The grid of rows and columns that recalculates itself — the tool that turned the paper ledger into a live model of any quantitative situation. From VisiCalc in 1979 through Lotus 1-2-3 and Microsoft Excel, the spreadsheet democratized financial modeling and made 'what-if' analysis universal. It also spread fragile, error-ridden models and, in at least one notorious case, shaped economic policy on a faulty foundation.
In 1978, a Harvard Business School student named Dan Bricklin watched a professor erase and recalculate numbers on a blackboard — redoing the whole grid every time one figure changed. Bricklin thought: what if a grid could recalculate itself? Within months, he and Bob Frankston had built VisiCalc, a program that ran on the Apple II and showed a simple table of rows and columns on screen. Change one number and every cell that depended on it updated instantly. Business people lined up to buy Apple II computers just to run VisiCalc. It was widely described as the first 'killer application' — software so useful it drove hardware sales on its own — though that label, like most superlatives, is one historians use with some caution. What is harder to dispute is the consequence: the spreadsheet turned every desk into a modeling room.