lab18.c

ALL LINUX LAB PROGRAM MIT MANIPAL 2008-09 BATCH

#include<stdio.h>
void print_mem(int mem[],int m)


    {
    int i;
    for(i=0;i<m;i++)
    printf("\t%d",mem[i]);
    printf("\n");
}

int optimal1(int p,int ref[],int n,int c)


    {
    int i;
    for(i=c+1;i<n;i++)


        {
        if(ref[i]==p)
        return i;
    }

    return -99;
}

int optimal2(int index[],int m)


    {
    int i,max=-99;
    for(i=0;i<m;i++)
    if(max<index[i])
    max=index[i];
    return max;
}

int main()


    {
    int ref[25],mem[10],index[10],i,j,k,flag,n,m,p,pf,ch,fifo_pf,o_pf;
    printf("\t\tPAGE REPLACEMENT STRATEGIES - FIFO & Optimal \n\n");
    printf("Enter the number of pages in the reference string:");
    scanf("%d",&n);
    printf("\nEnter the reference string:\n");
    for(i=0;i<n;i++)


        {
        printf("Enter the page reference - %d: ",i+1);
        scanf("%d",&ref[i]);
    }

    printf("Enter the number of frames:");
    scanf("%d",&m);
    //FIFO Algorithm
    printf("\n\n\tFIFO Algorithm\n\n");
    j=0;
    pf=0;
    for(i=0;i<m;i++)
    mem[i]=-1;
    for(i=0;i<n;i++)


        {
        p=ref[i];
        flag=0;
        for(k=0;k<m;k++)
        if(mem[k]==p)
        flag=1;
        if(flag!=1)


            {
            mem[j]=p;
            j=(j+1)%m;
            pf++;
        }

        printf("%d --",p);
        print_mem(mem,m);
    }

    printf("\nNumber of page faults = %d\n",pf);
    fifo_pf=pf;
    //Optimal Algorithm
    printf("\n\n\tOPTIMAL Algorithm\n\n");
    j=0;
    pf=0;
    for(i=0;i<m;i++)
    mem[i]=-1;
    for(i=0;i<n;i++)


        {
        p=ref[i];
        flag=0;
        for(k=0;k<m;k++)
        if(mem[k]==p)


            {
            flag=1;
            break;
        }

        else if(mem[k]==-1)


            {
            mem[k]=p;
            pf++;
            flag=1;
            break;
        }

        if(flag==0)


            {
            pf++;
            for(k=0;k<m;k++)
            index[k]=optimal1(mem[k],ref,n,i);
            for(k=0;k<m;k++)
            if(index[k]==-99)


                {
                mem[k]=p;
                flag=1;
                break;
            }

            if(flag==0)


                {
                j=optimal2(index,m);
                for(k=0;k<m;k++)
                if(mem[k]==ref[j])
                mem[k]=p;
            }

        }

        printf("%d --",p);
        print_mem(mem,m);
    }

    printf("\nMumber of page faults = %d\n",pf);
    o_pf=pf;
    if(o_pf==fifo_pf)
    printf("\nBoth the replacement strategies are efficient.");
    else if(o_pf<fifo_pf)
    printf("\nOptimal Page Replacement Strategy is efficient.");
    else
    printf("\nFIFO Page Replacement Strategy is efficient.");
}