Types of Operating System - Operating System Definition - OS

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Types of Operating System

Batch processing operating system: 

Batch processing system is the type of operating system which collects jobs in batches before being processed by the CPU. A job is piece of work usually consisting of a program and the data to be Run. until start the processing by computer all the jobs are stored in job queues.

Once the CPU gets ready and fetches a job from the job queue, then there is no interaction of the user with the computer to interrupt the processing of the job until its completion.

Batches of jobs are formed by collecting jobs during working hours and then executed during the evening time or at the end of each day or whenever the computer is available. Once a batch job is beginning, it running until it is completed or error. The example of batch processing operating system is IBM's OS 360.

Multi-tasking operating system:

Multitasking is the process in which the operating system performs multiple tasks simultaneously on a single processor in such a way that creates the impression of parallel executions. practically, all modern OS has the ability of multitasking.

Multitasking does not mean that the Computer has multiple processes to execute multiple processes simultaneously. it means that the operating system switches the jobs so quickly on a single processor that the user thinks all these processes are executed in parallel.

Multitasking can be either preemptive or Cooperative. In preemptive version, the operating system divide the CPU time and allocates one slot to each of the programs. Operating systems that support preemptive multitasking are: Solaris, Unix, Windows 2000, windows XP, MacOS X and LINUX. operating system that support cooperative multitasking is windows 3.x.

Real Time operating system:

Real time operating systems are those operating system which give quick response to users requests without delaying them. Unlike batch processing operating systems, real time operating systems reduce immediate response to users request as they are input to the system. Real Time operating system success rate is not only measured incorrectness terms of logically computed result, but also on the basis of time at which the results are produced. As these systems process the user input immediately, therefore, the systems support high degree of interactivity as a result they can be widely used in critical environments, such as, airplane ways control systems and air base system etc.

As the results of real time operating systems are time-based, therefore they are grouped into hard-real time operating systems and soft-real time operating systems. Hard-real time operating system is performing the solution in the specified time constraint with guarantee; otherwise, the results are catastrophic such as flight navigation, automobile, and spacecraft systems.

Features of real time operating system:

1. A real time operating system guarantees a solution or results within a specific time. 
2. These are multitasking Operating systems. 
3. These operating systems are used for the execution of real-time applications, such as weather forecasting, geographical information retrieval, controlling machinery, scientific instruments and industrial systems etc.
4. These systems are aimed on quick and predictable response to events.
5. When these systems start execution of a task, they do not provide full control to the user to interact are interface in that processing.

Parallel processing operating system:

An operating system that operate, control and manage a parallel computer is called parallel processing operating system. A parallel computer system is a computer which has multiple processors that work Cooperative to solve specific computational problem. The parallels execution can be achieved by executing multiple processes on different processors in parallel. Parallel operating systems are much similar to multiprocessing operating system.

Parallel processing operating system is used for problems which need some calculations simultaneously. This task is accomplished by dividing the computationally complex and large problems into smaller and dependent tasks which are executed concurrently on parallel processes.

Parallel processing can get at different levels such as, bit-level, instruction-level, data-level and task-level. UNIX and Microsoft Windows NT are the most commonly used parallel processing operating systems.

 Distributed operating system:

A distributed operating system is an operating system that manage a group of independent computers and make them appear to the users as a single computer.

When independent computers are networked together in such a way to work in a Cooperative manner when they give rise to a distributed system. In a distributed environment, for performing a task, the computers communicate with each other and perform operations in such a way that the user do not feel that the computation are taking place on more than one machine. In a distributed environment, the resources should be shared; the processes should be scheduled on different machines, and the communication and synchronization machine isms should be defined clearly. All these are the duties of a distributed operating system. The distributed operating system hides from the users that where a particular resource is, how the data is accessed, how a resource was moved to a new location and how the error was recovered.

 Advantage of distributed system:

1. Communication and resource sharing is possible which eliminates the need of dedicated resources with each computer system.
2. The system is reliable due to availability of multiple machines for performing the task of failed system.
3. The system has the potential for incremental growth. 

Disadvantage of distributed system:

1. Network connectivity is an essential part of a distributed system which is a difficult and expensive task.
2. Security and privacy is an issue.

Embedded operating system:

Embedded operating systems are designed for use in embedded computer systems. An embedded computer is a computer that is part of another system such as robot, missile etc.

These operating systems are designed for the operations of small machines for example Personal Digital Assistant with low autonomy. They can operate with Limited number of resources. These operating systems are very compact in size and efficient in performance by design. Window CE, embedded Linux and Android are the examples of embedded operating systems.