3. Read Only Memory (ROM)

ROM is a special kind of memory which stores the instructions which the computer uses when it 'boots up' - the BIOS (Basic Input Output System).

It allows it to check the type of hard disk installed, the amount of RAM installed (see next page), the type of CPU being used etc.

Because the data is 'read only', it can be read but not changed by the user.

The ROM chip (although there may be more than one) is attached to the motherboard.

The key thing to remember about ROM is that the data is not erased when the computer is switched off - the data is stored permanently. This type of memory is called 'non volatile memory'