#include <stdio.h>
#include <stdlib.h>

int main() {
    FILE *fp;
    int numbers[10];
    int i, value;

    // Initialize and write numbers 1 to 10
    for (i = 0; i < 10; i++) {
        numbers[i] = i + 1;
    }

    fp = fopen("data.bin", "wb");
    if (fp == NULL) {
        perror("Error opening file for writing");
        return 1;
    }

    fwrite(numbers, sizeof(int), 10, fp);
    fclose(fp);
    printf("Wrote numbers 1 to 10 to file.\n");

    // Reopen file for reading and writing
    fp = fopen("data.bin", "rb+");
    if (fp == NULL) {
        perror("Error opening file for reading and writing");
        return 1;
    }

    // Move file pointer to the 5th integer (index 4)
    fseek(fp, 4 * sizeof(int), SEEK_SET);

    // Read that integer
    fread(&value, sizeof(int), 1, fp);
    printf("Value at position 5 before modification: %d\n", value);

    // Move pointer back to the same position
    fseek(fp, 4 * sizeof(int), SEEK_SET);

    // Modify the 5th integer to 999
    value = 999;
    fwrite(&value, sizeof(int), 1, fp);
    printf("Modified value at position 5 to 999.\n");

    fclose(fp);

    // Verify modification
    fp = fopen("data.bin", "rb");
    if (fp == NULL) {
        perror("Error opening file for verification");
        return 1;
    }

    printf("\nFile contents after modification:\n");
    for (i = 0; i < 10; i++) {
        fread(&value, sizeof(int), 1, fp);
        printf("%d ", value);
    }
    printf("\n");

    fclose(fp);
    return 0;
}