erf() returns the value of the error function. The definition of the erf() function is (2/sqrt(pi)) times the area under the curve exp(-t * t) between 0 and x. erfc() returns (1.0-erf(x)). Entry-Point Names Generic Compaq Function Data Type OpenVMS Tru64 UNIX Name Required Alpha Alpha erf S_FLOAT math$erf_s erff T_FLOAT math$erf_t erf X_FLOAT math$erf_x erfl F_FLOAT math$erf_f G_FLOAT math$erf_g erfc S_FLOAT math$erfc_s erfcf T_FLOAT math$erfc_t erfc X_FLOAT math$erfc_x erfcl F_FLOAT math$erfc_f G_FLOAT math$erfc_g