types of os

Types of operating system

Q1. Types of operating system?

There are so many types of operating system in market here we will discuss about some of them.

       I.            Simple batch system

     II.            Multiprogramming batch system

  III.            Multi-user system

  IV.            Multiprocessing system

    V.            Multi-tasking system

  VI.            Multi-threading

VII.            Real time operating system

VIII.            Time sharing operating system

  IX.            Distributed operating system

    X.            Network operating system

Q2. Explain simple batch system with advantage and disadvantage?

·        Batch processing is a technique in which Operating System collects one programs and data together in a batch before processing starts. Operating system does the following activities related to batch processing.

ü OS defines a job which has predefined sequence of commands, programs and data as a single unit.

ü OS keeps a number a jobs in memory and executes them without any manual information.

ü Jobs are processed in the order of submission i.e. first come first served fashion.

ü When job completes its execution, its memory is released and the output for the job gets copied into an output spool for later printing or processing

·        Simple batch system is a type of system in which there is no direct intraction between user and the computer.

·        The user has to submit a job (written on a card/tape) to a computer operation.

Ø Advantage

·         Batch processing takes much of the work of the operator to the computer.

·        Increased performance as a new job gets started as soon as the previous job finished without any manual intervention.

Ø Disadvantage

·        Difficult to debug program.

·         A job could enter an infinite loop.

·         Due to lack of protection scheme, one batch job can affect pending jobs.

·        Zero interaction between computer and user.

·        No machine mechanism to prioritize process.

Q2.Explain Multiprogramming batch system with advantage and disadvantage?

·        When two or more programs are residing in memory at the same time, then sharing the processor is referred to the multiprogramming. Multiprogramming assumes a single shared processor. Multiprogramming increases CPU utilization by organizing jobs so that the CPU always has one to execute.

Following figure shows the memory layout for a multiprogramming system.

·        Once the job need input output operation operating system switches to another job cpu and operating system always busy .

·        if several job are ready to run at the same time then system choose which one to run(cpu scheduling)

Operating system does the following activities related to multiprogramming

·        The operating system keeps several jobs in memory at a time.

·        This set of jobs is a subset of the jobs kept in the job pool.

·        The operating system picks and begins to execute one of the job in the memory.

·        Multiprogramming operating system monitors the state of all active programs and system resources using memory management programs to ensures that the CPU is never idle unless there are no jobs

Ø Advantage

·        High and efficient CPU utilization.

·        User feels that many programs are allotted CPU almost simultaneously

Ø Disadvantage

·        CPU scheduling is required.

·        To accommodate many jobs in memory, memory management is required.

Q3. Explain multiuser system with advantage and disadvantage?

·        A multiuser operating system allows for multiple user to use the same computer at the same time and different time example linux unix windows 2000.

Ø Advantage

·        More than one person can use a single computer.

·        Multiple user can share the data to each other.

Ø Disadvantage

Q4. Explain Multiprocessing operating system with advantage and disadvantage?

·        An operating system is capable of supporting and utilizing more than one computer processor . Example linux unix win xp.

·        A multiprocessor system consists of several processor that share a common physical memory. it provide higher computing power speed.

·        In it all processor operate under operating system.

Ø Advantage

·        Enhance performance.

·        Execution of several task by different processor, concurrently increase the system through put without speeding up the execution of single task.

·        If possible system divide task into many subtask and then these sub task can be execution in parallel in different processor there by speeding up execution of single task .

 Q5. Explain multitasking operating system with advantage and disadvantage?

·        An operating system that is capable of allowing multiple software process to run at the same time. Example linux, unix, windows etc.

·        Multitasking refers to term where multiple jobs are executed by the CPU simultaneously by switching between them. Switches occur so frequently that the users may interact with each program while it is running. Operating system does the following activities related to multitasking.

·        The user gives instructions to the operating system or to a program directly, and receives an immediate response.

·         Operating System handles multitasking in the way that it can handle multiple operations / executes multiple programs at a time.

·         Multitasking Operating Systems are also known as Time-sharing systems.

·         These Operating Systems were developed to provide interactive use of a computer system at a reasonable cost.

·         A time-shared operating system uses concept of CPU scheduling and multiprogramming to provide each user with a small portion of a time-shared CPU.

·         Each user has at least one separate program in memory.

·        A program that is loaded into memory and is executing is commonly referred to as a process.

·        When a process executes, it typically executes for only a very short time before it either finishes or needs to perform I/O.

·         Since interactive I/O typically runs at people speeds, it may take a long time to complete. During this time a CPU can be utilized by another process.

·         Operating system allows the users to share the computer simultaneously. Since each action or command in a time-shared system tends to be short, only a little CPU time is needed for each user.

·         As the system switches CPU rapidly from one user/program to the next, each user is given the impression that he/she has his/her own CPU, whereas actually one CPU is being shared among many users.

Q6. Explain Multi threading  operating system ?

·        An operating system that allows different part of software program to run concurrently.

·        Example linux unix

·        Some operating system provides a combined user level thread and Kernel level thread facility. Solaris is a good example of this combined approach. In a combined system, multiple threads within the same application can run in parallel on multiple processors and a blocking system call need not block the entire process.

