译文： https://beginnersbook.com/2015/02/c-program-to-check-whether-the-given-integer-is-positive-or-negative/

    在下面的程序中，我们检查输入整数是正数还是负数。如果输入数字大于零，则其为正数，否则为负数。如果数字为零则既不是正数也不是负数。我们在下面的 C 程序中遵循了相同的逻辑。

    1. /* Description: A program to check whether the input
    2.  * integer number is positive or negative. 
    3.  * Written by: Chaitanya Singh
    4.  * Published on: beginnersbook.com
    5.  */
    6. #include <stdio.h>
    8. void main()
    9. {
    10.     int num;
    12.     printf("Enter a number: \n");
    13.     scanf("%d", &num);
    14.     if (num > 0)
    15.         printf("%d is a positive number \n", num);
    16.     else if (num < 0)
    17.         printf("%d is a negative number \n", num);
    18.     else
    19.         printf("0 is neither positive nor negative");
    20. }

    输出 1：

    1. Enter a number:
    2. 0
    3. 0 is neither positive nor negative

    输出 2：

    1. Enter a number:
    2. -3
    3. -3 is a negative number

    输出 3：

    1. Enter a number:
    2. 100
    3. 100 is a positive number