Earliest OS? (Score 1)

Well, I guess the first question is "what is an OS?" Answers? From there we can kind of look at the following little bits of information I have managed to glean: 1969 Thompson and Ritchie developed the UNIX OS based on the Multiacs OS (developed in the mid '60s). I think that UNIX falls into the category of the first "popular" OS. These are the two earliest multitasking OSs that I know of (any corrections?). The first OS of any type I know of is GM-NAA I/O from 1956, although it wouldn't surprise me if there was something a little earlier. This OS introduced the concept of batch processing, which is with us to today. As a side issue, 1956 seems to be the year that direct keyboard input was added to computers.