In this blog post, you will learn how to write a C program to check the given number positive or negative? This question helps you to increase your logical skill. You will get the answer to the following questions;

• How do you find a given number is positive or negative?
• How do you check if a number is a positive integer in C?
• Write the C program to take input any number from the user and check whether the given number is positive or negative using the bitwise Operators and ternary operators.

How to determine a number is positive or negative?

Using the relational operators (< or >) you can check a number is positive or negative. A number that is greater than zero is termed a positive number whereas the number less than zero is the negative number Let see an example,

• A number ‘n’ is said negative if it is less than 0 i.e. n< 0.
• A number ‘n’ is said positive if it is greater than 0 i.e. n> 0.

But using the MSB (most significant bit) you can also check number is positive or not.

• A number ‘n’ is said negative if MSB  of an integer is 1.
• A number ‘n’ is said positive if MSB  of an integer is 0.

C program to check given number positive or negative:

Method 1: Using the if-else and relational operator

You can check whether a number is positive or negative with the help of a relational operator. See the below code.

#include <stdio.h>

int main()
{
    int sign = 0;
    int data = 0;

    printf("\n\n Enter the number  = ");
    scanf("%d",&data); //Get the number

    sign = (data > 0) - (data < 0); // check the sign of the number
    if(sign == 1)
    {
        printf("\n\n Enter number is a positve number\n");
    }
    else if(sign == -1)
    {
        printf("\n\n Enter number is a negative number\n");
    }
    else
    {
        printf("\n\n Enter number is zero\n");
    }

    return 0;
}

Output:

Method 2: C program to find Positive or Negative Number using MSB:

In the below code, we are checking the MSB bit of a given number. If MSB bit 1, then the number is negative otherwise positive.

#include <stdio.h>

// Total bits required to represent integer
#define BITS sizeof(int) * 8

int main()
{
    int num;

    printf("Enter any number: ");
    scanf("%d", &num);

    (num & (1 << (BITS - 1)))? printf("Negative number\n"):printf("Positive number\n");

    return 0;
}

Output:

Enter any number: -10
Negative number

Method-3: C program to find Positive or Negative number using Conditional Operator

This program asks the user to enter any number. Next, this C program checks whether the given value is positive or negative or zero using Conditional Operator or Ternary operator.

#include <stdio.h>

int main()
{
    int sign = 0;
    int data = 0;

    printf("\n\n Enter the number  = ");
    scanf("%d",&data); //Get the number

    // check the sign of the number
    sign = (data > 0) - (data < 0);

    (sign > 0)? printf(" Number is Positive \n"):printf(" Number is Negative \n");

    return 0;
}

Output:

Enter any number: 10
Positive number

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