int main(void)
{
    char temp1[100];
    char temp2[100];
    FILE *p_jack;
    FILE *p_retchie;

    p_jack = fopen("e:/jack.txt", "r");
    p_retchie = fopen("e:/retchie.txt", "r");

    if (p_jack != NULL  && p_retchie != NULL)
    {
        fgets(temp1, 20, p_jack);
        fgets(temp2, 20, p_retchie);
    }
    fclose(p_jack);
    fclose(p_retchie);

    p_jack = fopen("e:/jack.txt", "w");
    p_retchie = fopen("e:/retchie.txt", "w");

    if (p_jack != NULL  && p_retchie != NULL)
    {
        fprintf(p_jack, "%s", temp2);
        fprintf(p_retchie, "%s", temp1);

        fclose(p_jack);
        fclose(p_retchie);
    }
    return 0;
}