VisiCalc (for "visible calculator") was the first
spreadsheet computer program for
personal computers, originally released for the
Apple II. It is often considered the application that turned the
microcomputer from a hobby for computer enthusiasts into a serious business tool, prompting
IBM to introduce the
IBM PC two years later. Visicalc is considered the Apple II's
killer app. It sold over 700,000 copies in six years, and as many as 1 million copies over its history.