Q. What is Cache Memory?

Cache memory is a very fast and small memory between CPU and main memory whose access time is closer to processing speed of CPU. It behaves as a high-speed buffer between main memory and CPU and is used to temporarily store presently active data and instructions at the time of processing. Because cache memory is faster than main memory so processing speed is increased by making data and instructions required in present processing available in the cache.

Here obvious question which arises is how system can know in advance that which data and instruction are required in present processing so as to make it available before hand in cache. Answer to this question comes from a principle termed as locality of reference. According to this principle at the time of the course of execution of most programs memory references by processor for both data and instructions tend to cluster. Which is if an instruction is executed there is a probability of nearby instruction being executed soon. Locality of reference is true not only for reference to program instruction but also for references to data. As displayed in Figure below cache memory acts as a small, fast-speed buffer between main memory and processor.