Format
#include <math.h> double erf(double x); double erfc(double x);
Language Level: XPG4
erf calculates the error function of

erfc computes the value of 1.0 - erf(x). erfc is used in place of erf for large values of x.
Return Value
erf returns a double value that represents the error
function. erfc returns a double value representing 1.0 - erf.
Example
This example uses erf and erfc to compute the error
function of two numbers.
#include <stdio.h> #include <math.h>
double smallx, largex, value;
int main(void)
{
smallx = 0.1;
largex = 10.0;
value = erf(smallx); /* value = 0.112463 */
printf("Error value for 0.1: %lf\n", value);
value = erfc(largex); /* value = 2.088488e-45 */
printf("Error value for 10.0: %le\n", value);
return 0;
/*******************************************************
The output should be:
Error value for 0.1: 0.112463
Error value for 10.0:2.088488e-45
*******************************************************/
}
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<math.h>