Summary
For INT 21h Function 65h, an unavailable country/code-page pair should report error 2. The MS-DOS 3.3 Programmer's Reference says that a mismatched or invalid country/code-page pair returns AX=2, while CX below 5 returns error 1.
In FDOS/kernel commit d6791add2043c9d7b584d840a8ffaf8829fd2bdc, DosGetData() passes requests with no matching loaded NLS package to mux65(). The default MUX-14 handler, syscall_MUX14(), returns DE_INVLDFUNC when searchPackage() cannot find the requested pair. That error is propagated, so the unavailable-data path reports AX=1 instead of the documented AX=2.
Minimal call
With no matching NLS package/provider loaded:
INT 21hAH=65h, AL=02hBX=0437hDX=FFFEh (unavailable country ID)CX=0005h (minimum valid buffer size)ES:DI points to a valid 5-byte buffer
Expected: carry set and AX=0002h.
Observed from the default source path at the commit above: carry set and AX=0001h (DE_INVLDFUNC).
Reference
Microsoft, MS-DOS Version 3.3 Programmer's Reference, “Get Extended Country Information (Function 65H),” Return and Comments sections: https://www.pcjs.org/documents/books/mspl13/msdos/dosref33/
Summary
For INT 21h Function 65h, an unavailable country/code-page pair should report error 2. The MS-DOS 3.3 Programmer's Reference says that a mismatched or invalid country/code-page pair returns AX=2, while CX below 5 returns error 1.
In
FDOS/kernelcommitd6791add2043c9d7b584d840a8ffaf8829fd2bdc,DosGetData()passes requests with no matching loaded NLS package tomux65(). The default MUX-14 handler,syscall_MUX14(), returnsDE_INVLDFUNCwhensearchPackage()cannot find the requested pair. That error is propagated, so the unavailable-data path reports AX=1 instead of the documented AX=2.Minimal call
With no matching NLS package/provider loaded:
INT 21hAH=65h,AL=02hBX=0437hDX=FFFEh(unavailable country ID)CX=0005h(minimum valid buffer size)ES:DIpoints to a valid 5-byte bufferExpected: carry set and
AX=0002h.Observed from the default source path at the commit above: carry set and
AX=0001h(DE_INVLDFUNC).Reference
Microsoft, MS-DOS Version 3.3 Programmer's Reference, “Get Extended Country Information (Function 65H),” Return and Comments sections: https://www.pcjs.org/documents/books/mspl13/msdos/dosref33/