isupper()

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 isupper() function tests for any uppercase letter A through Z.

Returns:

Nonzero if c is an uppercase letter; otherwise, zero.

Examples:

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

char the_chars[] = { 'A', 'a', 'z', 'Z' };

#define SIZE sizeof( the_chars ) / sizeof( char )

int main( void )
{
    int i;

    for( i = 0; i < SIZE; i++ ) {
        if( isupper( (unsigned)the_chars[i] ) ) {
            printf( "Char %c is an uppercase character\n",
                the_chars[i] );
        } else {
            printf( "Char %c is not an uppercase character\n",
                the_chars[i] );
        }
    }
    
    return EXIT_SUCCESS;
}

produces the output:

Char A is an uppercase character
Char a is not an uppercase character
Char z is not an uppercase character
Char Z is an uppercase character

Classification:

ANSI, POSIX 1003.1