Operating system

A computer will always need at least one program running at all times to operate. Under normal operation (in the typical general-purpose computer), this program is the operating system (OS). The operating system decides which programs are run, when, and what resources (such as memory or I/O) they get to use. The operating system also provides a layer of abstraction over the hardware, and gives access by providing services to other programs, such as code ("drivers") which allow programmers to write programs for a machine without needing to know the intimate details of all attached electronic devices.