c语言函数如何声明

#include <stdio.h>

//函数声明

int sum(int m, int n);  //也可以写作int sum(int, int);

int main(){

    int begin = 5, end = 86;

    int result = sum(begin, end);

    printf("The sum from %d to %d is %d\n", begin, end, result);

    return 0;

}

//函数定义

int sum(int m, int n){

    int i, sum=0;

    for(i=m; i<=n; i++){

        sum+=i;

    }

    return sum;

}