NB : This is a very simplified version of the workings of a computer! Reality is much more complex!!

At the heart of every computer is the CPU (Central Processing Unit) - the 'brain' of the computer. It refers to that part of the processor which 'processes' the data and instructions.

The main parts of the CPU are

1. The ALU (Arithmetic and Logic Unit) - which performs the calculations on the data.
2. The Control Unit - which controls all operations inside the computer.
3. Some Memory storage. A register is a place where a single item of data can be stored.

All computers will have at least one input device (eg keyboard, mouse), and at least one output device (eg monitor).

All computers have some memory. The program a computer is running as well as the data are all stored in memory.
(Eg When you write a letter using a word processor then both the word processing program and the letter are stored in memory).

RAM (Random Access Memory) is the type of memory used for temporarily storing programs and data.

Data will need to be moved between several of these elements. The path along which data moves is called a data bus.

When data is saved to (or loaded from) memory, the address of the store location at which it is to be stored (or loaded) must also be sent. The address of data always travels along an address bus.

The Control Unit sends and receives signals from all parts of the computer which makes sure that all processes take place at the right time and in the correct order. These signals travel along a control bus.