computer software, also called software, is a set of instructions and documentation that tells a computer what to do or how to perform a task. software includes all different programs on a computer, such as applications and the operating system. applications are programs that are designed to perform a specific operation, such as a game or a word processor. the operating system (e.g. mac os, microsoft windows, android and various linux distributions) is a type of software that is used as a platform for running the applications, and controls all user interface tools including display and the keyboard.