What is an Operating System?
An operating system is a program (or set of programs) running on a
computer system that aspires toward two main goals:
- Managing the computer system's resources.
- Computer systems have many resources: memory, disk space,
processor time, printers, terminals, network lines, ...
- Managing a resource can mean (a) making it available to everyone,
(b) making sure no one takes "too much" or something that "isn't their's",
(c) recording who you give it to, and/or (d) all of the above.
- Pretending that the computer system is simpler than it really
is.
- Operating systems have to pretend to at least two classes of
people: users and programmers. They may also have to pretend to system
administrators, other computers, upper management, ...
- At the very least, an operating system has to pretend that all
the resource management that it does isn't going on. On the other
extreme, it may have to present the illusion of a CRAY YMP being "just
like" an IBM PC.
- The thing that an operating system pretends the computer system
to be is sometimes called the virtual machine.
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