Although I wouldn't really know for what you would like to use these 
features, they are provided for ISO compliance.
- [ISO]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
trueand not inside quoted atoms or strings. The initial 
table maps each character onto itself. See also current_char_conversion/2.
- [ISO]current_char_conversion(?CharIn, 
?CharOut)
- 
Queries the current character conversion-table. See char_conversion/2 
for details.