C没有开放函数

Question

所以，我的 C 不想打开我的函数。我不知道在哪里进一步查看，因为我不知道我在这方面做错了什么。与其他练习配合使用效果很好。这是我写的:

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>

int hello();
int sum(int);
int k, i, getal1, getal2;
int goobye(void);

int main(void)
{
    int hello();
    for (i = 0; i < 5; i++)
    {
        printf("Give 2 numbers <100 : ");
        scanf("%d%*c%d%*c", &getal1, &getal2);
        int sum(int k);
    }
    int goodbye(void);
}

int hello()
{
    printf("Welcome, this program will ask you to solve 1 sum");
    return 0;
}
int sum(int k)
{
    int som, som2;
    som = getal1 + getal2;
    printf("What is the sum of %d %d? %d", getal1, getal2);
    scanf("%d", &som2);
    if (som == som2)
    {
        printf("According to you, the sum of %d and %d equals %d. That is correct", getal1, getal2, som2);
    }
    else
    {
        printf("According to you, the sum of %d and %d equals %d. That is not correct", getal1, getal2, som2);
    }
    return 0;
}

int goobye(void)
{
    printf("Thanks for your cooperation.");
    return 0;
}

提前致谢!

Answer 1

在主函数中你应该调用一个没有类型的函数

int main(void)
{
hello();
for (i = 0; i < 5; i++)
{
    printf("Give 2 numbers <100 : ");
    scanf("%d%*c%d%*c", &getal1, &getal2);
    sum(k);
}
goodbye();
}

像这样编辑主函数