Computer Memory

A computer system needs memory to store the data and the instructions it is going to process. Nothing can be computed until both the program and its data are held somewhere the CPU can reach.

Two ideas anchor this whole topic:

• When we speak of "the memory" of a computer, we usually mean the main or primary memory — the fast, working memory the CPU deals with directly.
• The secondary memory (also called a storage device) is used to store data, instructions and results permanently, for future use.

The two sub-sections that follow develop this in detail:

• 1.3.1 Units of Memory — how memory is measured, from the single bit through nibbles and bytes up to KB, MB, GB and beyond. …