OPERATING SYSTEM SERVICE

>program execution – system capability to load a program into memory and to run it.
>I/O operations – since user programs cannot execute I/O operations directly, the operating system must provide some means to perform I/O.
>File-system manipulation – program capability to read, write, create, and delete files.
>Communications – exchange of information between processes executing either on the same computer or on different systems tied together by a network. Implemented via shared memory or message passing.
>Error detection – ensure correct computing by detecting errors in the CPU and memory hardware, in I/O devices, or in user programs.