function of operating system

1) to interprate the commands executed by the user.
2) to handle disk input/output settings.
3) loaded in the memory at bootup and remain in the memory at all time.
4) to provid the OS with the machanism in order to see the additional memory.
5) used to access the high memory area. (himem.sys )
6) it allows the rest of the OS and its programs to interact directry with the system hardware and the system BIOS.
7) it sets particular values corresponding to the windows environment.
8) used to run particular programs during startup.