CE's Blog

The code page system is a means of representing extended character sets in binary form without leaving the 8 (or 7) Bit based storage and API conventions. There are more than a hundred different code pages, and depending on your system, more or less are supported by the Win32 API.

If you are planning to handle different encodings within your application, it might be useful to know which code pages are available on your system, so you can encode/decode text based on them. Not every System supports every code page though. Just recently I found that an English Windows Mobile 5 would support CP 1252, but not the (very common) Latin-1 character set.
Especially when converting from or to some less common code pages it can be worthwhile to check whether or not there is built in support available.

To enumerate all the installed Code Pages, you can use the EnumSystemCodePages API. It accepts a callback function as a parameter and a flag that specifies whether to enumerate all installed or all supported code pages. Although the docs are not clear about the latter, it seems that the installed code pages are the pages which are ready for conversion, while the supported code pages seem to contain also pages which fail to convert any characters.

Strangely, the callback function gets called with the code page number in string representation, so you might want to do  a _ttoi() in order to get the code page number in use with other APIs.

CAtlArray<CPINFOEX> asCodePagesInstalled;
 
BOOL CALLBACK EnumCodePagesInstalledProc( LPTSTR szCodePageString )
{
    CPINFOEX cpInfoEx;
     if ( 0 != GetCPInfoEx( _ttoi( szCodePageString ), 0, &cpInfoEx ) )
         asCodePagesInstalled.Add( cpInfoEx );
    return TRUE;
}
//...
EnumSystemCodePages( EnumCodePagesInstalledProc, CP_INSTALLED );
//...

It is difficult to determine the lowest common denominator of all code pages supported on every system, and it gets even more complicated when Win 9x or mobile versions need to be supported. So in case your application will demand more than just the bare minimum conversions, you might want to resort to an external library, such as ICU or libiconv.