isxdigit

From cppreference.com
< c‎ | string‎ | byte
Defined in header <ctype.h>
int isxdigit( int ch );

Checks if the given character is a hexadecimal numeric character (0123456789abcdefABCDEF) or is classified as a hexadecimal character.

The behavior is undefined if the value of ch is not representable as unsigned char and is not equal to EOF.

Parameters

ch - character to classify

Return value

Non-zero value if the character is an hexadecimal numeric character, zero otherwise.

Notes

isdigit and isxdigit are the only standard narrow character classification functions that are not affected by the currently installed C locale. although some implementations (e.g. Microsoft in 1252 codepage) may classify additional single-byte characters as digits.