#include <stdio.h> 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; }