RAM stands for Random Access Memory.

It is 'Random' because any part of the memory can accessed directly by the computer.

For example, the computer may be wanting data from location 27 in memory and then data from location 3001. RAM allows these locations to be accessed directly.

RAM is very fast compared to a hard disk. A typical hard disk can take 10 milli-seconds to get a piece of data, whilst RAM will take about 10 nano-seconds. That is one thousand million times faster!

RAM is used to store programs and data whilst the computer is switched on. As soon as the power is switched off all the data dissappears.

This is why a computer need both a hard disk and RAM. It uses RAM for speed and the hard disk to store data whilst switched off.

RAM comes in different sizes. A typical RAM device will hold 512 Megabytes. A computer can be installed with a number of RAM devices to increase the amount available. These days it is not unusual to have a Gigabyte of RAM installed.