User's groups started in the early days of mainframe computers, as a way to share sometimes hard-won knowledge and useful software, usually written by end users independently of the factory-supplied programming efforts. SHARE, a user group originated by aerospace industry corporate users of IBM mainframe computers, was founded in 1955 and is the oldest computer user group still active. DECUS, the DEC User's Society, was founded in 1961 and its descendant organization still operates. The Computer Measurement Group (CMG) was founded in 1974 by systems professionals with a common interest in (mainframe) capacity management, and continues today with a much broader mission. The first UNIX user's group organized in 1978.
Users' groups began to proliferate with the microcomputer revolution of the late 1970s and early 1980s as hobbyists united to help each other with programming and configuration and use of hardware and software. Especially prior to the emergence of the World Wide Web, obtaining technical assistance with computers was often onerous, while computer clubs would gladly provide free technical support.
A users' group may provide its members (and sometimes the general public as well) with one or more of the following services:
User's groups may be organized around a particular brand of current hardware (IBM, Macintosh), current software and operating systems (Linux, Microsoft Windows, Clipper), or more rarely may be dedicated to obsolescent systems or historical computers, for example Apple II, PDP-11, Osborne.