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Write the simulation program to implement demand paging and show the page scheduling and total number of page faults for the following given page reference string. Give input n as the number of memory frames. Reference String : 12,15,12,18,6,8,11,12,19,12,6,8,12,15,19,8 Implement LRU


 #include<stdio.h>

#define MAX 20
int frames[MAX],ref[MAX],mem[MAX][MAX],faults,sp,m,n,time[MAX];

void accept()
{
    int i;
    printf("Enter Number of frames : ");
    scanf("%d",&n);
   
    printf("Enter Number of references : ");
    scanf("%d",&m);
   
    printf("Enter references string : ");
    for (i=0;i<m;i++)
    {
        printf("[%d] : ",i);
        scanf("%d",&ref[i]);
    }
}

void disp()
{
    int i,j;
    for (i=0;i<m;i++)
        printf("%3d",ref[i]);
    printf("\n\n");
    for (i=0;i<n;i++)
    {
        for (j=0;j<m;j++)
        {
            if (mem[i][j])
                printf("%3d",mem[i][j]);
            else
                printf(" ");
        }
        printf("\n");
    }
    printf("Total Page Faults : %d \n",faults);
}

int search(int pno)
{
    int i;
    for (i=0;i<n;i++)
    {
        if(frames[i]==pno)
            return i;
    }
    return -1;
}

int get_lru()
{
    int i,min_i,min=9999;
    for (i=0;i<n;i++)
    {
        if (time[i]<min)
        {
            min=time[i];
            min_i=i;
        }
    }
    return min_i;
}

void lru()
{
    int i,j,k;
    for (i=0;i<m && sp<n;i++)
    {
        k=search(ref[i]);
        if(k==-1)
        {
            frames[sp]=ref[i];
            time[sp]=i;
            faults++;
            sp++;
            for (j=0;j<n;j++)
                mem[j][i]=frames[j];
        }
        else
            time[k]=i;
    }
    for (;i<m;i++)
    {
        k=search(ref[i]);
        if (k==-1)
        {
            sp=get_lru();
            frames[sp]=ref[i];
            time[sp]=i;
            faults++;
            for(j=0;j<n;j++)
                mem[j][i]=frames[j];
        }
        else
            time[k]=i;
    }
}

int main()
{
    accept();
    lru();
    disp();
    return 0;
}

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