2. 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.

ROM is a type of memory that retains its data even without power, so even when the computer is switched off, it will not lose the data which is saved onto it.

This kind of memory is needed because the computer must be able to obtain instructions from the moment it is switched on and it must know some basic things about the hardware that makes up the machine i.e. 'its configuration settings'.

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 also called 'non volatile memory'