KIET-LMS

An operating system is software that manages the computer hardware, as well as providing an environment for application programs to run. Perhaps the  most visible aspect of an operating system is the interface to the computer system it provides to the human user.

To best utilize the CPU, modern operating systems employ multiprogramming, which allows several jobs to be in memory at the same time, thus ensuring that the CPU always has a job to execute. Time-sharing systems are an extension of multiprogramming wherein CPU scheduling algorithms rapidly switch between jobs, thus providing the illusion that each job is running concurrently.

The operating system must ensure correct operation of the computer system. To prevent user programs from interfering with the proper operation of the system, the hardware has two modes: user mode and kernel mode.

Operating systems must also be concerned with protecting and securing the operating system and users.