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

Single partition allocation, Multiple-partition allocation and Fixed Equal-size partitions in operating system-computer world

  Single partition allocation, Multiple-partition allocation and Fixed Equal-size partitions in operating system Single partition allocation In this scheme operating system is residing in law memory and user process are executing in higher memory. Advantages It is simple  It is easy to understand and use Disadvantages User job is limited to the size of available memory. It leads to poor Utilization of processor and memory. Multiple-partition allocation  It is the simplest method for allocating  memory is divided memory into several fixed size partitions. Fixed Equal-size partitions It divides the main memory Into equal number of fixed sized partitions, operating system occupies some fixed portion and remaining portion of main memory is available for user processes. Advantages It supports multi programming. A process whose size is less then or equal to the partitions size can be loaded into any available partition. Disadvantages If a program is big to fit in...
Post a Comment
Read more

What is web browser-computer world

                    What is web browser Web Browser A web browser is a program that your computer runs to communicate with web servers on the internet. Web browser must understand HTML and display text. Web browser are interpreter of HTML language web pages are HTML document send by server on client request and after reaching this document to client side the web browser intro parrots this HTML document in graphical interface.  Web client run Special software called a browser that allow them to  Connect to an appropriate server Query the server for the information to be read.   Provided and interface to read the information returned by the server. web Browser are software installed on your PC. To Excess the you need a web browsers, such as Netscape navigator, Microsoft Internet Explorer or Mozilla Firefox. There are four leading web browser Explorer, Firefox, Netscape and Safari but there are some other browsers a...
Post a Comment
Read more

Memory in computer (primary, secondary and cache memory)-computer world

  Memory : A memory just like a human brain.It is used to store data and instructions. Computer memory is the storage space in the computer, where data is to be processed and instruction  required processing are stored. Computer memory is classified into following types : 1. Cache memory : Cache memory is a very high speed semiconductor memory which can speed up the CPU. It act as buffer(small storage are ) Between the CPU and main memory. We can say that it is a high speed memory between CPU and RAM and it is used temporary store very active data and instruction during processing.  2. Primary memory : Primary holds only that data and instruction on which the computer is currently working. Data holds by primary memory is lost when power is switched of. Primary is not fast as resisters. Primary is divided into two subcategory's : 1. RAM(Random access memory) : Random access memory is a form of computer memory that can be read and change in any any order typically ...
Post a Comment
Read more