The **`erff` function** is defined in the `<math.h>` header file in C. It takes in a single parameter: a `float` value. It then computes the error function of the given argument and returns a value of type `float`. 

The #key# error function: also known as Gauss error function  #key# in mathematics is defined as follows:

> erf $z$ = $\frac{2}{\sqrt{\pi}}$ $\int_{0}^{arg} e^{-t^2} dt$ 

> The argument to the `erff` function serves as the upper limit in the integral above.

The error function is widely used in probability and statistics. It integrates the normal distribution and gives the probability that a normally distributed random variable Y (with mean 0 and variance ½) falls into the range [−x, x].

The illustration below shows how `erff` function works: 

# Declaration

The `erff` function is defined as follows:

```C
float erff(float arg);
```
It takes in a single value of type `float` and computes its error function. It then returns the answer of type `float`.


# Error handling

The `erff` function returns special values for certain arguments:

* If the argument is +-0, +-0 is returned
* If the argument is +-$\infty$, +- $\infty$ is returned
* If the argument is `NAN`, `NAN` is returned

# Examples

The following code snippet shows how we can use the `erff` function:

#include <stdio.h> // Including header file for printf function
#include <math.h>  // Including header file for erf function

int main (){

  float param, result;
  param = 4.0;
  result = erff(param);
  printf("erff (%f) = %f\n", param, result);
  return 0;
}

The following code snippet shows how error handling in `erff` function works:

#include <stdio.h> // Including header file for printf function
#include <math.h>  // Including header file for erf function

int main (){

  printf("erff (%f) = %f\n", 0.0, erff(0.0));
  return 0;
}

What is erff in C?

Computes the Gauss error function for a float argument, used in probability and statistics.