VisiCalc

VisiCalc was the original computer spreadsheet program. Very popular among early personal computer users, it could also be said to have been the first killer app . Many people bought computers just so they could use VisiCalc. Created by Dan Bricklin and Bob Frankston in Bricklin's attic in 1979, VisiCalc originally ran on Apple computers. An IBM PC version became available in 1981.

Prior to VisiCalc, a spreadsheet required that a user who changed one figure on a spreadsheet had to manually recalculate the effect of that change on other figures. VisiCalc not only exploited the computer to automatically update a spreadsheet but allowed the user to immediately see all the changes.

Never patented, VisiCalc was soon followed by what became an even more popular spreadsheet program, Lotus 1-2-3 . Later, Microsoft developed Excel and included it in its widely-sold Office suite.

VisiCalc was coded in assembler for the microprocessor in the Apple II and tested in a Multics system at MIT. The original VisiCalc for the IBM PC can still be downloaded and run on IBM PC systems using MS-DOS emulation.