Every computer requires an operating system. The operating system performs many critical functions which, in turn, allows the computer to perform useful work.
To understand the need for an operating system, it is necessary to understand a little about the structure of the hardware which comprises a computer system. The microprocessor, also known as the CPU, which is located on the motherboard, is the brains of the system. It is the part of the computer which is responsible for executing each of the instructions specified by the software application program. The keyboard and mouse are used for input to the computer, and printers and displays can be used for output.
Random Access Memory (RAM) is used to store data and programs while they are being actively used by the computer. Programs and data cannot be used by the computer unless they are stored in RAM. RAM is volatile memory; that is, the data stored in RAM is lost if the computer is turned off. Hard drives are magnetic media used for long term storage of data and programs. Magnetic media is nonvolatile; the data stored on a disk remains even when power is removed from the computer. DVDs and CD-ROM store data permanently and can be read by the computer but not overwritten.
Printers are used to transfer data from the computer to paper. Sound cards convert data to sound. USB storage devices can be used to store data for backup or transfer to other computers.
The Network Interface Cards (NICs) are used to connect the computer to a network, hard-wired or wireless, so that it can communicate easily with other computers attached to the network.
All of these pieces of the computer must work together. Data must be gotten into the computer and moved about between the various components. Programs must be loaded from long term storage on the hard drive into RAM where they can be executed. Processor time needs to be allocated between running applications. Access to the hardware components of the computer such as RAM, disk drives, and printers by application programs must be managed. It is the task of the operating system to provide these functions. The operating system manages the operation of the computer and of the application software which runs on the computer.
A simple definition of an operating system is that it is a program, much like any other program; it is different only in that its function is to manage the movement of data in the computer; it manages access to the hardware devices of the computer by application programs. An operating system also manages system services such as memory allocation—the movement of data from various storage devices into RAM where it can be accessed by the CPU, communications with other computers and devices via the network, display of data in text or graphic format on the display, printing, and much more.
In addition, an operating system provides at least some minimal system utility programs for managing various aspects of the system. These utility programs perform functions like deleting files, copying files from one place to another, setting display resolution, and complex processing of textual data.