Introduction.

Specifies the character set used to display text in the drawing, set to the system code page when a new drawing is created.
The value of $DWGCODEPAGE can be uppercase or lowercase, statistically dos.. and iso8859-.. are lowercase, ANSI_.. and MAC-ROMAN are uppercase, but this isn't a law.
$DWGCODEPAGE values are not being clearly documented, I have to carry out reverse engineering (but read ascii file maybe can't define that) for know new values.
If older than DXF 12, there was not even the DWGCODEPAGE variable.
In this case is then set to "undefined" and the CAD program can not automatically convert the special characters, but this must be done manually with prompt command.
Since DXF 2006, this variable is writed but not evaluated.
Obviously I can not guarantee there are all values.

Table: $DWGCODEPAGE values.

DWGCODEPAGE
value
O.S. Localization
undefined
ascii Unix
iso8859-1 Unix Western Europe
iso8859-2 Unix Central Europe
iso8859-3 Unix Eastern Europe
iso8859-4 Unix Baltic
iso8859-5 Unix Cyrillic
iso8859-6 Unix Arabic
iso8859-7 Unix Greek
iso8859-8 Unix Hebrew
iso8859-9 Unix Turkish
dos437 DOS USA
dos850 DOS Western Europe
dos852 DOS Eastern Europe
dos855 IBM Russian
dos857 IBM Turkish
dos860 DOS Portuguese
dos861 DOS Icelandic
dos863 DOS Canadian French
dos864 DOS Arabic
dos865 DOS Norwegian
dos869 DOS Greek
dos932 DOS Japanese
big5 DOS Traditional Chinese
dos866 DOS Russian
gb2312 DOS Simplified Chinese
ksc5601 Korean Wansung
johab Korean Johab
mac-roman Mac
ansi_1250 Win Eastern Europe
ansi_1251 Win Russian
ansi_1252 Win Western Europe
ansi_1253 Win Greek
ansi_1254 Win Turkish
ansi_1255 Win Hebrew
ansi_1256 Win Arabic
ansi_1257 Win Baltic
ansi_874 Win Thai
ansi_932 Win Japanese
ansi_936 Win Simplified Chinese GB
ansi_949 Win Korean Wansung
ansi_950 Win Traditional Chinese big5
ansi_1361 Win Korean Johab
ansi_1200 Unicode
ansi_1258 Win Vietnamese