Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Comparison of the Microsoft Windows and Linux computer operating systems is a common topic of discussion among their users. Windows is the most popular proprietary personal computer operating system, while Linux is the most prominent operating system that is free software (note that some proprietary components, such as compiled, binary only drivers provided by hardware manufacturers, are included in many Linux distributions). Both operating systems not only compete for user base in the personal computer market, but also compete in the server and embedded systems markets and are used in homes, schools, businesses, government offices, and supercomputers. Windows dominates in the desktop and personal computer markets with about 90% of the desktop market share, and accounted for about 66% of all servers sold (not used) in the year 2007.[citation needed] In server revenue market share (2007Q4) Windows achieved 36.3% and Linux achieved 12.7%. As of June 2009, Linux powered 88.6% of the world's most powerful supercomputers, compared to Windows' 1.0%.