Operating System

Also known as an "OS", this is the software that actually communicates with computer's hardware. Without an operating system, all software programs would be useless. The OS is what allocates memory, processes tasks, accesses disks and peripherials, and acts as the user interface. With an operating system, like the Mac OS or Windows 98, developers can write to a common set of programming interfaces (known as APIs) using the operating system to talk the hardware. Without an operating system, programmers would have to write about ten times as much code to get the same results. Of course, there are people who have to program the operating system itself...