In both the Char and Character code commands, 4D documentation advises: "If the database is operating in Unicode mode (default mode for databases created with version 11 and higher of 4D), the command returns the Unicode UTF-16 code of the character (included between 1 and 65535)". For the majority of work with these two commands, it is convenient that between the character codes 32 and 127, the MacRoman character set and equivalent Unicode characters are the same. However once you are outside that code range, the MacRoman and UNICODE code differ greatly.
To see code comparison charts and complete listings of UNICODE characters (Unicode 5.2.0) you should refer to https://www.unicode.org/standard/standard.html. A second excellent reference of common Mac and Windows character sets and UNICODE can be found at https://www.alanwood.net/unicode/.