It affects the C++ library functions and optional also the C standard library functions. See
http://www.cplusplus.com/reference/locale/locale/global/[
^].
To set a locale for the Windows API functions, use
SetThreadLocale[
^].
For MFC it depends. Some MFC controls like
CComboBox
provide a
SetLocale
member function to select a different locale. The
CString
classes use the standard C libraries for formatting and are therefore affected by
setlocale
.