[Haskell-cafe] ByteString questions

Hello, 1) I noticed there is no "open" function in Data.ByteString. So when I call writeFile or readFile is there an implicit open? 2) For both readFile and writeFile, the first parameter is of type FilePath (which is of course alliased to just String). In any case, for Windows and POSIX OS's like Linux can read and write to a serial device like RS232 by specfiying the device path, e.g. /dev/tty01? Thanks, Vasili