The amount of complexity by which a system is viewed or programmed. The higher the level, the less detail. The lower the level, the more detail. The highest level of abstraction is the entire system.

Abstraction is one of the four cornerstones of Computer Science. It involves filtering out – essentially, ignoring - the characteristics that we don't need in order to concentrate on those that we do.

An interface between hardware and software. A hardware abstraction layer (HAL) is generally used as a common driver for peripheral devices. The application calls the operating system; the OS calls the ...