• 'The process of moving a block of programme code or other data into internal memory, replacing what is previously stored,' according to the definition.
• Overlaying is a method of allowing applications to be larger than the primary memory of a computer. Because of the limitations of physical memory (which is internal memory for a system-on-chip) and the lack of virtual memory features, an embedded would generally use overlays.
• Overlaying needs programmers to break their object code into many entirely independent portions, with the overlay manager attached to the code automatically loading and swapping the required overlays as needed.

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