Defined in header <locale>
template< class charT >
bool isupper( charT ch, const locale& loc );

Checks if the given character is classified as an uppercase alphabetic character by the given locale's std::ctype facet.


ch - character
loc - locale

Return value

Returns true if the character is classified as uppercase, false otherwise.

Possible implementation

template< class charT >
bool isupper( charT ch, const std::locale& loc ) {
    return std::use_facet<std::ctype<charT>>(loc).is(std::ctype_base::upper, ch);


Demonstrates the use of isupper() with different locales (OS-specific).

#include <iostream>
#include <locale>
int main()
    const wchar_t c = L'\u00de'; // capital letter thorn
    std::locale loc1("C");
    std::cout << "isupper('Þ', C locale) returned "
               << std::boolalpha << std::isupper(c, loc1) << '\n';
    std::locale loc2("en_US.UTF8");
    std::cout << "isupper('Þ', Unicode locale) returned "
              << std::boolalpha << std::isupper(c, loc2) << '\n';


isupper('Þ', C locale) returned false
isupper('Þ', Unicode locale) returned true

See also

checks if a character is an uppercase character
checks if a wide character is an uppercase character

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