If you own a personal computer, it probably uses some version of Windows, the operating system sold by the Microsoft Corporation. When Microsoft first designed Windows many years ago, it applied for and received a copyright from the government. The copyright gives Microsoft the exclusive right to make and sell copies of the Windows operating system. So if a person wants to buy a copy of Windows, he or she has little choice but to give Microsoft the approximately $50 that the firm has decided to charge for its product. Microsoft is said to have a monopoly in the market for Windows.