Cache

Pronounced cash, a special highspeed storage mechanism. It can be either a reserved section of main memory or an independent highspeed storage device. Two types of caching are commonly used in personal computers: memory caching and disk caching. A memory cache, sometimes called a cache store or RAM cache, is a portion of memory made of highspeed static RAM (SRAM) instead of the slower and cheaper dynamic RAM (DRAM) used for main memory. Memory caching is effective because most programs access the same data or instructions over and over. Disk caching works under the same principle as memory caching, but instead of using highspeed SRAM, a disk cache uses conventional main memory. When data is found in the cache, it is called a cache hit, and the effectiveness of a cache is judged by its hit rate.