C Program to Check Whether a Number is Positive or Negative

You will learn to check whether a number (entered by the user) is negative or positive in this example.

To understand this example, you should have the knowledge of following C programming topics:

Positive and negative numbers in a number line

This program takes a number from the user and checks whether that number is either positive or negative or zero.

Example #1: Check if a Number is Positive or Negative Using if...else

#include <stdio.h>
int main()
{
    double number;

    printf("Enter a number: ");
    scanf("%lf", &number);

    if (number <= 0.0)
    {
        if (number == 0.0)
            printf("You entered 0.");
        else
            printf("You entered a negative number.");
    }
    else
        printf("You entered a positive number.");
    return 0;
}

You can also solve this problem using nested if else statement.

Example #2: Check if a Number is Positive or Negative Using Nested if...else

#include <stdio.h>
int main()
{
    double number;

    printf("Enter a number: ");
    scanf("%lf", &number);

    // true if number is less than 0
    if (number < 0.0)
        printf("You entered a negative number.");

    // true if number is greater than 0
    else if ( number > 0.0)
        printf("You entered a positive number.");

    // if both test expression is evaluated to false
    else
        printf("You entered 0.");
    return 0;
}

Output 1

Enter a number: 12.3
You entered a positive number.

Output 2

Enter a number: 0
You entered 0.