“After a stint at Stanford culminating in AI research in 1973, Tesler became a member of the research staff at Xerox’s famed Palo Alto Research Center (PARC).
There, thanks to his intense dislike of operation modes of the era, he conceived and implemented many graphical user interface (GUI) features taken for granted today.
Tesler was very keen on “modeless” software, where a user would not have to, for example, use a keyboard to switch to a command mode before switching back to edit text. Tesler’s vision was that a user’s action should have a consistent effect – there should be no “modes”.
Tell that to most websites today that use popups – which violate every principle of user-driven design Tesler pioneered.
RIP old friend, and thank you.