3. Embedded system cont.

Just like every other type of modern computer, embedded systems have both hardware and software. But they differ in two key respects:

• The software of an embedded system is custom-written, to work with its specific hardware. Non-embedded systems are more general-purpose.
• Embedded computer software is usually loaded into non-volatile memory, rather than RAM. It runs as soon as the power is switched on.

More complicated embedded systems such as vending machines or ATMs might have operating systems that allow settings to be changed. But they only allow access to those settings by the manufacturer or expert technicians. If user inputs are required at all, they are limited to a pre-built menu system.