isalnum : alphanumeric character predicate
Synopsis
Section titled “Synopsis”#include <ctype.h>int isalnum(int c);```### Description
isalnum is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for alphabetic or numeric ASCII characters, and 0 for other arguments. It is defined for all integer values.
You can use a compiled subroutine instead of the macro definition by undefining the macro using `#undef isalnum'.### Returns
isalnum returns non-zero if c is a letter (a--z or A--Z) or a digit (0--9).
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**Authoritative source**: BUSMASTER DITA help source `isalnum.dita`, compiled into `BUSMASTER.CHM` with the application.