Although I wouldn't really know for what you would like to use these 
features, they are provided for ISO complicancy.
- char_conversion(+CharIn, 
+CharOut)
 - 
Define that term-input (see read_term/3) 
maps each character read as
CharIn to the character CharOut. Character 
conversion is only executed if the prolog-flag 
char_conversion 
is set to
true and not inside quoted atoms or strings. The initial 
table maps each character onto itself. See also current_char_conversion/2.
 - current_char_conversion(?CharIn, 
?CharOut)
 - 
Queries the current character conversion-table. See char_conversion/2 
for details.