From a story on newyorker.com by Kyle Chayka headlined “The Birth of the Personal Computer”:

In 1979, two M.I.T. computer-science alumni and a Harvard Business School graduate launched a new piece of computer software for the Apple II machine, an early home computer. Called VisiCalc, short for “visible calculator,” it was a spreadsheet, with an unassuming interface of monochrome numerals and characters. But it was a dramatic upgrade from the paper-based charts traditionally used to project business revenue or manage a budget. VisiCalc could perform calculations and update figures across columns and rows in real time, based on formulas that the user programmed in. No more writing out numbers painstakingly by hand.