballpoint, stylus), key parts, typical uses in writing and art, and how pens shaped communication…

Pendulum clock: mechanism, history, and uses Pendulum clock A pendulum clock uses a swinging weight as its timekeeper. This article explains its operation, main parts, historical development since 1656, common types and why it was long the…

Penetrometer: instrument for measuring material resistance Penetrometer A penetrometer is an instrument that measures the resistance of a material—commonly soil, pavement or fruit—to penetration. It is used in geotechnics, agriculture and planetary exp…

Pentium — Intel x86 microprocessor brand and product family Pentium Pentium is a long-standing Intel brand for x86-compatible microprocessors introduced in 1993. It has evolved through multiple generations and today denotes entry- to mid-level CPUs…

Intel Pentium 4 Pentium 4 Intel Pentium 4: a NetBurst-based x86 microprocessor family introduced in 2000. Known for high clock speeds, a very deep pipeline and thermal challenges; largely replaced by the Co…

Peripheral equipment: input, output and the devices that extend a computer Peripheral equipment Peripheral equipment (I/O devices) are hardware units that connect to a computer to provide input, output, or both. This article explains types, connections, controllers, history,…

Periscope: design, history, and uses Periscope A periscope is an optical device for observing from cover or below a surface. This article covers its principles, components, historical development, military and civilian uses, an…

Personal computer A personal computer (PC) is a small, general-purpose computing device designed for use by one person. This article explains its parts, history, common uses, and how it differs from…

Personal digital assistant (PDA) Personal digital assistant Handheld computing devices intended as electronic organizers. PDAs offered calendars, contacts, notes and simple apps, later converging with phones and networks to form modern smar…

Personal identification number (PIN): purpose, format, history and security Personal identification number A personal identification number (PIN) is a short numeric or alphanumeric code used to verify identity for banking, payments, devices and secure systems; this article covers format…

Pet door (cat flap or doggie door) Pet door A small hinged or electronic panel installed in doors, walls, or windows to let companion animals enter and exit independently; types range from simple flaps to programmable microc…

Petabyte (PB): definition, conversions, and typical uses Petabyte A petabyte (PB) equals 10^15 bytes in the decimal system. This article explains what a petabyte is, conversion rules, the binary distinction (pebibyte), and common uses in science,…

Phablet — hybrid smartphone and tablet device Phablet A phablet is a mobile device that combines elements of smartphones and tablets, typically with a 5.1–7 inch screen. This article explains design, history, uses, and how it differs…

Phone connector (audio jack): overview, types, and uses Phone connector A concise guide to the phone connector (audio jack): what it is, common sizes and wiring (TS/TRS/TRRS), history, typical uses in instruments and headphones, and balanced vs unbalan…

Phonograph: mechanical recording and playback of sound Phonograph A mechanical system first commercialized in the late 19th century for recording and reproducing sound on cylinders and discs; later known as the gramophone or record player.

Photocopier (copy machine) Photocopier A photocopier reproduces text and images from an original paper onto another sheet. Uses xerography or digital scanning, common in offices and public facilities for fast document d…

Photodetector: devices that sense and convert light into electrical signals Photodetector Photodetectors convert incoming light into electrical signals. Common types include photoresistors, photodiodes, phototransistors, CCD/CMOS arrays and photomultipliers; used in ima…

Photodiode: principles, types, performance and practical uses Photodiode Comprehensive overview of photodiodes: operation principles, common types (PIN, APD), materials, key parameters, biasing modes, noise, packaging and typical applications in sensing…

Photoflash capacitor A photoflash capacitor stores electrical energy for camera flashes and strobes, releasing it in a very short pulse to produce bright light. It is optimized for fast discharge, safe…

Photolithography: Light-driven patterning for printing and semiconductor manufacturing Photolithography Photolithography uses light and photosensitive materials to transfer patterns onto surfaces, from mass photographic printing to microfabrication of semiconductor devices.

Photomask: stencil used in photolithography for microfabrication Photomask A photomask is an optical stencil used in photolithography to transfer circuit patterns onto substrates. This article explains construction, types, production, uses, and important…

Photomultiplier tube (PMT) Photomultiplier tubes A photomultiplier tube (PMT) is a vacuum photodetector that converts single photons into amplified electrical pulses by photoemission and a dynode cascade; used for ultra-low-light…

phpBB — Open-source bulletin board (forum) software phpBB phpBB is a free, open-source bulletin board system written in PHP. It supports multiple SQL databases, customizable skins and extensions, and a broad community for hosting online f…

Physical Address Extension (PAE) — overview, workings, history and uses Physical Address Extension Physical Address Extension (PAE) is an x86 CPU feature that lets 32-bit processors address more than 4 GB of physical memory (up to 64 GB) by extending page table formats and physi…

Pianola (player piano): self-playing piano and its mechanism Pianola A pianola, or player piano, is an acoustic piano fitted with a pneumatic or electric mechanism that reads punched paper rolls to play music automatically, popular in homes and venu…