How to use this glossary
Computing vocabulary built up over roughly eight decades, and many terms changed meaning along the way. This list gives short definitions of words that come up often when reading about the history of computers, grouped by theme. It is a starting point rather than a complete dictionary. Where a word has an uncertain or disputed origin, the entry says so instead of guessing.
Core ideas
Algorithm. A step-by-step procedure for solving a problem or completing a task. The idea is much older than electronic machines, and the word is usually traced to the name of a medieval Persian scholar, al-Khwarizmi. Computer algorithms are simply procedures written precisely enough for a machine to carry out.
Analog. Describes information represented by a continuously varying quantity, such as a voltage or the position of a dial. Analog devices were common in early calculation and measurement.
Digital. Describes information represented as separate values, usually numbers. The word comes from the Latin for finger, a reminder that people first counted on their hands.
Binary. A system with two symbols, usually written 0 and 1. Binary numbers are widely used inside computers because parts with two clear states are typically easier to build and keep reliable than parts with many states.
Bit. A single binary digit, either 0 or 1. The term is a shortened form of “binary digit.”
Byte. A group of bits treated as one unit, most often eight today. In earlier decades some machines used other group sizes.
Data. Raw facts or values that a computer stores and processes. Data becomes information when someone interprets it.
Computer. Today, a programmable electronic machine. For a long time before that, the word meant a person who carried out calculations by hand.
Hardware
Processor. The part that carries out instructions. It is also called the central processing unit, or CPU, and in most modern machines it sits on a single chip.
Microprocessor. A complete processor built on one integrated chip. Microprocessors appeared in the early 1970s and made small, affordable computers practical.
Memory. Fast storage that holds the programs and data currently in use. In many machines, main memory is cleared when the power is switched off.
Storage. Longer-term places to keep programs and data, such as tape, magnetic disks and flash chips. Storage generally keeps its contents without power.
Chip. Informal name for an integrated circuit, a set of electronic components made together on a small piece of semiconductor material.
Bus. A set of wires or connections that carries data between components.
Peripheral. Any device attached to the main computer, such as a keyboard, printer or external drive.
Software
Program. A list of instructions for a computer to follow.
Software. The programs and related data that run on hardware, as opposed to the physical machine itself.
Application. A program meant for a user-facing task such as writing, calculating or playing a game.
Operating system. The software that manages the hardware and lets other programs run. Early operating systems were basic job schedulers; later ones added file handling, multitasking and graphical screens.
Firmware. Software stored in a chip so that it stays in place when power is off, often used to start a device or control simple hardware.
Driver. A small program that lets the operating system communicate with a particular piece of hardware.
Source code. The human-readable text of a program, written in one of the many programming languages that developed from the 1950s onward.
Compiler and interpreter. Tools that turn source code into something a machine can run, either all at once or step by step.
Bug. A flaw in a program or machine that causes unexpected behavior. The word predates computers.
Networking
Network. Two or more computers connected so they can exchange data.
LAN. A local area network, linking machines in one building or small site. Local area networks became common in offices and schools during the 1980s.
Internet. A worldwide system of connected networks that agree to exchange data using shared rules.
World Wide Web. A system of linked pages and resources that is reached over the internet. It is one service that runs on the internet, not the internet itself.
Protocol. An agreed set of rules for how two systems communicate.
Packet. A small chunk of data sent across a network. Many early research networks used packet switching, in which messages are split into packets that travel separately and are reassembled at the destination.
Router. A device that forwards packets between networks toward their destination.
Domain name. A readable address, such as one ending in .org, that stands in for a numeric one.
Server and client. A server provides a service or data; a client is the program or device that requests it.
Types of computers
Mainframe. A large, centrally managed computer used by many people or organizations, common from the 1950s through the 1970s and still in use for some tasks.
Minicomputer. A smaller, less costly class of machine that became common from the 1960s.
Workstation. A powerful machine intended for one person, often for engineering or design, especially in the 1980s.
Microcomputer. A computer built around a microprocessor. The term was used heavily in the 1970s and early 1980s, before most people simply said personal computers.
Supercomputer. A machine designed for the most demanding calculations of its time. The label is relative, because what counted as super in one decade became ordinary later.
Embedded system. A small computer built into another device, such as an appliance or a vehicle, usually doing one job.
Common abbreviations
RAM stands for random-access memory, the main working memory in most computers. ROM stands for read-only memory, which holds fixed contents. GUI stands for graphical user interface, meaning screens with windows and icons instead of typed commands. USB stands for Universal Serial Bus, a common standard for connecting peripherals.
A note on changing meanings
Few of these words have stayed still. A computer was once a job title, a supercomputer is a moving target, and the line between a workstation and a desktop machine faded long ago. When reading older sources, it helps to ask what a word meant at the time it was written, not only what it means today.