How many operating systems are there?

Answer 1

There have been 6 major versions. As of the time of this writing, the current stable release is Windows 7 (however, note that the internal version number is actually NT 6.1). Windows 8 (version NT 6.2) is currently in development.

For most major versions, there have been a few "minor" versions. This was evident in the name up to Windows 3.x. However, commercial branding has made the less evident since the introduction of Windows 95, which shared the same major version number (which was 4.x) with Windows 98 and Windows Me, for example. Windows 2000, Windows XP, and Windows Server 2003 all were version NT 5.x. And finally, Windows Vista, Windows 7, Windows 8, and Windows Server 2008 are all version NT 6.x.

To complicate things a little further, Microsoft started developing Windows NT, geared more toward business users, alongside the main line of Windows versions. This began with the initial release of Windows NT 3.1 in 1993. The Windows NT line was merged into (or, perhaps more properly, transformed into) the main line of Windows releases beginning with NT 5.1, also known as Windows XP. This was the first version of Windows NT to feature both Home and Professional editions, making it successor to both Windows 2000 (business oriented) and Windows Me (consumer oriented).

Answer 2

Due to the relative ease of adapting the Linux kernel and the simple definition of an operating system, there is no finite number. A new Linux-based operating system (a distro) can be created in less than an hour.

Answer 3

Dozens.

The most common are:

Various flavors of Microsoft Windows

Various flavors of Apple Mac OS

Various flavors of Unix (including the swarm of Linux distributions)

Answer 4

1191

Answer 5

100 types