• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Processor Scheduling

Extracts from this document...


Assignment 3 Operating Systems Task 2 Introduction In this assignment we shall be looking at the four main memory management functions of an operating system. They are Process Management, Main-memory management, File and Disk management and Input/Output memory management. They shall be looked at further and in more detail within the task 3 section of the assignment. Process Management Scheduling Techniques There are three main states within the process management sub system. They are waiting, ready and running. Each process is started with the operation of system calls. Above can be seen a diagram of the scheduling operations within a system. The job queue is full of processes waiting to be entered into the ready queue, but must pass through admission to do so. When the job enters the ready queue it must wait for the processor to continue its processing method until it is time for the job to be dispatched. When dispatched it will enter the CPU where it will be executed. However, there are two errors that may occur. ...read more.


Looking at the figures above it comes as no surprise that this method is rarely used in a day to day environment. Shortest Job First The processor will execute each job in order of the completion time from lowest to highest. However; the first job received in the processor will be executed first even if it's bigger than any of the others in the queue. This method can reduce time and is far more efficient than FCFS. It can only work though if the CPU is aware if each processes burst time and then when this is achieved order can be obtained. This is a form of processing scheduling which has the lowest average waiting time using its algorithm. It's also a very clever processing technique. The processor cannot actually define the burst times individually so the operating system takes into account the previous burst times and then makes an average. This is a very clever feature. Process Arrival Time Burst Time P1 0 7 P2 2 4 P3 4 1 P4 5 4 0 7 8 12 16 Average waiting time = (0 + 6 +2 +7) ...read more.


When exceeded, the process shall be placed at the back of the queue and will be given an interrupt. It can be said that the round robin technique is a fair one. * If there are n processes in the ready queue and the time quantum is q then each process gets 1/nth of the CPU. * No process waits more than (n-1)q time units before receiving CPU allocation * It typically has a higher turnaround time than SRTF but a better average response time. The table below works on the basis of a time quantum of 4ms. Process Burst P1 24 P2 3 P3 3 0 4 7 10 14 18 22 26 30 Above can be seen a time quantum dictating the length of a process in the CPU. It can be said for definite that the process cannot exceed the quantum even if their are no other processes in the queue. We can also see that the P1 uses a whole time quantum; P2 and P3 however only use a part of it. P1 waits 0 + 6 = 6, P2 waits for 4 and P3 waits for 7 Average time = (6 + 4 + 7) / 3 = 5.66ms ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Computer Science section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Computer Science essays

  1. Peer reviewed

    information systems assignment 2

    4 star(s)

    usually as data which is being searched and analyzed to find different patterns, relationships and correlations between statistical information. Using computers to access databases it is easier to collect information and data which can then be analysed systematically, this uses advanced techniques to search for relationships.

  2. Free essay

    Hardware and Functions of a Micro Processor

    It is important to remember tat computers only work in values of zeroes and ones, zero representing low voltage and one representing high voltage. To make the computer system function, by processing useful information these binary values need to be converted in to meaningful logic.

  1. The CPU (Central Processing Unit) is the processor within the computer

    Storage Devices - CD ROM CD ROMs store a large amount of data. Most computer games are now purchased on CD ROMs. Data is stored optically which means that it is read by using a laser. The CD ROM is placed inside a drive and the disc rotates at high speed.

  2. Programming Techniques

    Long programs that are split into modules are easier to read, debug and maintain (4) A team of programmers can each work on separate modules, thus shortening the total development time for a large project and each one contributing its own specialism (5)

  1. What is transaction processing?

    The information resulting from a query can be sorted into ascending or descending order on a particular field. Reports can be used to organise and present information from the database table(s). This data can be designed to group information in specific categories, produce summaries and calculation etc.

  2. Batch Processing

    Processing Add new record Use details in transaction file record to insert a new record into the new master file at the correct position in the file. Delete record Do not copy the record that is to be deleted from the master file to the new master file.

  1. Smart Card System

    The main challenges of their job were to create a computer language that could be used to build programs that would run in fundamentally different execution platform ands environments. Because these machines provide a wide variety of hardware and software environments, it was necessary that Java be Platform-independent.

  2. CP3 - Proposed Solution to a Realistic Problem - Apartment Administration software

    End the use of the file END; Loadfromfile; END; procedure Saverecord; begin IF FormCustomers.EDfirstname.text <> '' THEN // Only save record if there is data in the firstname field with FormCustomers do // Associate the procedure with the form with customerlist[pos] do // Select the record from the bookings array

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work