C Program to Find Absolute Value With/ Without Using Built-in Functions

C Program to Find the Absolute Value of a Number

In this post, we’ll learn how to find the absolute value of a given number using a simple C program. The absolute value of a number is its distance from zero, regardless of sign.

C Program Code

#include <stdio.h>
#include <stdlib.h> // For the abs() function for integers and fabs() for floating point

int main() {
    double number, absolute_value;

    // Prompt the user to enter a number
    printf("Enter a number: ");
    scanf("%lf", &number);

    // Find the absolute value
    absolute_value = fabs(number);

    // Display the absolute value
    printf("The absolute value of %.2lf is %.2lf\n", number, absolute_value);

    return 0;
}

How the Program Works

  • We include the standard I/O library <stdio.h> and <stdlib.h> for the fabs() function.
  • We declare two double variables: number and absolute_value.
  • We prompt the user to enter a number and read the input using scanf().
  • We calculate the absolute value using the fabs() function.
  • We display the result with two decimal precision using printf().

Example Output

Here’s an example of what the output might look like: 

Enter a number: -8.5
The absolute value of -8.50 is 8.50

Conclusion

This simple C program demonstrates how to find the absolute value of a number using the fabs() function. You can easily adapt it for integers by using the abs() function instead.

C Program to Find Absolute Value Without Built-in Functions

This program calculates the absolute value of a number manually, without using any built-in functions like fabs() or abs(). The absolute value is simply the number itself if it's positive or zero, and its negation if it's negative.

C Program Code

#include <stdio.h>

int main() {
    double number, absolute_value;

    // Prompt the user to enter a number
    printf("Enter a number: ");
    scanf("%lf", &number);

    // Calculate absolute value manually
    if (number < 0) {
        absolute_value = -number;
    } else {
        absolute_value = number;
    }

    // Display the absolute value
    printf("The absolute value of %.2lf is %.2lf\n", number, absolute_value);

    return 0;
}

How the Program Works

  • We prompt the user to enter a number.
  • If the number is negative, we multiply it by -1 to make it positive.
  • If the number is zero or positive, we leave it as is.
  • Finally, we display the absolute value.

Example Output

Here’s what the output looks like: 

Enter a number: -12.34
The absolute value of -12.34 is 12.34

Conclusion

This example demonstrates how to compute the absolute value manually without relying on built-in functions, which can be useful for learning or in environments where standard libraries are limited.

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