10. Cache Memory

Most data is stored on the hard disk. When we use that data, it is loaded into RAM because it is much faster to access the data from RAM than from the hard disk. When we looked at the 'immediate access store' earlier, we found out that the CPU needs to access data very quickly. Although RAM is faster than the hard disk, it still isn't fast enough to cope with the speed that the CPU needs to deal with data.

The cache is a special type of computer memory which can be accessed much faster than RAM. The CPU looks in the cache for the data it needs. If the data is there, it will retrieve it and process it. If the data is not there, then the CPU accesses the system memory and then puts a copy of the new data in the cache before processing it.

Cache memory is volatile i.e. when the computer is shut down, the data stored there is lost.