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1.1.2 Describe Various Types Of Operating Systems

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1.1.2 Describe Various Types Of Operating Systems

Batch operating system    


  • The users of batch operating system do not interact with the computer directly. Each user prepares his job on an off-line device like punch cards and submits it to the computer operator. 
  • To speed up processing, jobs with similar needs are batched together and run as a group. Thus, the programmers left their programs with the operator.
  • The operator then sorts programs into batches with similar requirements.
  • The problems with Batch Systems are following.
    • Lack of interaction between the user and job.
    • CPU is often idle, because the speeds of the mechanical I/O devices is slower than CPU.
    • Difficult to provide the desired priority.

Batch System

Multiprogramming operating system


  • A multi programming operating system is one that allows end-users to run more than one program at a time. The development of such a system, the first type to allow this functionality, was a major step in the development of sophisticated computers. 
  • The technology works by allowing the central processing unit (CPU) of a computer to switch between two or more running tasks when the CPU is idle.
  • Early computers were largely dedicated to executing one program — or, more accurately, one task initiated by a program — at a time. Understanding the concept of tasks is key to understanding how a multi programming operating system functions. A "task" is a small sequence of commands that, when combined, comprises the execution of a running program. For example, if the program is a calculator, one task of the program would be recording the numbers being input by the end-user.
  • A multi programming operating system acts by analyzing the current CPU activity in the computer. When the CPU is idle — when it is between tasks — it has the opportunity to use that downtime to run tasks for another program. In this way, the functions of several programs may be executed sequentially. For example, when the CPU is waiting for the end-user to enter numbers to be calculated, instead of being entirely idle, it may run load the components of a web page the user is accessing.


Multiprogramming

Time Sharing

  • Time sharing is a technique which enables many people, located at various terminals, to use a particular computer system at the same time. 
  • Time-sharing or multitasking is a logical extension of multi-programming.
  • Processor's time which is shared among multiple users simultaneously is termed as time-sharing. The main difference between Multiprogrammed Batch Systems and Time-Sharing Systems is that in case of Multiprogrammed batch systems, objective is to maximize processor use, whereas in Time-Sharing Systems objective is to minimize response time.
  • Multiple jobs are executed by the CPU by switching between them, but the switches occur so frequently. Thus, the user can receives an immediate response. For example, in a transaction processing, processor execute each user program in a short burst or quantum of computation. That is if n users are present, each user can get time quantum. When the user submits the command, the response time is in few seconds at most.
  • Operating system uses CPU scheduling and multiprogramming to provide each user with a small portion of a time. Computer systems that were designed primarily as batch systems have been modified to time-sharing systems.
  • Advantages of Timesharing operating systems are following
    • Provide advantage of quick response.
    • Avoids duplication of software.
    • Reduces CPU idle time.
  • Disadvantages of Timesharing operating systems are following.
    • Problem of reliability.
    • Question of security and integrity of user programs and data.
  • Problem of data communication.

Distributed operating system


  • A distributed operating system is a software over a collection of independent, networked, communicating, and physically separate computational nodes. Each individual node holds a specific software subset of the global aggregate operating system. 
  • Each subset is a composite of two distinct service provisioners. The first is a ubiquitous minimal kernel, or micro kernel, that directly controls that node’s hardware. 
  • Second is a higher-level collection of system management components that coordinate the node's individual and collaborative activities. These components abstract micro kernel functions and support user applications.
  • The advantages of distributed systems are following.
    • With resource sharing facility user at one site may be able to use the resources available at another.
    • Speedup the exchange of data with one another via electronic mail.
    • If one site fails in a distributed system, the remaining sites can potentially continue operating.
    • Better service to the customers.
    • Reduction of the load on the host computer.
    • Reduction of delays in data processing.

Distributed
Sources : http://www.tutorialspoint.com/operating_system/os_types.htm
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