[jaydubya2]

1990: Windows 3.0

I would not consider an operating system an "app". I may even have a difficult time considering Windows 3.0 an "operating system".

[ShadowAce]

I would not consider an operating system an "app". I may even have a difficult time considering Windows 3.0 an "operating system".

Windows 3.0 was not an OS. It was a GUI app running on top of DOS, which was the OS.

[carolinalivin]

I think the original MAC OS should be number 1 as an OS, with kudos to the PARC syatem at Palo Alto Xerox for spawning it. Everything done since by MicroSoft and Apple came from that system; apple trying to get better and MS trying to keep up.

[Bloody Sam Roberts]

I may even have a difficult time considering Windows 3.0 an "operating system".

Technically speaking Windows 3.0 was not an OS.

DOS 4.0, DOS 5.0 were the Operating systems. Windows 3.0 and 3.1 were applications that overlayed the OS....i.e, you could delete the Windows directory from the command line using DOS.

With the advent of Windows 95....Windows WAS the OS.