c语言中的简单加法

#include <stdio.h>//方便打印出来
int main()
{
  int a = 12;
  int b = 23;
  int sum = a + b;
  printf("sum=%d\n",sum);

  return 0;
}

#include <stdio.h>
int p = 10;
int ADD(int x,int y)//定义新的函数
{
  int z = x + y;
  return z;
}
int main()
{

  int i = 40;
  int q = 50;
  int sum = ADD(i,q);
  printf("sum=%d\n",sum);

  return 0;
}

有错误请指教，谢谢