C语言多文件编程

#include <stdio.h>
int fun1(){
printf("The first function!\n");
return 0;
}
int fun2(){
printf("The second function!\n");
return 0;
}
int fun3(){
printf("The third function!\n");
return 0;
}

#ifndef _FUN_H
#define _FUN_H

extern int fun1(void);
extern int fun2(void);
extern int fun3(void);

#endif

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

int main(){
fun1();
fun2();
fun3();

system("pause");
return 0;
}