An operating system acts as an interface between the computer hardware and the user. It is system software which runs on the computer, as soon as the computer is switched on. It brings the computer in to operating condition that is it makes the computer ready to be used by the programmer. This process is called Booting.

The operating system monitors and controls the execution of program entered through the input device. The operating system makes the control unit to load and execute the appropriate compiler. If the user requires printing the answer (or) result on the printer, operating system software should direct that output to the appropriate printer.

The combination or collection of routines to read data, load compiler, load and initiate execution of program, control the output and monitor, the completion of job is called the operating system. This operating system provides an interface between the computer hardware and the programmer [user] that simplifies and makes feasible the creation, coding, debugging and maintenance of application programs.

  •  Easy interaction between users and computers.
  •  It provides access to compilers to translate programs from high level language to machine language [low  level language].
  •  It controls input, output and program execution.
  •  It provides long term storage of user information in the form of files.
  •  It manages the usage of main memory.


The types of operating systems are classified in to the following types. Consider them

  •  Batch operating system.
  •  Distributed operating system.
  •  Multi-programming operating system
  •  On-line operating system
  •  Real-time operating system and
  •  Time sharing operating system

Consider each of them in detail….

Batch operating system:

In this Batch operating system environment, the tasks (or) programs to be executed are grouped together as a queue to be considered as a batch by the operating system. The data required by each program for processing are gathered and submitted along with the batch of the programs. Each program consists of two statements “Program-Begin” and “Program-End”. After compiling and executing the first program the operating system automatically starts the compilation of the second program and executes it with necessary data and produces the result (or) output, and then continues with the third task and so on until the assigned tasks are executed.

Distributed Operating system:

The standalone computers are interconnected to form a computer network so that they can use all the computer resources like printer, scanner, CD-drive etc in an efficient manner. The processing in a distributed system are in either centralized (or) decentralized.

In a centralized environment, files and data are mainly stored in a central computer. To perform a task each computer has to request the central computer for files and data to process and produce the results.

In decentralized processing, a local computer processes the data and produces the results.

 Multiprogramming operating system:

It allows the processing of two (or) more tasks [programs] at the same time. This is possible in a multi processing system. Multiprogramming means that there are more than one processor operating on the same memory but executing different processes simultaneously.

On-line operating system:

It provides interactive computations. In such systems, delays in processing user requests are minimized. Files of users are available “on-line” in disk and may be retrieved immediately. Large disk storage in the system makes it convenient to store large volumes of data and to retrieve them fast.

Real-time operating system:

In this environment, the data processing rate must be higher that the incoming data speed. Computer is employed to control the operations (or) working of a physical system.

Time sharing operating system:

Multi-programming is a kind of time sharing of the CPU and memory. Time sharing operating system permits many individual users to interact with the system. In such a manager, that the system appeared dedicated to each user. This is possible because computer is a very fast machine and can execute millions of instructions in one second. Hence, the number of jobs processed by the computer in a given period is maximized. This is known as maximizing the computers throughout.