2.  Introduction to Operating System Introduction to Operating System  Types Of An Operating System Types Of An Operating System  Single User Single User  Multi User Multi User  Classification of Operating System Classification of Operating System  Early O.S. Or Processing O.S. Early O.S. Or Processing O.S.  Batch O.S. Batch O.S.  Multi Programming O.S. Multi Programming O.S.  DIAGRAM OF MULTIPROGRAMMING DIAGRAM OF MULTIPROGRAMMING  Time Sharing Time Sharing  Multiprocessing or Parallel Processing O.S. Multiprocessing or Parallel Processing O.S.  DIAGRAM OF MULTIPROCESSING DIAGRAM OF MULTIPROCESSING  Advantages and Disadvantages Multiprocessing or Parallel... Advantages and Disadvantages Multiprocessing or Parallel...  Multitasking Multitasking  DIAGRAM OF MULTITASKING DIAGRAM OF MULTITASKING  Distributed Operating System Distributed Operating System

3.  A program that controls the execution of application programs.  An operating system (OS) is the software that manages the sharing of the resources of a computer and provides programmers with an interface used to access those resources.  Examples: MS-Windows, Linux, Unix, Solaris, Mac OS, MS-DOS, Windows/NT etc. Back

4.  There are two types of Operating System. 1 Single User Operating System. 2. Multi User Operating System. Back

5.  In this kind of system the processor or a computer does only one job at a time. That is at one point of time only one task can be performed. For Example : MS-DOS. Back

6.  This type of system is used by more than one user. It allows the interaction of one user with other. It also helps in executing more than one task at a particular time. For Example: Unix and Windows NT. Back

7.  Early O.S. Or Processing O.S.  Batch O.S.  Interactive O.S.  Real Time O.S.  Multiprogramming O.S.  Timesharing O.S.  Multiprocessing O.S.  Multitasking O.S.  Distributed O.S. Back

8.  In serial processing operating system only one job resides in computer memory And it remains there till it is executed. After completion of job, next job is entered In serial fashion. In this system, memory management is very simple because whole memory space is allocated to the job or program.  Advantages: 1. Resource Management is Very Easy. 2. Resource Allocation is Very Easy.  Disadvantages: 1.CPU remains Ideal most of the time. 2. Very Slow. 3. Waiting time of jobs are more. Back

9.  The user of batch operating system do not allow to interact the computer Directly. Each user prepares his job on an off-line device like punch cards and submits it to the computer operator. The operator sorts jobs in to batches with similar requirements and runs each batch On the computer. When the jobs is completes its output is sent back to the Appropriate user. In batch system, major task of operation system is to transfer Control automatically from one job to the next.  Advantages: 1.Resource Management and Allocation is very easy. 2.Faster than serial Processing.  Disadvantages: 1.Lack of interaction between the user and the job while job is executing. 2.Utilization of CPU is very poor. 3.The CPU is often Idle. 4.Difficult to provide the desired priority. Back

10.  Multiprogramming refers to keeping several programs in different parts of the main Memory at the same time and executing them concurrently.  The CPU switches from One program to another almost instantaneously. Since the operating speed of CPU is Much faster than that of I/O operations, the CPU can allocate time to several programs instead of remaining idle when one is busy the I/O operations.  Hence,in Multiprogramming system, when one program is waiting for I/O transfer, there is Another program ready to use the CPU. Back

12.  This is a technique which enables many people, located at various terminals, to use a particular computer system at the same time. Each user is actually Away from the computer and other uses. Each user has its own programs. Time sharing system, allocates a very short period of CPU time one-by-one to each user process, Beginning from the first user process and proceeding through the last one, and then Again beginning from the first one. The short period of time during which a user process gets the attention of the CPU is known as A TIME SLICE, TIME SLOT, OR QUANTUM, and is typically of the order of 10 to 100 millisecond. Thus Timesharing may be viewed as a multi-use multiprogramming technique.  Advantages: 1. Reduce CPU idle time. 2. Provides advantages of quick response  Disadvantages: 1. Problem of data communication. 2. Question of security and integrity of user programs and data. Back

13.  This technique consist of two or more CPUs connected to common peripherals.  Instruction from different programs may either be processed by different CPUs or one, or more,processor may be execute instruction from the same program Simultaneously.  This technique can serve a purpose only in large computer installations, where same jobs are too large for one CPU, or where a large number of Problems need to be solved simultaneously. Back

15.  Advantages of Multi processing: 1.Better throughput: It improves the performance of computer system by allowing parallel processing of segments of programs. 2. Better Reliability: It provides a built-in backup. If one of the CPUs breaks down, the other CPUs automatically takes over the complete workload until repairs are made. Hence, Multiprocessor system have better reliability. Saving Cost: Such system shares the memory, buses, clock etc. So it reduce the cost of the system.  Disadvantages of Multi processing: 1. A large main memory is required. 2. A very sophisticated operating system is required to schedule, balance and co-ordinate the input, output and processing activities of multiple CPUs. 3. Such System are very expensive. Back

16.  In multiuser systems, multitasking is the same as multiprogramming.  In a single user system, it is not Necessary that the system work only on one job at a time.  In fact, a user of a single-user system often has multiple tasks concurrently processed by the system. In multitasking several programs resides in RAM together and executed Simultaneously.  In multitasking, the computer might be printing out a data file while at the same time the user is running a word processing program to enter a document.  When Task 1 is interrupted,Task 2 is Performed.Task 2 is completed Task 1 is Resumed Back

18.  In distributed operating systems, the user access remote resources in the same way as the local resource and Accessed. Distributed operating systems are based on two modes: 1.Client server model In this model, the client send a request for a resource to the server and the server, In turn, Provides the requested resource as a response back to the client. 2.Peer-to-peer model In a peer-to-peer model, all the computers behave as peers as well as clients. These peers communicate with each other for exchange of their resources Back