The operating makes sure that the user does't realize which hardware he uses - so it abstracts from the machine level to another level wich the user or programer is more familiar with.

A computer cannot work without an operating system. There are different fields of use where are different demands to the system.

• Webserver: has to work reliably under high load.
• Gamecomputer: has to provide fast graphics.
• Supercomputer: has to handle many tasks simultanously.