A computer may store a number of different programs in its memory.

Each stored program will receive a time-slice of processing time (typically about 1/50th second) in turn. This happens so fast that it seems that the computer is processing all programs simultaneously.

In practice, most large on-line systems are a mixture of multi-access and multiprogramming systems.

Multi-tasking

Generally applied to PCs...a number of tasks are loaded and processed in turn for short time-slices until completed. It appears that the computer is running several applications at the same time.

Example : On a PC you can have a number of windows open with different applications running in each.