Sunday, November 25, 2012

CPU scheduling algorithms. -- Short Job First(sjf)

/* Simulate the following cpu scheduling algorithms.
    B. Short Job First(sjf)     */
#include<stdio.h>
#include<conio.h>
void main()
{
    int i,j,bt[10],n,twt=0,temp1,z[20],p[10];
    int wt[10],sum=0,sum1=0;
    float avgt=0.00;
    clrscr();
    printf("\n Enter no. of Processes ::");
    scanf("%d",&n);
    printf("\n Enter the %d burst times::",n);
    for(i=0;i<n;i++)
    {
        printf("\n\n Enter time for process%d::",i+1);
        scanf("%d",&bt[i]);
        p[i]=i+1;
    }
    for(i=0;i<n-1;i++)
    {
        for(j=i+1;j<n;j++)
        {
            if(bt[i]>bt[j])
            {
                temp1=bt[i];
                bt[i]=bt[j];
                bt[j]=temp1;
                temp1=p[i];
                p[i]=p[j];
                p[j]=temp1;
            }
        }
    }
    for(i=0;i<n;i++)
    {
        if(i==0)
        {
            wt[i]=0;
            sum=sum+bt[i];
        }
        else
        {
            wt[i]=sum;
            sum=sum+bt[i];
        }
        sum1=sum1+bt[i];
        z[i]=sum1;
    }
    for(i=0;i<n;i++)
        printf("%d",p[i]);
    printf("\n\n----------------------------------------------\n");
    printf("\n\tPNo\tbt\twt\n");
    printf("\n----------------------------------------------\n");
    for(i=0;i<n;i++)
    {
        twt+=wt[i];
        printf("\n\n\tP%d\t%d\t%d\n",p[i],bt[i],wt[i]);
    }
    printf("\n----------------------------------------------\n");
    avgt=(float)twt/(float)n;
    printf("\n\nGannt Chart ::\n\n");
    printf("\t0");
    for(i=0;i<j-1;i++)
        printf("%4d",z[i]);
    printf("\n\n Total waiting time is ::%d",twt);
    printf("\n\n Average waiting time is ::%f",avgt);
    getch();
}

/* Input and Output :-


 Enter no. of Processes ::3
 Enter the 3 burst times::
 Enter time for process1::24
 Enter time for process2::3
 Enter time for process3::3
  231
----------------------------------------------
    PNo     bt      wt
----------------------------------------------
    P2      3       0
    P3      3       3
    P1      24      6
----------------------------------------------

Gannt Chart ::

    0   3   6

 Total waiting time is ::9
 Average waiting time is ::3.000000        */

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