I would say Windows, Mac, and Linix. But, this source says that its ITRON a Japanese operating system. Go to this link for more.
http://www.linuxinsider.com/story/31855.html
1. Windows Seven
2. Windows Xp
3. Mac OS
4. Linux
5. Windows Vista
6. Windows 2003
Windows is the most widely-used desktop operating system made by Microsoft.
One of the most popular and widely used operating system is Microsoft Windows. It is compatible with most devices and has proved to be user-friendly.
windows
MS-DOS was the first widely used operating system
disk operating system
DOS meaning Disc Operating System
Windows XP and Windows 7
Android
The most popular marketing information system is the marketing information system that is the most widely used. This system is used widely due to its popularity.
MS-DOS
Widely used text-based operating system? Well, almost any Unix or Unix-like can be used in this way. X11 GUIs are an entirely optional application. Many Linux users only use the command line.
The MVS operating system was the most commonly used operating system used on mainframe computers. The MVS operating system was developed by IBM and was first released in 1974.