·         Multithreading models are three types

ü Many to many relationship.

ü Many to one relationship.

ü  One to one relationship.

·        Many to Many Model

·        In this model, many user level threads multiplexes to the Kernel thread of smaller or equal numbers. The number of Kernel threads may be specific to either a particular application or a particular machine.

·        Following diagram shows the many to many model. In this model, developers can create as many user threads as necessary and the corresponding Kernel threads can run in parallels on a multiprocessor.

·        Many to One Model

·        Many to one model maps many user level threads to one Kernel level thread. Thread management is done in user space. When thread makes a blocking system call, the entire process will be blocks. Only one thread can access the Kernel at a time, so multiple threads are unable to run in parallel on multiprocessors.

·         If the user level thread libraries are implemented in the operating system in such a way that system does not support them then Kernel threads use the many to one relationship modes.

·        One to One Model

·        There is one to one relationship of user level thread to the kernel level thread. This model provides more concurrency than the many to one model. It also another thread to run when a thread makes a blocking system call. It support multiple thread to execute in parallel on microprocessors.

·        Disadvantage of this model is that creating user thread requires the corresponding Kernel thread. OS/2, Windows NT and windows 2000 use one to one relationship model.

Q7. Explain real time operating system advantage and disadvantage  ?

·        An operating system known to give maximum time for each of the critical operation that it performs like operating system calls and interrupt handling .

·        Real time system is defines as a data processing system in which the time interval required to process and respond to inputs is so small that it controls the environment. Real time processing is always on line whereas on line system need not be real time. The time taken by the system to respond to an input and display of required updated information is termed as response time. So in this method response time is very less as compared to the online processing.

·        Real-time systems are used when there are rigid time requirements on the operation of a processor or the flow of data and real-time systems can be used as a control device in a dedicated application. Real-time operating system has well-defined, fixed time constraints otherwise system will fail. For example Scientific experiments, medical imaging systems, industrial control systems, weapon systems, robots, and home-appliance controllers, Air traffic control system etc.

There are two types of real-time operating systems.

·        Hard real time operating system

ü The real time operating system which guarantee the maximum time for critical operation and complete them on time known as hard real time operating system.

ü Hard real-time systems guarantee that critical tasks complete on time. In hard real-time systems secondary storage is limited or missing with data stored in ROM. In these systems virtual memory is almost never found.

ü These system are known as HROTS.

·        Soft real time operating system

ü The real time operating system that can only guarantee a maximum of the time i.e. the critical task will get priority over other task but no assured of completing it in defined time.

ü Soft real time systems are less restrictive. Critical real-time task gets priority over other tasks and retains the priority until it completes. Soft real-time systems have limited utility than hard real-time systems. For example, Multimedia, virtual reality, Advanced Scientific Projects like undersea exploration and planetary rovers etc.

ü These systems are known as SROTS.

Q8. Explain time sharing operating system?

·        Very similar to multiprogramming operating system.

·        In time sharing operating system the prime focus is on minimizing the response time while in multiprogramming the prime focus is to maximize the CPU usage.

·        Time-sharing operating systems have no long term scheduler. When process changes the state from new to ready, then there is use of long term scheduler.

·        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 multiprogramming. Processor's time which is shared among multiple users simultaneously is termed as time-sharing. The main difference between Multi programmed Batch Systems and Time-Sharing Systems is that in case of multi programmed 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 receive 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.

·        Advantage

ü Provide advantage of quick response.

ü Avoids duplication of software.

ü Reduces CPU idle time.

·        Disadvantage

ü Problem of reliability.

ü  Question of security and integrity of user programs and data.

ü Problem of data communication

Q9. Distributed operating system?

·        The motivation behind developing distributed operating system is the ability of power full and inexpensive microprocessor and advances in communication technology.

·        These advancement in technology have many computers that are interconnected by communication networks.

·        The main benefit of distributed operating system is its low price and performance ratio .

·        Advantage

ü Speedup the exchange of data with one another via electronic mail.

ü If one site fails in a distributed system, the remaining sites can potentially continue operating.

ü Better service to the customers.

ü Reduction of the load on the host computer.

ü  Reduction of delays in data processing

ü Fast processing

ü Less load on host machine.

Q10. Network operating system?

·        Network Operating System runs on a server and provides server the capability to manage data, users, groups, security, applications, and other networking functions. The primary purpose of the network operating system is to allow shared file and printer access among multiple computers in a network, typically a local area network (LAN), a private network or to other networks. Examples of network operating systems are Microsoft Windows Server 2003, Microsoft Windows Server 2008, UNIX, Linux, Mac OS X, Novell NetWare, and BSD.

·        Advantage

ü Centralized servers are highly stable.

ü Security is server managed.

ü  Upgrades to new technologies and hardware can be easily integrated into the system.

ü  Remote access to servers is possible from different locations and types of system.

·        Disadvantage

·          

·        High cost of buying and running a server.

·        Dependency on a central location for most operations.

·        Regular maintenance and updates are required.