Identification of ASCII letter

[Classification]

Standard library

[Syntax]

#include <ctype.h>

int isalpha(int c);

[Return value]

These macros return a value other than 0 if the value of argument c matches the respective description (i.e., if the result is true). If the result is false, 0 is returned.

[Description]

This function is a macro that checks whether a given character is an ASCII alphabetic character. This macro is defined only when c is made true by isascii or when c is EOF. A compiled subroutine can be used instead of the macro definition, which is invalidated by using "#undef isalpha".