isalpha()

Arguments:

c

The character you want to test. This must be representable as an unsigned char or be EOF; the behavior for other values is undefined. Because this argument is interpreted as an int, to avoid sign extension on character values greater than 0x7F, you must cast the argument to the unsigned data type; otherwise, the function will behave unpredictably.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The isalpha() function tests if the argument c is an alphabetic character (a to z and A to Z). An alphabetic character is any character for which isupper() or islower() is true.

Returns:

Nonzero if c is an alphabetic character; otherwise, zero.

Examples:

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

int main( void )
{
    if( isalpha( (unsigned)getchar() ) ) {
      printf( "That's alphabetic\n" );
    }
    
    return EXIT_SUCCESS;
}

Classification:

ANSI, POSIX 1003.1