A computer is a device that processes data according to a set of instructions known as a program. The equipment is known as the hardware and the programs and data are the software. A special set of programs, called an operating system, provides an interface for the user and allows applications programs to communicate with the hardware. Common application programs include wordprocessors for creating and editing texts, spreadsheets for calculating mathematical formulae and databases for storing data in a way that allows the data to be sorted and searched. Anti-virus programs are used to detect and remove viruses (harmful programs that can reproduce themselves and attach themselves to other programs). Some operating systems have graphical (user) interfaces that allow the computer user to select items from menus (lists of choices) and to start programs using an input device called a mouse. This is done by pressing a button on the mouse i.e. clicking the mouse. The main device for inputting the data is a typewriter-style keyboard and the output is commonly displayed on a monitor screen that looks like a small television screen.
There is a range of sizes and types of computers. Those designed for use by one person at a time are known as personal computers (PCs) although the term PC is usually only applied to personal computers that are compatible with the standards laid down by the company known as IBM (International Business Machines). Personal computers include desktop computers (for use on an office desk) and handheld computers that can be carried around by the user. Electronics can be added to desktop computers by plugging in expansion cards (electronic circuit boards that can be plugged into special sockets called expansion slots).
It is also possible to build all the main parts of a computer into one electronic integrated circuit packaged as a single electronic chip (the common name for a microchip; an electronic integrated circuit in a small package) i.e. the 'computer on a chip'. This enables computers to be built into other devices including household devices such as washing machines and fridges and to be incorporated into plastic cards i.e. smart cards, which are able to store information such as health records, drivers' licences, bank balances, etc. Devices that include a computer circuit are commonly referred to as smart devices. A multimedia computer can process different forms of data including text, graphics, audio (sound), animation and video. This enables computer systems to be used for a combination of education and entertainment, sometimes referred to as edutainment.
Unlike most machines, computers do not have a fixed purpose. They are multi-purpose tools. They can be used in a very wide variety of situations and are found in a wide range of systems including security systems, cars and phones. Advanced systems, known as expert systems, enable computers to 'think' like experts. Medical expert systems, for example, can help doctors diagnose an illness and decide on the best treatment. A variety of devices known as peripherals can be added externally to a computer. One of the most common peripherals is a printer used for printing the computer output (the processed data or signals that come out of a computer system) on paper. A digital camera allows photographs to be input to a computer for editing.
Not all computer systems are compatible i.e. they cannot use the same programs and data. Connecting computers together to form a network can provide the 'connectivity' required to enable computers and software to communicate and to share resources. Networks connected together form an internet. The connection of networks throughout the world is known as the Internet (note that a capital I is used) or, more simply, the Net. Services such as these allow people to telecommute (use their computers to stay in touch with the office while they are working at home). Computer uses mentioned in this unit include producing greetings cards; learning, using three-dimensional graphics programs called 'Splat the Cat' and 'Pets 3'; using the Microsoft Word wordprocessing program including features such as clipart (ready-drawn graphic images that can be inserted into documents); communicating on the Internet using email and chat programs including the use of email attachments (other types of files e.g. video files attached to simple email text messages); distance learning and videoconferencing (a form of communication over a network that uses video cameras so that the people taking part can see and hear each other); electronic classrooms or boardrooms; browsing the Web (moving from webpage to webpage using a Web browser program); selling, using a website; painting; scanning pictures; downloading music and creating CD-ROMs (compact disk read only memory, commonly referred to as CDs). CD-ROMs are storage devices that use laser light for reading and writing data. The most common storage device is a hard disk (a set of aluminium disks coated in a magnetic material and enclosed in a vacuum-sealed case) used for storing the operating system and applications programs as well as the user's data.