Central Processing Unit (C.P.U.)

The CPU is the "brain" of the computer it is made up of the Control Unit which carries out all the instructions, the Memory which can be sub-divided into ROM (permanent memory) and RAM

(temporary memory) the memory is a very fast access store, information can be read in nanoseconds one thousand millionth of a second and the Arithmetic Unit which performs all calculations, selections and sorting of data.

Input Units

Input units are devices to feed data into the central processing unit all input devices translate information from a form which people can understand into a form the computer can understand

(electrical pulses) not all input devices are work the same way, keyboards for example send the electrical code for the character which has been pressed to the computer. Examples of input devices are the keyboard, mouse, scanner, light pen and joystick.

Output Units

Output units are devices to pass information out of a computer, often in a printed form. Probably the most common output device is the VDU (Visual Display Unit) which shows what the computer is doing. Printers are also widely used, they produce paper copies of information, there are many types of printers from the cheap dot- matrix printers which uses tiny hammers to hit the ink onto the paper to expensive laser printers which work like photocopiers. Some devices can be classed as both input and output devices for example disk drives, magnetic tape recorders and modems can input and output data.

Examples of output devices are the VDU's, printers, plotters, and disks.