You can't rely on the OS version number to tell you whether the memory card is 
supported or not. True, you need at least version 4.0 of the SDK to compile a 
program that uses the VFS manager - but there have been devices running an 
older version of the OS (e.g., 3.0.1H) that nevertheless supported memory cards 
with some custom libraries. See, for instance, this

http://homepage.ntlworld.com/john.r.wells/VFS_Tut.htm

If you disassemble some code that uses the VFS Manager, you'll see that all the 
functions are basically compiled to calls to the undocumented function 
FileSystemDispatch (system trap 0xA348), so, theoretically, anybody could 
provide their own VFS Manager interface by patching this system trap on the 
earlier versions of the OS.

If you want to know whether the VFS Manager is present on a particular device, 
use the method described on the Web page mentioned above.

Regards,
Vesselin
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