COMPUTERS
Computers do hundreds of different jobs, from word processing to flying aircraft. A computer can perform different tasks because it is a general-purpose electronic machine, controlled by a computer program. Change the program and the computer does a new job. A computer stores data such as numbers, words, sounds and pictures, and processes it under direction of the program.
The first computers to work in the same way as today’s were developed in the 1940s. These huge machines used thousands of thermionic valves. Computers became far smaller with the introduction of integrated circuits in the 1950s, and have continued to become more powerful.
Desktop computers used at home, school and work are called personal computers (PCs). Other types include mainframes, used by large companies for data processing, and supercomputers, for doing complex scientific calculations extremely quickly.
The central processing unit of a PC is contained on a single large integrated circuit called a microprocessor. It has two units – one that carries out calculations and other operations, and another that receives instructions and data from memory.
Parts of a PC
A computer is made up of hardware, its physical parts, and software, made up of the data and programs it stores and uses. The hardware is made up of the computer itself and peripherals, such as monitors and printers that attach to it.
The main part of a personal computer is the central processing unit (CPU), normally simply called the processor, which can be thought of as the computer’s “brain”. It receives instructions from the program and carries them out. Programs and data are stored in the computer’s memory. Rows of metal tracks called buses connect the processor and memory. The data bus carries the data; the address bus tells the memory where the data should come from or go to.
COMPUTER APPLICATIONS
There are two main types of computer software – system software and application software. System software does the computer’s “housekeeping” jobs, such as controlling a printer, or writing data to disc drives. Application software makes the computer do specific jobs.
Most personal computers have application software such as a word processor (for preparing letters and reports), a database (for storing and retrieving information), a web browser (for surfing the World Wide Web) and e-mail software. Games and educational programs are also applications. Office computers may also have software for doing calculations (called spreadsheets), for processing orders, for accounts, for planning projects and for making presentations. Book and magazine designers use publishing software to design and edit pages before they are printed. Engineers and designers use computer-aided design (CAD) software to help them design new products, which they can view on-screen before making the real thing. Details of the parts can be sent to computers that control the manufacturing machines that make the parts.
In most offices, computers are linked together into networks so that they can share programs and data, which are stored on a computer called a server.
Many computers do just one specific job. Examples of these dedicated computers are games machines, in-car navigation computers, and the computers that help to fly airliners and fighter aircraft.
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