"The Apple II (often rendered Apple ][ or Apple //) was one of the first highly successful mass produced microcomputer products, designed primarily by Steve Wozniak, manufactured by Apple Computer (now Apple Inc.) and introduced in 1977. In terms of ease of use, features and expandability the Apple II was a major technological advancement over its predecessor, the Apple I, a limited production bare circuit board computer for electronics hobbyists which pioneered many features that made the Apple II a commercial success. Introduced at the West Coast Computer Faire in 1977, the Apple II was among the first successful personal computers and responsible for launching the Apple company into a successful business (and for allowing several related companies to start at all). Throughout the years, a number of different models were introduced and sold, with the most popular model manufactured having relatively minor changes even into the 1990s. By the end of its production in 1993, somewhere between five and six million Apple II series computers (including approximately 1.25 million Apple IIGS models) had been produced"
Source: Wikipedia, "Apple_II", available under the CC-BY-SA License.