System software works in the background to enable the application software to interact with the hardware.  It includes programs that help the computer manage its own internal resources.

The most important system software program is the operating system, which interacts between the application software and the computer.

Some of the more popular operating systems in use today are:  DOS, Windows 95, 98 and 2000, Windows NT, OS/2 Warp, Macintosh operating system, and Unix.