well from the launch, the initial market was to hobbyists and computer enthusiasts. Sales expanded exponentially into the business and professional market, when the spreadsheet program VisiCalc was launched in mid-1979. VisiCalc is credited as the defining killer app in the microcomputer industry. During the first five years of operations, revenues doubled about every four months. Between September 1977 and September 1980, annual sales grew from to . During this period the sole products of the company were the Apple II and its peripherals, accessories, and software. References External links Additional documentation in Bitsavers PDF Document archive Apple II on Old-computers.com Online Apple II Resource Apple2History.org Apple II computers Computer-related introductions in 1977 6502-based home computers 8-bit computers Products and services discontinued in 1979 ca:Apple II