Answers
Programs and the information they use move from secondary storage into RAM and back again when saved.
The operating system function that keeps track of which areas of RAM are in use by which programs.
Releasing the area of RAM used by a program when it closes, so another program can use it.
The operating system giving each running program its own area of RAM, so they cannot overwrite each other.
Running more than one program at the same time, each held in its own area of RAM.