# C library - fabs() function

The C math library fabs() function accepts the parameter(x) of type double that returns the absolute value of x. This function is defined under the header <math.h> that calculates the absolute value of a float point number.

## Syntax

Following is the syntax of the C library fabs() function −

```double fabs(double x)
```

## Parameters

This function accepts only a single parameter −

• x − This is the floating point value.

## Return Value

This function returns the absolute value of x.

## Example

Following is the C library program to see the illustration of fabs() function.

```#include <stdio.h>
#include <math.h>

int main () {
int a, b;
a = 1234;
b = -344;

printf("The absolute value of %d is %lf\n", a, fabs(a));
printf("The absolute value of %d is %lf\n", b, fabs(b));

return(0);
}
```

### Output

The above code produces the following result −

```The absolute value of 1234 is 1234.000000
The absolute value of -344 is 344.000000
```

## Example

Below the program calculate absolute value of floating-point numbers. Here, we have two types of absolute value − positive and negative, and when these value are passes to the function fabs(), it display the result.

```#include <stdio.h>
#include <math.h>

int main() {
double a = 9801.0;
double b = -1831.0;
double res;

res = fabs(a);
printf("The absolute value of %.3lf is %.3lf\n", a, res);

res = fabs(b);
printf("The absolute value of %.3lf is %.3lf\n", b, res);

return 0;
}
```

### Output

On execution of above code, we get the following result −

```The absolute value of 980.000 is 980.000
The absolute value of -1231.000 is 1231.000
```

## Example

Here, we calculate the approximate absolute value of long double numbers. The result of approximate number can be identify using the formula tanh = (1.0 + tanh(x / 2.0)) * (1.0 - tanh(x / 2.0).

```#include <stdio.h>
#include <math.h>

long double my_exp(long double x) {
return (1.0 + tanh(x / 2.0)) * (1.0 - tanh(x / 2.0));
}

int main() {
long double a = -6.546;
long double b = 5.980;
double res;

res = fabs(a);
printf("The absolute value of %.3Lf is %.3lf\n", a, res);

res = fabs(b);
printf("The absolute value of %.3Lf is %.3lf\n", b, res);

return 0;
}
```

### Output

After executing the above code, we get the following result −

```The absolute value of -6.546 is 6.546
The absolute value of 5.980 is 5.980
```