[ether_at_cpan]

For those that can remember back that far, MacOS also jumped from 5 to 7. (7 was the first version that supported running multiple applications at once.. not counting the MultiFinder hack that came before it by a few years.)

[blahedo]

It certainly did not. System 6 (including MultiFinder if you had enough RAM to support it ;) was active for several years in the early 90s before System 7 came out. The label "MacOS", meanwhile, didn't show up until a few years after that.

[ether_at_cpan]

Doh, yes, system 6 was current for quite a while. I wonder what other thing from that era I confused it with. I swear something around that time skipped a 6.

[ken]

Solaris skipped from 2.6 to 7. UnixWare also jumped from 2.x to 7. HP/UX skippped from 3.x to 6.x. In perhaps the strangest version jump of all time, Darwin jumped from 1.4.1 to 5.1, as part of Mac OS X 10.1.1.

It seems Unix vendors really don't like low version numbers. Of course, Windows famously jumped from 3.x to 95, so it's not like they're any better.

[Conan_Kudo]

Windows 95 was Windows 4.0. There are several parts of Windows 95 that even indicated this in a user-visible way.

Microsoft was surprisingly good at not skipping numbers, until the jump from Windows 8.1 to Windows 10, which also lead to the NT kernel jumping from 6.x to 10.

[b2gills]

Microsoft had to skip 9 because programmers are lazy.

A lot of programs refused to work if there was a `9` in the version name.

That was of course because those programs needed something newer than Windows 95 or Windows 98. So they just did a string search for `9` in the version name.

There may be a few programs that wouldn't work on `8.9` or `10.9` if they were released for the same reason.

[duskwuff]

System 7 skipped from 7.1 straight to 7.5. (And the pattern was repeated with 8.1 and 8.5.)

[yjftsjthsd-h]

What? https://en.wikipedia.org/wiki/System_6