sp-lab/9.c

#include <stdio.h>

#define MAX 50

int stack[MAX], top = -1;

// check if page is in stack
int inStack(int page, int frames) {
    for (int i = top; i > top - frames && i >= 0; i--)
        if (stack[i] == page) return i;
    return -1;
}

int main() {
    int pages[MAX], n, frames;

    printf("Enter number of pages: ");
    scanf("%d", &n);
    printf("Enter reference string: ");
    for (int i = 0; i < n; i++)
        scanf("%d", &pages[i]);
    printf("Enter number of frames: ");
    scanf("%d", &frames);

    int faults = 0;

    printf("\nPage\tFrames\t\t\tFault\n");

    for (int i = 0; i < n; i++) {
        int pos = inStack(pages[i], frames);

        printf("%d\t", pages[i]);

        if (pos == -1) {
            // page not found — fault
            stack[++top] = pages[i];
            faults++;

            // print current frames (top 'frames' elements)
            int start = top - frames + 1;
            if (start < 0) start = 0;
            for (int j = start; j <= top; j++)
                printf("%d ", stack[j]);
            printf("\t\tFault");
        } else {
            // page found — move it to top (most recently used)
            for (int j = pos; j < top; j++)
                stack[j] = stack[j + 1];
            stack[top] = pages[i];

            // print current frames
            int start = top - frames + 1;
            if (start < 0) start = 0;
            for (int j = start; j <= top; j++)
                printf("%d ", stack[j]);
        }

        printf("\n");
    }

    printf("\nTotal Page Faults: %d\n", faults);
    return 0;
}