Guardian C Library Calls Reference Manual

isalnum
3-88 128833—Guardian TNS C Library Calls Reference Manual
Reference to Library Calls
isalnum
The isalnum function tests whether its argument is alphanumeric.
character
specifies the character to test.
Return Value
is nonzero if character is an uppercase or lowercase character or a digit; otherwise,
isalnum returns the value zero.
Usage Guidelines
•
The character-testing routine isalnum is implemented as a macro, but the C compiler
provides an underlying function with the same name as the macro. Although the
macro is faster than the function, it evaluates its argument more than once.
Consequently, if you need to provide an expression with side effects as the argument
to this routine, you should undefine the macro so that the C compiler uses the
function instead. For more information about undefining macros, refer to the C/C++
Programmer’s Guide.
#include <ctypeh>
int isalnum(int character);