Glossary of Computer Terms

Computer Terms Glossary

This page is meant to serve as a guide to the vast quantity of computer terms and acronyms in common use for the casual computer user. It is divided into two main sections, the first is dedicated to the basics and is meant more for beginners, while the second is meant instead to be used as a reference. In reality many of the terms in the second section are still quite common; the first section was deliberately kept as short as possible.

Terms in the second section may be looked up by either using the "find in page" function of your browser, or by appending "#term" (without the quotes and where term is the term of interest) to the "URL" or "go to" section of your browser, keeping in mind that case matters. The best method of searching for a term though is to use the Search Interface that will return not only the specific term sought but also other entries that reference it. Be aware that the terms referenced in the second part of this page will freely assume familiarity with the first part.

If you are instead actually trying to figure out what a particular filename extension means, you might instead try the filename extensions page.

If you want something added or see a problem with something already here (but keep in mind this guide is not meant to be overly technical) please send .


The term personal computer properly refers to any desktop, laptop, or notebook computer system. Its use is inconsistent, though, and some use it to specifically refer to x86 based systems running MS-DOS, MS-Windows, GEOS, or OS/2. This latter use is similar to what is meant by a WinTel system.
A personal digital assistant is a small battery-powered computer intended to be carried around by the user rather than left on a desk. This means that the processor used ought to be power-efficient as well as fast, and the OS ought to be optimized for hand-held use. PDAs typically have an instant-on feature (they would be useless without it) and most are grayscale rather than color because of battery life issues. Most have a pen interface and come with a detachable stylus. None use mouses. All have some ability to exchange data with desktop systems. In terms of raw capabilities, a PDA is more capable than an organizer and less capable than a laptop (although some high-end PDAs beat out some low-end laptops). By far the most popular PDA is the Pilot, but other common types include Newtons, Psions, Zauri, Zoomers, and Windows CE hand-helds. By far the fastest current PDA is the Newton (based around a StrongARM RISC processor). Other PDAs are optimized for other tasks; few computers are as personal as PDAs and care must be taken in their purchase. Feneric's PDA / Handheld Comparison Page is perhaps the most detailed comparison of PDAs and handheld computers to be found anywhere on the web.
Roughly speaking, a platform represents a computer's family. It is defined by both the processor type on the hardware side and the OS type on the software side. Computers belonging to different platforms cannot typically run each other's programs (unless the programs are written in a language like Java).
If something is portable it can be easily moved from one type of computer to another. The verb "to port" indicates the moving itself.
A printer is a piece of hardware that will print computer information onto paper.
The processor (also called central processing unit, or CPU) is the part of the computer that actually works with the data and runs the programs. There are two main processor types in common usage today: CISC and RISC. Some computers have more than one processor and are thus called "multiprocessor". This is distinct from multitasking. Advertisers often use megahertz numbers as a means of showing a processor's speed. This is often extremely misleading; megahertz numbers are more or less meaningless when compared across different types of processors.
A program is a series of instructions for a computer, telling it what to do or how to behave. The terms "application" and "app" mean almost the same thing (albeit applications generally have GUIs). It is however different from an applet. Program is also the verb that means to create a program, and a programmer is one who programs.


