Overlay (programming)

To enable a process to be larger than the amount of memory allocated to it, we can use overlays.

The idea of overlays is to keep in memory, only those instructions and data, which are needed at a given time.When other instructions are needed, they are loaded into space occupied previously by instructions that are no longer needed.

Special relocation and linking algorithms are needed to construct overlays. As in dynamic loading, overlays do not require any special support from the operating system.