Explain the term Overlays.
An overlay is an element of program that has the same load origin as several other part of the program. These are used for reduce the main memory requirement of a program. If the problem arises when the size of program exceeds the memory size, so overlays are used. Structure of these programs contains a permanently resident portion, termed as the root.
A set of overlays
To begin with, the root is loaded in memory and specified control for the reasons of execution. Another overlays are overwrites a previously loaded overlay along with similar load origin, this reduces memory requirement of a program. This is also possible to execute programs that size exceeds the memory size.