INF: Determining the Version of MS-DOS from a Windows App

ID Number: Q80783

3.00 3.10

WINDOWS

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 Software Development Kit (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

Use the DOS3Call fucntion instead of making a direct call to MS-DOS

INT 21h. The DOS3Call function runs a little faster than the equivalent

INT 21h call under Windows and it ensures that the interrupt will be

handled correctly under Windows.

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);

It is not necessary to make the above change to the version of

the WINDOWS.H file included with the Windows SDK version 3.1.

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);

Additional reference words: 3.00 3.10 3.x