1975: VM/370 CMS demo [video]

The IBM 360 was supposed to be a “universal” computer but IBM struggled to make a “universal” operating system, particularly competing mainframes and minicomputer supported timesharing by the late 1960s but IBM got into the early 1970s without a real product.

Turned out they never developed a universal OS but they did develop virtual machines and could run just as many OS on a computer as they liked. The CMS that they demo here is a single-user OS a lot like MS-DOS or CP/M and if you wanted to develop software you would call up an editor (I think XEDIT) and run a compiler on the command line. It was IBM’s answer to systems like RSTS/E which ran on the overall less capable PDP-11.

The 370 had slow interrupt handling compared to the PDP-11; most minicomputers could respond to and echo individual characters that you typed, the 3270 terminal worked more like web application where you would fill out a form and submit the whole thing, for instance if you typed in a command the terminal would send the whole command when you were done typing.