It's not Corbato's only pioneering effort, either. CTSS' simultaneous usage model reduced the wait time for computer responses from hours to second, making the technology far more practical. His Multics time-sharing system, meanwhile, paved the way for future operating systems like Linux with finer-grained privacy controls, a hierarchical file system and other features that people take for granted today.

He was also the impetus behind "Corbato's Law," which claims that programmers will write the same amount of code regardless of the language they're using. It made a case for using higher-level languages instead of close-to-the-metal code that's typically more time-consuming to write.

Corbato in his later years was aware that passwords had their problems -- the internet made those logins "kind of a nightmare," he told the WSJ. It's no secret that the industry is moving away from passwords to both thwart account hijackers and improve convenience. Still, there's little doubt that Corbato's work helped establish the fundamentals of modern computing.