isupper

int isupper( int ch );

Checks if the given character is an uppercase character according to the current C locale. In the default "C" locale, isupper returns true only for the uppercase letters (ABCDEFGHIJKLMNOPQRSTUVWXYZ).

If isupper returns true, it is guaranteed that iscntrl, isdigit, ispunct, and isspace return false for the same character in the same C locale.

The behavior is undefined if the value of ch is not representable as unsigned char and is not equal to EOF.

Parameters

Return value

Non-zero value if the character is an uppercase letter, zero otherwise.

Example

#include <stdio.h>
#include <ctype.h>
#include <locale.h>
 
int main(void)
{
    unsigned char c = '\xc6'; // letter Æ in ISO-8859-1
    printf("In the default C locale, \\xc6 is %suppercase\n",
           isupper(c) ? "" : "not " );
    setlocale(LC_ALL, "en_GB.iso88591");
    printf("In ISO-8859-1 locale, \\xc6 is %suppercase\n",
           isupper(c) ? "" : "not " );
}

In the default C locale, \xc6 is not uppercase
In ISO-8859-1 locale, \xc6 is uppercase

References

• C11 standard (ISO/IEC 9899:2011):
• 7.4.1.11 The isupper function (p: 203)
• C99 standard (ISO/IEC 9899:1999):
• 7.4.1.11 The isupper function (p: 184)
• C89/C90 standard (ISO/IEC 9899:1990):
• 4.3.1.10 The isupper function

See also