std::isupper

Header: <cctype>

Checks if the given character is an uppercase character as classified by the currently installed C locale. In the default “C” locale, std::isupper returns a nonzero value only for the uppercase letters (ABCDEFGHIJKLMNOPQRSTUVWXYZ).

# Declarations

int isupper( int ch );

# Parameters

ch: character to classify

# Return value

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

# Notes

Like all other functions from , the behavior of std::isupper is undefined if the argument’s value is neither representable as unsigned char nor equal to EOF. To use these functions safely with plain chars (or signed chars), the argument should first be converted to unsigned char:

Similarly, they should not be directly used with standard algorithms when the iterator’s value type is char or signed char. Instead, convert the value to unsigned char first:

# Example

#include <cctype>
#include <clocale>
#include <iostream>
 
int main()
{
    unsigned char c = '\xc6'; // letter Æ in ISO-8859-1
 
    std::cout << "isupper(\'\\xc6\', default C locale) returned "
              << std::boolalpha << (bool)std::isupper(c) << '\n';
 
    std::setlocale(LC_ALL, "en_GB.iso88591");
    std::cout << "isupper(\'\\xc6\', ISO-8859-1 locale) returned "
              << std::boolalpha << (bool)std::isupper(c) << '\n';
 
}