Determining the Version of MS-DOS from a Windows App

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) for Windows versions 3.0 and 3.1

SUMMARY

There are at least three ways for an application developed for Windows version 3.x to determine the version of MS-DOS that is running on the system. Both the first and second methods require placing a few lines of inline assembler code into the application. The second method requires MS- DOS version 5.0. The third method requires changing the GetVersion() function prototype in the WINDOWS.H header file distributed with the Microsoft Windows SDK version 3.0 (this change is not necessary if the Microsoft Windows SDK version 3.1 is being used).

Even though it is necessary to modify the Windows 3.0 header file, the third method is the most removed from the hardware and can be considered the most portable. The other two methods assume an underlying Intel 80x86 architecture (or emulation).

MORE INFORMATION

Method 1

This method requires only a few lines of inline assembler code and a call to the DOS3Call() function. The following code fragment demonstrates this technique:

   VOID FAR PASCAL DOS3Call(VOID);   // Use instead of INT 21h
   int nMajor;                       // MS-DOS major version
   int nMinor;                       // MS-DOS minor version, revision
   int nOEMNumber;                   // OEM serial number
   static char szUserMsg[80];        // holds user message

   _asm
     {
        mov   ax, 0x3000        ; Get MS-DOS version
        call  DOS3Call
        mov   nMajor, al        ; Save major number
        mov   nMinor, ah        ; Save minor version number
        mov   nOEMNumber, bh    ; Save OEM Serial number
     }

   wsprintf(szUserMsg,
            "Running on MS-DOS %d.%d OEM Serial Number %d",
            nMajor, nMinor, nOEMNumber);
   MessageBox(hWnd, szUserMsg, "MS-DOS Version", MB_OK);

Method 2

This method requires only a few lines of inline assembler code and a call to the DOS3Call() function. Additionally, it requires that MS-DOS version 5.0 is running on the system. While this function does not report the OEM serial number, it does report whether MS-DOS is in ROM or in HMA (the High Memory Area). Also the MS-DOS version returned by this method is unaffected by the SETVER command. The following code fragment demonstrates this technique:

   #define DOSINROM 0x08
   #define DOSINHMA 0x10

   int nMajor    = 0;
   int nMinor    = 0;
   int nRevision = 0;
   int nDOSFlag  = 0;
   static char msg[120];

   _asm
     {
         mov   ax, 0x3306        ; Get MS-DOS version
         call  DOS3Call
         mov   nMajor, bl        ; Save major number
         mov   nMinor, bh        ; Save minor version number
         mov   nRevision, dl     ; Revision num in low 3 bits
         mov   nDOSFlag, dh      ; MS-DOS version flags
     }

   wsprintf(msg,
            "Running on MS-DOS %s %s version %d.%d revision %d ",
            (LPSTR) (nDOSFlag & DOSINROM ? "in ROM " : ""),
            (LPSTR) (nDOSFlag & DOSINHMA ? "in HMA " : ""),
            nMajor, nMinor, (nRevision & 0x03));
   MessageBox(hWnd, msg, "MS-DOS Version", MB_OK);

Important Note for Methods 1 and 2

The DOS3Call() function must be prototyped. In assembly language, the appropriate prototype is as follows:

   extrn DOS3CALL: far

Also note that the use of FAR and PASCAL in the definition of DOS3Call() requires use of WINDOWS.H, since these macros are defined there.

Method 3

The last method involves making a slight modification to the Windows SDK version 3.0 header file, WINDOWS.H. To retrieve the MS-DOS version, change the return type in the function prototype of the GetVersion function call from a WORD to a DWORD. The modified prototype should resemble the following:

   DWORD FAR PASCAL GetVersion(void);

The following code fragment demonstrates how to use the GetVersion() function to display both the MS-DOS version and the Windows version numbers:

   DWORD dwVersion;
   char szUserMsg[80];

   dwVersion = GetVersion();
   wsprintf(szUserMsg,
            "Window version %d.%d. MS-DOS version %d.%d",
            LOBYTE(LOWORD(dwVersion)), HIBYTE(LOWORD(dwVersion)),
            HIBYTE(HIWORD(dwVersion)), LOBYTE(HIWORD(dwVersion)));

   MessageBox(hWnd, szUserMsg, "GetVersion", MB_OK);