Batch processing is a technique in which Operating System collects programs and data together in

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OPERATING SYSTEM PROPERTIES Following are few of very important tasks that Operating System

1 Batch Processing Batch processing is a technique in which Operating System collects

Operating system does the following activities related to batch processing. 1.

2. Keeps a number a jobs in memory and executes them without any manual information. 3.

1 OPERATING SYSTEM PROPERTIES Following are few of very important tasks that Operating System handles. 1.1 Batch Processing Batch processing is a technique in which Operating System collects programs and data together in a batch before processing starts. Operating system does the following activities related to batch processing. 1. Defines a job which has predefined sequence of commands, programs and data as a single unit. 2. Keeps a number a jobs in memory and executes them without any manual information. 3. Jobs are processed in the order of submission i.e. first come first served fashion. 4. 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.

2 1. Batch processing takes much of the work of the operator to the computer. 2. Increased performance as a new job gets started as soon as the previous job finished without any manual intervention. Disadvantages 1. Difficult to debug program. 2. A job could enter an infinite loop. 3. Due to lack of protection scheme, one batch job can affect pending jobs. 1.2 Interactivity Interactivity is a technique in which user is capable to interact with computer system. Operating system does the following activities related to interactivity. 1. Provides user an interface to interact with system. 2. Managers input devices to take inputs from the user. For example, keyboard. 3. Manages output devices to show outputs to the user. For example, Monitor. 4. Response time needs to be short since the user submits and waits for the result. 1.3 Multiprogramming Multiprogramming is a technique in which two or more programs reside in memory at the same time. Multiprogramming increases CPU utilization. It ensures that the CPU always has one job to execute. Following figure shows the memory layout for a multiprogramming system: Prof. M. Fahim, , itsfahim@hotmail.com Page 2

I/O operation may take a long time to complete. During this time CPU can be utilized by another process. 5.

3 Operating system does the following activities related to multiprogramming. 1. The operating system keeps several jobs in memory at a time. 2. The operating system picks and begins to execute one of the jobs in the memory. 3. When currently executing job requires an I/O operation, the CPU is switched to the next job in memory. 4. I/O operation may take a long time to complete. During this time CPU can be utilized by another process. 5. Multiprogramming operating system monitors the state of all active programs and system resources. 6. It ensures that the CPU is never idle unless there are no jobs 1. High and efficient CPU utilization. 1. User feels that many programs are allotted CPU almost simultaneously. Disadvantages 1. CPU scheduling is required. Prof. M. Fahim, , itsfahim@hotmail.com Page 3

2. To accommodate many jobs in memory, memory management is required. 1.

Switches occur so frequently that the users may interact with each program while it is running.

Operating System handles multiple operations / executes multiple programs at a time. 5. Multitasking Operating Systems are also known as Time-sharing systems. 6.

4 2. To accommodate many jobs in memory, memory management is required. 1.4 Multitasking Multitasking is a technique in which multiple jobs are executed by the CPU simultaneously. This is done by switching between the jobs. 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. 3. The user gives instructions to the programs and receives an immediate response. 4. Operating System handles multiple operations / executes multiple programs at a time. 5. Multitasking Operating Systems are also known as Time-sharing systems. 6. Each user has at least one separate program in memory. 7. A program that is loaded into memory and is executing is commonly referred to as a process. 8. When a process executes, it typically executes for only a very short time before it either finishes or needs to perform I/O. Prof. M. Fahim, , itsfahim@hotmail.com Page 4

5 9. I/O operation may take a long time to complete. During this time CPU can be utilized by another process. 10. 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. 1. Increases the productivity i.e. more jobs are done in less time. 2. Enables to share the data between different applications. 3. Enables to switch between applications instantly. Disadvantages 1. Complex OS is required. 2. Large main memory is required. 1.5 Multiprocessing Multiprocessing is a technique in which two or more CPUs are used within a single computer system. These CPUs communicate with each other by sharing computer bus, memory and I/O devices. Multiprocessing is also known as Parallel Processing. Operating system does the following activities related to multiprocessing. 1. Divides a process into sub processes. 2. Executes these sub processes in parallel on different CPUs independently. 3. Accomplishes the task by combining results of the sub processes. Generally the parallel processing is used in the fields like artificial intelligence and expert system, image processing, weather forecasting etc. 1. Higher performance due to parallel processing. 2. If one CPU fails, other CPUs are used to perform that CPU s job. Prof. M. Fahim, , itsfahim@hotmail.com Page 5

6 Disadvantages 3. Complex OS is required. 4. Large main memory is required. 5. Very expensive. 1.6 Real Time System A real-time application is an application that responds to certain inputs extremely quickly thousandths or millionths of a second (milliseconds or microseconds, respectively). Real-time applications are needed to run medical diagnostics equipment, life-support systems scientific instruments, and industrial systems. Single-User/Single/T asking Operating Systems Real time systems are usually embedded systems. Operating system does the following activities related to real time system activity. 1. Typically read from and react to sensor data. 2. Must guarantee response to events within fixed periods of time to ensure correct performance. 1.7 Distributed Environment Distributed environment refers to multiple independent CPUs or processors in a computer system. Operating system does the following activities related to distributed environment. 1. Distributes computation logics among several physical processors. 2. The processors do not share memory or a clock. 3. Each processor has its own local memory. 4. OS manages the communications between the processors. They communicate with each other through various communication lines. Prof. M. Fahim, , itsfahim@hotmail.com Page 6

1.8 Spooling Spool: A spool is a temporary storage area (buffer) in the memory or hard disk.

The most common spool is a print spool. It is used to store the print jobs that are sent to the printer.

Therefore, the document may be held in print spool during the warm up process.

Spooling refers to putting data of various I/O jobs in a single buffer.

OS does the following activities related to spooling: 1.

7 1.8 Spooling Spool: A spool is a temporary storage area (buffer) in the memory or hard disk. It is used to store input or output data. it is used to overcome the speed differences of I/O devices. The most common spool is a print spool. It is used to store the print jobs that are sent to the printer. The printer may need to warm up before printing a document. Therefore, the document may be held in print spool during the warm up process. Spooling: Spooling is an acronym for Simultaneous Peripheral Operations On-Line. Spooling refers to putting data of various I/O jobs in a single buffer. This buffer is a special area in memory or hard disk which is accessible to I/O devices. OS does the following activities related to spooling: 1. Handles I/O device data spooling as different devices have different data access rates. 2. Maintains the spooling buffer which provides a waiting station where data can rest while the slower device catches up. 3. Maintains parallel computation because of spooling. As a computer can perform I/O in parallel fashion. It becomes possible to have the computer read data from a tape, write data to disk and to write out to a tape printer while it is doing its computing task. Prof. M. Fahim, , itsfahim@hotmail.com Page 7

8 4. The spooling operation uses a disk as very large buffer. 5. Spooling is capable of overlapping. It enables to perform I/O operation for one job and at the same time processor operations for another job. Prof. M. Fahim, , itsfahim@hotmail.com Page 8

UNIT 1 JAGANNATH UNIVERSITY UNIT 2. Define Operating system and its functions. Explain different types of Operating System

UNIT 1 JAGANNATH UNIVERSITY UNIT 2. Define Operating system and its functions. Explain different types of Operating System JAGANNATH UNIVERSITY BCAII OPERATING SYSTEM MODEL TEST PAPER (SOLVED) UNIT 1 Q1 Q2 Q3 Q4 Q5 Define Operating system and its functions Explain different types of Operating System Describe different types