VisiCalc was the first killer app. It became the reason people bought a personal computer.
You can read a paper presented in 1979 by one of its creators, Bob Frankston, in which he explains what it does and why it’s better than learning BASIC. Yes, VisiCalc’s competitor was a programming language. (Here’s Bob reading part I of his paper.)
Bob of course acknowledges Dan Bricklin as VisiCalc’s original designer. (Here’s Dan re-reading the original announcement.) Bob and Dan founded the company Software Arts, which developed VisiCalc. Since then, both have spent their time in commercial and public-spirited efforts trying to make the Internet a better place for us all.