operating system
software, consisting of programs and data, that runs on computers, manages computer hardware resources, and provides common services for execution of various application software
What are the major operating systems for personal computers?
  1. Microsoft Windows
  2. Mac OS
  3. UNIX
  4. Linux
Functions of an operating system
  1. Processor management
  2.  Memory management
  3.   Input/output management
  4.   File management
  5.   Establishment and enforcement of a priority system


Processor management
Assignment of processor to different tasks being performed by the computer system.
Memory management
Allocation of main memory and other storage areas to the system programs as well as user programs and data.
Input/output management
  Co-ordination and assignment of the different output and input device while one or more programs are being executed.

What is File management
Ensures that files in secondary storage are available when needed. Manages reading and writing in the file system and they are protected from access by unauthorized users.
Establishment and enforcement of a priority system
Determines and maintains the order in which jobs are to be executed in the computer system.