Main memory

The main memory is a group of chips inside the processing unit where data is held temporarily during its processing. This memory is instantly accessible on the contrary to the backing storage which is held outside the central processing unit.

The functions of the main memory:

• It holds programs (operating system, application programs). It holds data which has been input
• It stores data which are currently being processed
• It holds intermediate results and output data before sending to an output device

The main memory contains two different types of memory:

• Read only memory(ROM)

  Read Only Memory (ROM) – a non-volatile memory – data is held even when the power is switched off. It is used to hold data that cannot be changed by the user. Programs related to the operating system are stored on ROM chips when a computer is manufactured.

• Random access memory(RAM)

  Random Access Memory (RAM) – is volatile. Data is held on a chip only temporarily. When the power is switched off, the data disappears. RAM is used to hold both data and programs during processing. Most of the memory in a computer system is usually RAM. The capacity of RAM determines the number of programs you can run simultaneously and how fast they operate. It can be expanded by adding extra RAM chips.

Cache memory is a random access memory (RAM) that a computer microprocessor can access more quickly than it can access regular RAM. As the microprocessor processes data, it looks first in the cache memory and if it finds the data there (from a previous reading of data), it does not have to do the more time-consuming reading of data from a larger memory.