Operating system is an interface between computer and hardware and application software. Without OS no computer can be operated. Operating system is regarded as the heart of living being for a computer system.
In other words, OS is defined as a program or suit (support for) of programs that controls the entire operation of the computer, such as recognizing input from keyboard, sending output to the display screen keeping track of files and directories on the disk and controlling peripheral devices such as disk drives and printers.
Basic organization of operating system: