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Every desktop computer uses an operating system .
The Mac OS UNIX Linux is a version of the UNIX operating system that has become very popular over the last 3 years or so. Operating systems are computer programs. An operating system is the first piece of software that the computer executes when you turn the machine on. The operating system loads itself into memory and begins managing the resources available on the computer. It then provides those resources to other applications that the user wants to execute.