On this day in 1971, the first edition of the Unix Programmer's Manual was dated, written for the version of Unix that ran on the PDP-11 at the time. Dennis Ritchie wrote that he was amazed by what has survived so long: "the semantics of important system calls, and the important early commands." Every man page I've ever pulled up has a great-grandparent in there. (Sources: Dennis Ritchie's manual page, Wikipedia) #Unix #TechHistory #RetroComputing