Embedded software is computer software, written to control machines or devices that are not typically thought of as computers. It is typically specialized for the particular hardware that it runs on and has time and memory constraints.
A precise and stable characteristic feature is that no or not all functions of embedded software are initiated/controlled via a human interface, but through machine-interfaces instead.
Manufacturers 'build in' embedded software in the electronics of e.g. cars, telephones, modems, robots, appliances, toys, security systems, televisions and set-top boxes, and digital watches etc.