An operating (sometimes abbreviated as "OS") system is a program that acts as an intermediate party between a user of a computer and the computer hardware.
An operating system is the program that, after being initially loaded into the computer by a boot program, manages all the other programs in a computer.
The functions of OS are:
Facilitate creation and modification of program and data files through an editor program
Provide access to compilers to translate programs from high-level languages to machine language
Provide a loader program to move the complied program code to the computer’s memory for execution,
Assure that when there are several active processes in the computer, each will get fair and non-interfering access to the central processing unit for execution (scheduling)
Provide routines that handle the intricate details of I/O programming
Take care of storage and device allocation
Provide for long term storage of user information in the form of files
Permit system resources to be shared among users when appropriate, and be protected from unauthorized or mischievous intervention as necessary.
Handle the booting process.