#include <stdio.h>
#include <stdbool.h>

#define N 8

typedef struct {
    bool present;
    unsigned loc;
} PTE;

static void dump(const PTE pt[]) {
    puts("VPN Present Location");
    for (int i = 0; i < N; i++)
        printf("%3d %7s %8u\n", i, pt[i].present ? "yes" : "no", pt[i].loc);
}

int main(void) {
    PTE pt[N] = {
        {true, 0}, {true, 1}, {false, 4}, {true, 2},
        {false, 6}, {false, 2}, {true, 3}, {false, 7}
    };
    puts("=== Tiny VM with Swap Simulator ===");
    puts("Initial page table:");
    dump(pt);
    puts("\nCPU references VPN 2 -> present bit clear -> PAGE FAULT");
    puts("Handler reads disk block 4, evicts VPN 0 to swap 0, places page in PFN 0");
    pt[0].present = false;
    pt[0].loc = 0;
    pt[2].present = true;
    pt[2].loc = 0;
    puts("Page table after fault handling:");
    dump(pt);
    puts("\nCPU references VPN 6 -> present, PFN 3, no fault");
    puts("Large virtual memory illusion maintained.");
    return 0;
}