Main Memory

Stores data and programs. This Memory is typically volatile; that is, when the computer is shut down, the contents of the memory are lost. In contrast, the contents of disk memory are retained even when the computer system is shut down. Main memory is also referred to as real memory or primary memory.

Skipping down two levels, main memory is the principal internal memory system of the computer. Each location in main memory has a unique address, and most machine instructions refer to one or more main memory addresses.

Main memory is usually extended with a higher-speed, smaller cache.