Write a short note on locality of reference.

Locality of reference means that a program tends to use a small part of its memory addresses again and again over a short time. It has two forms. Temporal locality means that an item used now is likely to be used again soon, as in a loop. Spatial locality means that items near the one just used are likely to be used next, as in an array or in straight-line code. Caches use this idea to keep the active data close to the CPU.