C语言实例33:内部和外部函数

//extern.c

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

int main(int argc, char *argv[])
{
    extern int multiply();
    extern int sum();
    int a, b;
    int result;
    printf("Please input a and b: ");
    scanf("%d, %d", &a, &b);
    result = multiply(a, b);
    printf("The result of multiply is: %d",result);
    result = sum(a, b);
    printf("\nThe result of sum is: %d\n", result);

    system("pause");
    return 0;
}

//file.c

#include <stdio.h>

extern int multiply(int a, int b)
{
    int c;
    c = a * b;
    return c;


}

//file2.c

#include <stdio.h>

extern int sum(int a, int b)
{
    int c;
    c = a + b;
    return c;
}