Read the current code page of system

Problem/Question/Abstract:

How to read the code page of system?

Answer:

Sometimes in run-time you must detect the current values of code page.

To detect the code page of Windows operation system you must call the GetACP function from Windows API.

This function will return the value:
874 Thai
932 Japan
936 Chinese (PRC, Singapore)
949 Korean
950 Chinese (Taiwan, Hong Kong)
1200 Unicode (BMP of ISO 10646)
1250 Windows 3.1 Eastern European
1251 Windows 3.1 Cyrillic
1252 Windows 3.1 Latin 1 (US, Western Europe)
1253 Windows 3.1 Greek
1254 Windows 3.1 Turkish
1255 Hebrew
1256 Arabic
1257 Baltic

If you needs to read the code page of "DOS" sessions, you must call the GetOEMCP function from Windows API.
This function will return the value:

437 MS-DOS United States
708 Arabic (ASMO 708)
709 Arabic (ASMO 449+, BCON V4)
710 Arabic (Transparent Arabic)
720 Arabic (Transparent ASMO)
737 Greek (formerly 437G)
775 Baltic
850 MS-DOS Multilingual (Latin I)
852 MS-DOS Slavic (Latin II)
855 IBM Cyrillic (primarily Russian)
857 IBM Turkish
860 MS-DOS Portuguese
861 MS-DOS Icelandic
862 Hebrew
863 MS-DOS Canadian-French
864 Arabic
865 MS-DOS Nordic
866 MS-DOS Russian (former USSR)
869 IBM Modern Greek
874 Thai
932 Japan
936 Chinese (PRC, Singapore)
949 Korean
950 Chinese (Taiwan, Hong Kong)
1361 Korean (Johab)

Also you can check the valids of code page. For example,

if IsValidCodePage(866) then
  ShowMessage('Correct MS-DOS russian code page')