Character code input/output

• get_code(+Stream,?Code) Inputs a byte from Stream and unifies Code with the byte. After reaching the end of file, it unifies Code with -1.

• get_code(?Code) The same as the previous one except that the current input stream is used.

• put_code(+Stream,+Code) Outputs a byte Code to the stream Stream.

• put_code(+Code) Outputs a byte Code to the current output stream.