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Main Memory

ICT > Backing Storage

Main Memory


Memory is a device used to store programs temporarily or permanently.

Main Memory 

Any data or instructions that are to be processed by the CPU must be placed into main memory (sometimes known as primary storage).


Random access memory can be written to, read from and edited. The data in it can be accessed in any order. Ram is volatile memory, which means that it is cleared when the computer is switched off.


Read only memory can also be accessed in random order, but the data in it cannot be changed. ROM is intended for permanent data, necessary for the operation of the computer system. ROM is non-volatile, which means that it retains what is stored in it when the computer is turned off.

Types of ROM:

  • Programmable read-only memory (PROM) has no data locked onto it when first manufactured. But later, a company using PROM chips to make a computer can put in its own information. The data would then be locked in place, so the memory can no longer be changed.
  • Erasable programmable read-only memory gets its original data in the same way PROM does. But, if necessary, the data can be erased using a special light shining on a window on the chip or by electric charge.