Today we are looking at VisiCalc, the original killer app. Hitting the market in 1979, VisiCalc was the first computer spreadsheet program. Through it's 6 year lifespan it was ported to everything from the Apple II to the IBM PC to the Apple III. It dominated the market and then... it disappeared. Selected Sources:
https://conservancy.umn.edu/handle/11299/113026 - Oral History with Bricklin and Frankston
http://www.bricklin.com/history/intro.htm - Bricklin's personal website
https://sci-hub.se/10.1109/MAHC.2007.4338439 - The creation and demise of VisiCalc