An operating system (commonly abbreviated OS and O/S) is the software component of a computer system that is responsible for the management and coordination of activities and the sharing of the limited resources of the computer.

There are 4 types of operating system which is explained below:-

i. Batch Operating System:-A batch system is one in which jobs are bundled together with the instructions necessary to allow them to be processed without intervention. The basic physical layout of the memory of a batch job computer is shown below:

Monitor (permanently resident)
User Space
(compilers, programs, data, etc.)

The monitor is system software that is responsible for interpreting and carrying out the instructions in the batch jobs. When the monitor starts a job, the entire computer is dedicated to the job, which then controlls the computer until it finishes.

1. Advantages of batch systems move much of the work of the operator to the computer
increased performance since it was possible for job to start as soon as the previous job finished
2. Disadvantages turn-around time can be large from user standpoint
more difficult to debug program
due to lack of protection scheme, one batch job can affect pending jobs (read too many cards, etc)
a job could corrupt the monitor, thus affecting pending jobs
a job could enter an infinite loop

ii. Multiprogramming Operating System:- As machines with more and more memory became available, it was possible to extend the idea of multiprogramming (or multiprocessing) as used in spooling batch systems to create systems that would load several jobs into memory at once and cycle through them in some order, working on each one for a specified period of time. There are different type of Multiprogramming Operating System, some main stream are discussed below:-

a. Multitasking Operating System:- A running state of a program is called a process or a task.multitasking allows the computer system to more reliably guarantee each process a regular "slice" of operating time. It also allows the system to rapidly deal with important external events like incoming data, which might require the immediate attention of one or another process. So, multitasking operating system is a type of multiprogramming operating system which can perform several process simultaneously.The earliest multitasking OS available to home users was the AmigaOS. All current major operating system support this feature.

b. Multi-user Operating System:- A multi-user operating system allows for multiple users to use the same computer at the same time and/or different times. Linux,Unix,Windows OS are some example of multitasking operating system.

c. Multiprocessing Operating System:- An operating system capable of supporting and utilizing more than one computer processor.Linux,Unix,Windows OS are some example of multitasking operating system.

d. Real Time Operating System:- It is an OS where there are a number of possibly unrelated external activities needed to be controlled by a single processor system. In such systems a hierarchical interrupt system was coupled with process prioritization to ensure that key activities were given a greater share of available process time.

iii. Network Operating System:- A network operating system (NOS) is software that controls a network and its message (e.g. packet) traffic and queues, controls access by multiple users to network resources such as files, and provides for certain administrative functions, including security.

The upper 5 layers of the OSI Reference Model provide the foundation upon which many network operating systems are based. 6WINDGate,Cisco IOS,BSD are some of the example of NOS.

iv. Distributed Operating System:- Distributed systems are very much like traditional operating systems. First, they act as resource managers for the underlying hardware, allowing multiple users and applications to share resources such as CPUs, memories, peripheral devices, the network, and data of all kinds. Second, and perhaps more important, is that distributed systems attempt to hide the intricacies and heterogeneous nature of the underlying hardware
by providing a virtual machine on which applications can be easily executed.

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