What is Operating System?

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 What is operating system - 

An operating system is the software that manages the computers hardware and provides a convenient and safe environment for running programs.

It acts as an interface between programs and hardware resources that these programs access (like memory, hard disk and printer).

It is loaded into memory when a computer is booted and remains active as long as the machine is up.

Key Features of an operating system - 

The operating system allocates memory for the program and loads the program in it.

It also loads the CPU registers with control information related to the program. The registers maintain the memory locations where each segment of a program is stored.

The instructions provided in the program are executed by CPU. The operating system keeps track of the instructions that was executed last. This enables it to resume a program if it had to be taken out of the CPU before it completed execution.

If the program needs to access the hardware, it makes a call to the operating system rather than attempt to do the job itself. For instance, if the program need to read a file on disk, the operating system directs the disk controller to open the file and make the data available to the program.

After the program has completed execution, the operating system cleans up the memory and registers and makes them available for the next program.

The operating system creates a process for each program and then control the switching of these processes.

Different types of an operating system - 

Windows, Mac O.S., Linux, Unix

Different flavors of Unix O.S. - 

HP-US, IBM-AIX, Sun-Solaris, IRIX, Mac O.S.

Different flavors of Linux O.S. -

Redhat Enterprise Linux, Fedora, Debian, Ubuntu, Suse Enterprise.

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