Spreadsheet

The spreadsheet emerged from a moment of frustration at Harvard Business School. Dan Bricklin watched a professor construct a financial model on a blackboard—rows and columns forming a table, formulas and data filling cells. When the professor found an error, he had to erase and rewrite a cascade of dependent values. Bricklin realized a computer could do this automatically. Change one cell; recalculate everything.

Bricklin and his MIT classmate Bob Frankston formed Software Arts and built VisiCalc in a two-month sprint during the winter of 1978-79, working from an apartment at 231 Broadway in Arlington, Massachusetts. The concept was simple but transformative: an electronic grid where any cell could contain a number or a formula referencing other cells. Change an input; see the results ripple through the model instantly. What had taken twenty hours of manual recalculation now took fifteen minutes.

VisiCalc launched on October 17, 1979 for the Apple II at under $100. The impact was immediate and startling. When told the $100 software required a $2,000 computer, customers added the Apple II to the order. More than 25% of Apple IIs sold in 1979 were reportedly purchased specifically for VisiCalc. Steve Jobs later said VisiCalc "propelled the Apple II to the success it achieved more than any other single event." Over 700,000 copies sold in six years.

The adjacent possible had been assembling invisibly. The Apple II provided a platform with sufficient memory (at least 32K), a display capable of showing a grid, and a keyboard for input. Accountants and financial analysts had been working with paper spreadsheets for decades—the format was familiar, the limitations painful. The microprocessor had become fast enough to recalculate a reasonable-sized model in acceptable time.

VisiCalc proved software could be a "killer application"—the reason to buy hardware rather than an afterthought. It also demonstrated that personal computers were business machines, not just hobbyist toys. IBM took note; the IBM PC launched in 1981 with its own spreadsheet software available. Lotus 1-2-3 would dominate the PC era; Microsoft Excel would dominate afterward. But the fundamental grid-based interface that Bricklin conceived watching a professor at a blackboard remains the foundation of spreadsheet software today. October 17 is now celebrated as Spreadsheet Day.