"\x{feff}" does not map to cp1256, <IN> line 1. And the character \x{feff} is displayed at the beginning of the file

FEFF is the unicode character code of the BOM (Byte Order Mark). You just have to ignore it (i.e skip over or remove it from the input).

(With UTF-8, the BOM has no real use (the byte order is always the same), but on Windows the BOM is generally used to identify the file as being unicode encoded.)