Microsoft Corporation developed 7 Version of windows for Personnel computers except Network Operating system. I think 7 means 7th windows version for Personal computers except Network Operating System. (Windows for work groups Windows 2000 Professional , Windows Sever versions, Windows 2003, Windows 2008)

This is the version of windows developed by Microsoft for Personnel Computes1. Microsoft windows 3.x

2. Microsoft windows 95

3. Microsoft windows 98

4. Microsoft windows Me

5. Microsoft windows XP

6. Microsoft windows Vita

7. Microsoft Windows 7Windows 7 is True Operating System running on personal computer with advance features than previous version for more info Visit Windows 7 home Page.

www.microsoft.com/windows/windows-7/ -

An operating system (OS) is an interface between hardware and user which is responsible for the management and coordination of activities and the sharing of the resources of the computer that acts as a host for computing applications run on the machine.