Basic functions of any operating system

Managing Resources – These programs coordinate all the computer’s
resources including keyboard, mouse, printer, monitor, storage devices and
memory.
Providing a user interface – Users interact with application programs and computer hardware
through a user interface. Almost all operating systems today provide a windows-like Graphical
User Interface (GUI) in which graphic objects called icons are used to represent commonly used
features.
Running applications – These programs load and run applications such as word processors and
spreadsheets. Most operating systems support multitasking, or the ability to run more than one
application at a time
Support for built-in utility programs –The operating
system uses utility programs for maintenance and repairs.
Control to the computer hardware – The operating system sits between the programs and the
Basic Input Output System (BIOS).
More informations: http://schoolnet.gov.mt/cs/Resources/Sam%20Cefai/operating%20system%202.pdf