VisiCalc

In 1979, Harvard student Dan Bricklin was watching his professor correct entries in a table of finance data on a chalkboard. After correcting a mistake in one entry, the professor proceeded to correct the corresponding marginal entries. Bricklin realized that such tedious work could be done much more easily and accurately on his new Apple II microcomputer. This resulted in his invention of VisiCalc, the first spreadsheet computer program for microcomputers. Many agree that that innovation transformed the microcomputer from a hobbyist's game platform to a serious business tool.

The consequence of Bricklin's VisiCalc was a paradigm shift in commercial computing. Spreadsheet calculations, an essential form of commercial data processing, had until then required very large and expensive mainframe computing centers. Now they could be done by a single person on a personal computer. When the IBM PC was released two years later, VisiCalc was regarded as essential software for business and accounting.