For example, in Windows with cyrylic MUI, system use cp1251 codepage for filesystem.
For working with international file- and pathnames I need know about codepage of filesystem.
My program use UTF-8 for internal working(Tk and other...) and I must encode names from filesystem codepage to internal UTF-8. I use utf-8 in Linux , but in Win32 I must using a lot of codepages for work with international filenames...