The PA-RISC is a RISC processor developed by Hewlett-Packard. It is currently produced only by HP. At the moment only one OS runs on PA-RISC based machines: HP-UX. There is an effort underway to port Linux to them, though.
Palm DOC
Palm DOC files are quite similar to (but slightly less capable than) Newton books. They were designed for Palm Pilots but can now be read on a couple other platforms, too. They are a specific type of e-book.
Palm Pilot
The Palm Pilot (also called both just Palm and just Pilot, officially now just Palm) is the most popular PDA currently in use. It is one of the least capable PDAs, but it is also one of the smallest and least expensive. While not as full featured as many of the other PDAs (such as the Newton) it performs what features it does have quite well and still remains truly pocket-sized.
Loosely speaking, parallel implies a situation where multiple things can be done simultaneously, like having multiple check-out lines each serving people all at once. Parallel connections are by their nature more expensive than serial ones, but usually faster. Also, in a related use of the word, often multitasking computers are said to be capable of running multiple programs in parallel.
Sometimes due to hardware limitations, disks have to be divided into smaller pieces. These pieces are called partitions.
Named after the mathematician Blaise Pascal, Pascal is a language designed by Niklaus Wirth originally in 1968 (and heavily revised in 1972) mostly for purposes of education and training people how to write computer programs. It is a typically compiled language but is still usually slower than C or FORTRAN. Wirth also created a more powerful object-oriented Pascal-like language called Modula-2.
The DOS produced by IBM designed to work like MS-DOS. Early versions of it bear striking similarities to the earlier CP/M, but it utilizes simpler commands. It provides only a CLI, but either Windows 3.1 or GEOS may be run on top of it to provide a GUI. It only runs on x86 based machines.
The Personal Computer Memory Card International Association is a standards body that concern themselves with PC Card technology. Often the PC Cards themselves are referred to as "PCMCIA cards". Frequently flash memory can be found in PC card form.
Perl is an interpreted language extremely popular for web applications.
The Commodore PET (Personal Electronic Transactor) is an early (circa 1977-1980, around the same time as the Apple][) home computer featuring a ROM-based BASIC developed by Microsoft which it uses as a default "OS". It is based on the 65xx family of processors and is the precursor to the VIC-20.
The PETSCII character set gets its name from "PET ASCII; it is a variant of the ASCII character set originally developed for the Commodore PET that swaps the upper and lower case characters and adds over a hundred graphic characters in addition to other small changes. If you encounter some text that seems to have uppercase where lowercase is expected and vice-versa, it is probably a PETSCII file.
Named with a recursive acronym (PHP: Hypertext Preprocessor), PHP provides a means of creating web pages that dynamically modify themselves on the fly.
Ping is a protocol designed to check across a network to see if a particular computer is "alive" or not. Computers that recognize the ping will report back their status. Computers that are down will not report back anything at all.
The smallest distinct point on a computer display is called a pixel.
A plug-in is a piece of software designed not to run on its own but rather work in cooperation with a separate application to increase that application's abilities.
There are two common meanings for this word. The first is in the geometric sense; a position in space without size. Of course as applied to computers it must take up some space in practise (even if not in theory) and it is thus sometimes synonomous with pixel. The other meaning is related most typically to fonts and regards size. The exact meaning of it in this sense will unfortunately vary somewhat from person to person, but will often mean 1/72 of an inch. Even when it does not exactly mean 1/72 of an inch, larger point sizes always indicate larger fonts.
The PowerPC is a RISC processor developed in a collaborative effort between IBM, Apple, and Motorola. It is currently produced by a few different companies, of course including its original developers. A few different OSes run on PowerPC based machines, including Mac OS, AIX, Solaris, Windows NT, Linux, Mac OS X, BeOS, and AmigaOS. At any given time, the fastest processor in the world is usually either a PowerPC or an Alpha, but sometimes SPARCs and PA-RISCs make the list, too.
This simply means to be supplied by only one vendor. It is commonly misused. Currently, most processors are non-proprietary, some systems are non-proprietary, and every OS (except for arguably Linux) is proprietary.
A protocol is a means of communication used between computers. As long as both computers recognize the same protocol, they can communicate without too much difficulty over the same network or even via a simple direct modem connection regardless whether or not they are themselves of the same type. This means that WinTel boxes, Macs, Amigas, UNIX machines, etc., can all talk with one another provided they agree on a common protocol first.
The Psion is a fairly popular brand of PDA. Generally, it is in between a Palm and a Newton in capability. It runs the EPOC OS.
Python is an interpreted, object-oriented language popular for Internet applications. It is extremely portable with free versions existing for virtually every platform.