关系表达式和逻辑表达式

算术运算符的优先级高于关系运算符、关系运算符的优先级高于逻辑与和逻辑或运算符

if判断

#include <stdio.h>
int main()
{
  int a;
  while (scanf("%d", &a) != EOF)
  {
    printf("a=%d\n", a);
    if (a > 0)
    {
      printf("a is bigger than 0 \n");
    }
    else if (a > 5)
    {
      printf("a is bigger than 5 \n");
    }
    else
    {
      printf("no no no\n");
    }
  }
  return 0;
}