isalnum Function (Macro)

ctype.h

short isalnum (short c);

Checks whether a character is an alphanumeric.

isalnum returns nonzero if c is a letter ('A' to 'Z' or 'a' to 'z') or a digit ('0' to '9'), otherwise it returns zero. It is an inline function which is implemented using GNU C smart macros, which expands to a medium-sized code.