# if defined(_WIN32_WINNT_VISTA) && WINVER >= _WIN32_WINNT_VISTA && defined(LOCALE_NAME_USER_DEFAULT)
    GetLocaleInfoEx(LOCALE_NAME_USER_DEFAULT, LOCALE_IFIRSTDAYOFWEEK, wsDay, 4)
# else
    GetLocaleInfo(LOCALE_USER_DEFAULT, LOCALE_IFIRSTDAYOFWEEK, wsDay, 4)
# endif

#include <stdio.h>
#include <windows.h>

int main(
    )
{
    int       ret;
    int       first_weekday;
    DWORD     week_1stday;

    ret = GetLocaleInfoEx(LOCALE_NAME_USER_DEFAULT,
                          LOCALE_IFIRSTDAYOFWEEK | LOCALE_RETURN_NUMBER,
                          (LPWSTR) & week_1stday,
                          sizeof(week_1stday) / sizeof(WCHAR));
    /* 0:Monday, ..., 6:Sunday. */
    /* We need 1 for Monday, 0 for Sunday. */
    first_weekday = (week_1stday + 1) % 7;
    printf("ret = %dn", ret);
    printf("sizeof(ret) = %Iun", sizeof(ret));
    printf("sizeof(week_1stday) = %Iun", sizeof(week_1stday));
    printf("sizeof(WCHAR) = %Iun", sizeof(WCHAR));
    printf("week_1stday = %lun", week_1stday);
    printf("first_weekday = %dn", first_weekday);
    return 0;
}