Explain overlay structured program ?
A program having overlays is termed as overlay structured program, here an overlay is a part of program that has similar load origin as some other parts of the program. This type of a program contains
1. A permanently resident portion, termed as the root
2. A set of overlays
The overlay structure of a program is designed through identifying mutually exclusive modules-which is, modules which do not call each other. The fundamental idea is that such modules do not require residing simultaneously in memory. Therefore they are located in various overlays with similar load origin.