The most important system software package for any computer is its operating system. Every computer system runs under the control of an operating system. Operating systems for computers that are shared by many users are considerably more complex than operating systems for personal computers.
Computer hardware is virtually useless without computer software. Software is the programs that are needed to accomplish the input, processing, output, storage, and control activities of information systems.
Computer software is typically classified into two major types of programs: system software and application software.