Skip to main content

First-come, First-served Scheduling-computer world

 First-come, First-served Scheduling

In this scheduling algorithm simply the jobs according to their arrival time which job come first in the queue will get the CPU first. It means the process(job) that requests the CPU first is allocate the CPU first. The FCFS policy is simply and easily managed with a FIFO(First in First out) queue. When a process enter in the ready, its PCB is linked onto the tail of the queue. When the CPU is free, it allocated to the process at the head if the queue. The code for FCFS scheduling is very simple to understand. On the negative side, the average waiting time under the FCFS policy is long. The CPU has been allocated to a process, that process keeps CPU its processing is not complete. So the CPU in this scheme is scheduled to the process in the order of arrival at the ready queue it is the simplest CPU scheduling algorithm. 

1. Turn around time :

Turn around time is the time taken by a process between ready queue and finishing execution.

2. Wait time : 

Wait time is the time when a process wait before it's start execution.

3. Burst time: 

Burst time is that time which is taken by a process for its execution on the CPU.

Process P1, P2, P3 it's burst time is in the order 24, 3, 3

If the processes arrive in the order P1, P2, P3 and served in FCFS order. The waiting time for P1 is 0 millisecond, 24 millisecond for process P2, 27 millisecond for process P3. Thus the average waiting time is (0+24+27)/3=17 milliseconds.


Comments

Post a Comment

Popular posts from this blog

Deadlock in operating system-computer world

  Deadlock in operating system-computer world Deadlock :  In a multi-programming environment, many process may complete for a minute number of resources. A process make a request for a resource and if the resource is not available at that time, the process enter In a waiting state. A waiting state process is never again-able to change state because the resource it has requested is held by other waiting process. This situation is called deadlock. So we can say that a process is said to be deadlock when it is waiting for an event or resources which will never occurs.   so we can say that in this situation none of the process gets executed  since the resource it needs, is held by some other process which is also waits for some other resource to be released.  Let's assume that there are three process P1, P2, p3 and three different resources R1, R2 and R3. R1 is assigned to p1, R2 is assigned to P2 and R3 is assigned to P3.   After somet...
9 comments
Read more

What is sound card, video card, TV tuner card and network adapter card-computer world

 What is sound card, video card, TV tuner card and network adapter card Sound card :  Sound card is also known as audio card, sound sound board or audio output device. Sound card is a expansion card that provide the input and output of audio signals to and from a computer under control of computer programs. It is an expansion card for producing sound on computer that can be heard by speakers and headphones.  Uses of sound card :  Sound card is used for for providing the audio component  for multimedia application such as video auditing , audio auditing .It is also used in the field of education.  Video card :  It is an expansion card that connect to a computer motherboard. Video card is also known as video adapter or video controller. It is used to create a picture on display. TV tuner card : A  TV tuner card is like a television tuner that allow single to be received by a computer. TV tuner c...
2 comments
Read more

Memory management in operating system-computer world

Memory management in operating system-computer world Memory management :   The function of operating system which manages the memory of a computer for the processing of the program this management is known as memory management. There are several programs that consist in memory, so it became to move programs and data around the memory of a memory management system is the collection of hardware and software procedures for the Managing various program consisting in the memory. Memory management play an important role in operating system to improve the speed speed of the computer system.   Memory management determines how  memory is allocated between the processes,  deciding which gets memory, when they receive it and how much they are allowed. When memory is allocated it determines which memory location will be assigned. Main memory refers to a physical memory that is the internal memory of the computer. Main memory is also known as RAM. The computer is able t...
1 comment
Read more