Computer

A computer is a programmable machine that takes in data, follows a stored set of instructions to manipulate it, and produces a result. Unlike a simple calculator that performs one fixed operation, a computer can be given new instructions and thereby take on entirely new tasks without being rebuilt — the property that makes it so broadly useful.

Modern computers span an enormous range, from tiny chips embedded in appliances to data-centre machines and phones in billions of pockets. Despite that diversity, they share a common set of ideas about how information is represented and processed.

Origins and development

Mechanical aids to calculation are ancient — the abacus is thousands of years old — and by the early nineteenth century inventors such as Charles Babbage designed machines with some of the features of a computer, though they were never completed in working form. The key conceptual leap came in the 1930s and 1940s, when mathematicians formalised the idea of a universal machine that could follow encoded instructions, and electronic valves made fast execution possible.

The first electronic general-purpose computers, built during and just after the Second World War, filled whole rooms and consumed large amounts of power. The invention of the transistor in 1947 and the integrated circuit a decade later shrank these machines dramatically, starting the pattern of relentless miniaturisation that continues today.

How a computer works

At its core, a computer manipulates binary digits — bits — each representing a 0 or a 1. Groups of bits stand for numbers, characters, images or sounds according to agreed conventions. The central processing unit (CPU) performs arithmetic and logical operations on these values; memory holds data and instructions close at hand; and storage keeps information persistently when the power is off.

The processor repeatedly fetches an instruction, decodes it and executes it, cycling through a program at enormous speed. Input and output devices connect the machine to the outside world, while buses and networks move data between components. An operating system manages all of this, sharing the machine's resources among the programs that run on it.

Hardware and software

Hardware is the physical equipment; software is the set of instructions. Because software can be changed, the same hardware serves as a video editor, an accounting tool or a game. Programming languages and compilers let people write instructions in human-readable form that are translated into the machine's own codes.

Types of computer

Personal computers, including desktops and laptops, serve individuals. Smartphones are a compact category with similar computing power. Servers handle requests for many users and store shared data, often in data centres. Supercomputers, built from many processors working in parallel, tackle scientific problems such as weather forecasting and molecular simulation. Embedded and single-board computers run dedicated functions inside cars, routers and household devices.

Impact on society

Computers transformed how people work, learn, communicate and entertain themselves. They underlie scientific research, finance, logistics, medicine and government. The internet connected them into a global system, and the falling cost of computing put powerful tools within reach of almost everyone in wealthier regions.

The effects are not uniformly positive. Automation displaces some jobs while creating others; digital systems introduce new security and privacy hazards; and unequal access — the "digital divide" — leaves many people behind. Reliability and the environmental cost of manufacturing and running large computing systems are also growing concerns.

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