Asked about the three-key shortcut while at Harvard University, Gate said it could have been a single button, "but the guy who did the IBM keyboard design didn't want to give us our single button," ABC reported Thursday.
"We programmed at a low level," Gates said. "It was a mistake."
The exchange was first reported by Geekwire.
The "guy" at the keyboard was IBM PC engineer David Bradley, who said in an interview several years ago that control-alt-delete was meant to be something used only in development.
"It wouldn't be available elsewhere," he said.
Well, since the command was introduced in 1981, it still lives in Windows, including the current Windows 8 operating system.
A 2010 Indianapolis Star article said the original idea was to create a way to restart the computer. Bradley said he chose those three keys because he didn't want people to erroneously hit the keys -- and their placement on the original IBM keyboard required two hands.