9. Memory

The two main types of memory that you need to clearly understand are Random Access Memory (RAM) and Read Only Memory (ROM)

Read Only Memory (ROM)

Data stored on ROM is not erased when the power is switched off - it is permanent. This is called 'non volatile memory'.

The ROM chip is used to hold data that cannot be changed by the user. Instructions related to the operating system are stored on ROM chips when the computer is manufactured.

This data will usually be the software that tells the computer how to load the operating system when it is switched on or re-booted.

Random Access Memory (RAM)

In contrast to ROM, RAM is volatile memory. The data is held on a chip, but only temporarily. The data disappears if the power is switched off.

Have you ever forgotten to save your work before the computer crashed? When you log back on, your work has disappeared. This is because it was stored in RAM and was erased when the PC was switched off.

However, if you had saved your work, it would have been transferred from RAM to the hard disk where it would have been stored safely.

For more details about RAM, visit the 'storage devices' mini website.