Shortest Job First (SJF) scheduling



Shortest Job First (SJF) scheduling

In this algorithm there are three algorithms those are:

·         SJF  is a non-preemptive algorithm
·         Shortest Remaining Time First (SRTF)
·         Longest Remaining Time First (LRTF)

SJF is a non-preemptive algorithm

Shortest job first (SJF), is a scheduling policy that selects the waiting process with the smallest execution time to execute next. SJN is a non-preemptive algorithm.

1.      Shortest Job first has the advantage of having minimum average waiting time among all scheduling algorithms.
2.      It is a Greedy Algorithm.
3.      It may cause starvation if shorter processes keep coming. This problem can be solved using the concept of aging.
4.      It is practically infeasible as Operating System may not know burst time and therefore May not sort them. While it is not possible to predict execution time, several methods can be used to estimate the execution time for a job, such as a weighted average of previous execution times. SJF can be used in specialized environments where accurate estimates of running time are available.

Comments

Post a Comment

Popular posts from this blog

Write C programs to simulate the Paging techniques of memory management

Image
#include<stdio.h> #define MAX 50 int main() { int page[MAX],i,n,f,ps,off,pno; int choice=0; printf("\nEnter the no of  peges in memory: "); scanf("%d",&n); printf("\nEnter page size: "); scanf("%d",&ps); printf("\nEnter no of frames: "); scanf("%d",&f); for(i=0;i<n;i++) page[i]=-1; printf("\nEnter the page table\n"); printf("(Enter frame no as -1 if that page is not present in any frame)\n\n"); printf("\npageno\tframeno\n-------\t-------"); for(i=0;i<n;i++) { printf("\n\n%d\t\t",i); scanf("%d",&page[i]); } do { printf("\n\nEnter the logical address(i.e,page no & offset):"); scanf("%d%d",&pno,&off); if(page[pno]==-1) printf("\n\nThe required page is not available in any of frames"); else printf("\n\nPhysical address(i.e,frame no & offset):%d,%d",page[pno],off); prin
Read more

Write C programs to simulate the Two level directory File organization technique

Write C programs to simulate the Two level directory File organization technique #include<string.h> #include<stdlib.h> #include<stdio.h> struct { char dname[10],fname[10][10]; int fcnt; }dir[10]; void main() { int i,ch,dcnt,k; char f[30], d[30]; dcnt=0; while(1) { printf("\n\n1. Create Directory\t2. Create File\t3. Delete File"); printf("\n4. Search File\t\t5. Display\t6. Exit\tEnter your choice -- "); scanf("%d",&ch); switch(ch) { case 1: printf("\nEnter name of directory -- "); scanf("%s", dir[dcnt].dname); dir[dcnt].fcnt=0; dcnt++; printf("Directory created"); break; case 2: printf("\nEnter name of the directory -- "); scanf("%s",d); for(i=0;i<dcnt;i++) if(strcmp(d,dir[i].dname)==0) { printf("Enter name of the file -- "); scanf("%s",dir[i].fname[dir[i].fcnt]); printf("File created"); break; } if(i==dcnt) printf
Read more

Write C programs to simulate the Hierarchical directory File organization technique

Write C programs to simulate the Hierarchical  directory File organization technique #include<stdio.h> #include<graphics.h> #include<string.h> struct tree_element { char name[20]; int x, y, ftype, lx, rx, nc, level; struct tree_element *link[5]; }; typedef struct tree_element node; void main() { int gd=DETECT,gm; node *root; root=NULL; create(&root,0,"root",0,639,320); clrscr(); initgraph(&gd,&gm,"c:\tc\BGI"); display(root); closegraph(); } create(node **root,int lev,char *dname,int lx,int rx,int x) { int i, gap; if(*root==NULL) { (*root)=(node *)malloc(sizeof(node)); printf("Enter name of dir/file(under %s) : ",dname); fflush(stdin); gets((*root)->name); printf("enter 1 for Dir/2 for file :"); scanf("%d",&(*root)->ftype); (*root)->level=lev; (*root)->y=50+lev*50; (*root)->x=x; (*root)->lx=lx; (*root)->rx=rx; for(i=0;i<5;i++) (*root)->li
Read more