The OpenEdge Hive

** note: this topic is outdated, needs to be adjusted for ME and XP **
The API is not exactly the same for the different Windows versions so it is sometimes usefull to know which Windows version is running. However the differences may disappear when Windows 95/98 and Windows NT mature (or when add-ons are installed) so checking for the Windows version may become less interesting: you should prefer to check for features instead versions.
This procedure here shows what Windows version you are running providing it's a 32-bit version. These are:
* Windows 3.1 with win32s
* Windows 95
* Windows 95 OSR 2
* Windows 98
* NT 3.51
* NT 4.0
* Windows 2000
* Windows CE also runs a subset of WIN32 but CE isn't interesting for us.
The procedure also shows buildnumber and CSDversion. What a CSDversion is, is not always clear: on NT it's a string describing the latest installed Service Pack. On 95 it can be anything but CSDversion will be "a" if Service Pack 1 is installed.

{windows.i}
 
DEFINE VARIABLE lpVersionInfo AS MEMPTR.
DEFINE VARIABLE dwPlatformID AS INTEGER NO-UNDO.
DEFINE VARIABLE chPlatformID AS CHARACTER NO-UNDO.
DEFINE VARIABLE BuildNumber AS INTEGER NO-UNDO.
DEFINE VARIABLE MajorVersion AS INTEGER NO-UNDO.
DEFINE VARIABLE MinorVersion AS INTEGER NO-UNDO.
DEFINE VARIABLE ReturnValue  AS INTEGER NO-UNDO.
 
SET-SIZE(lpVersionInfo)   = 148.
PUT-LONG(lpVersionInfo,1) = 148.
RUN GetVersionExA IN hpApi( GET-POINTER-VALUE(lpVersionInfo), 
                            OUTPUT ReturnValue).
dwPlatformID = GET-LONG(lpVersionInfo,17).
 
CASE dwPlatformID :
  WHEN 0 THEN chPlatformID = "Win32s on Windows 3.1".
  WHEN 1 THEN chPlatformID = "Win32 on Windows 95 or 98".
  WHEN 2 THEN chPlatformID = "Win32 on Windows NT".
END.        
 
CASE dwPlatformID :
  WHEN 1 THEN BuildNumber = GET-SHORT(lpVersionInfo,13).
  WHEN 2 THEN BuildNumber = GET-LONG (lpVersionInfo,13).
  /* what about 'when 0' for 3.1 with win32s ?? */
END.
 
/* You have Windows 95 OSR 2 if:
     dwPlatformID=1
         and 
     LOWORD(BuildNumber)=1111 (probably hex??)
   Unfortunately I have not had a chance to test that.
*/
 
CASE dwPlatformID :
  WHEN 1 THEN DO:
                 MinorVersion = GET-BYTE(lpVersionInfo,15).
                 MajorVersion = GET-BYTE(lpVersionInfo,16).
              END.
  OTHERWISE DO:
                 MajorVersion = GET-LONG(lpVersionInfo, 5).
                 MinorVersion = GET-LONG(lpVersionInfo, 9).
              END.
END.
 
MESSAGE "MajorVersion=" MajorVersion SKIP
        "MinorVersion=" MinorVersion SKIP
        "BuildNumber="  BuildNumber SKIP
        "PlatformID="   chPlatFormId SKIP
        "CSDversion="   GET-STRING(lpVersionInfo,21) SKIP(2)
        "on NT, CSDversion contains version of latest Service Pack" SKIP
        "on 95/98, CSDversion contains arbitrary extra info, if any"
        VIEW-AS ALERT-BOX.
 
SET-SIZE(lpVersionInfo) = 0.

NT4 Terminal Server Edition

To check if you are running on Terminal Server Edition you can use function ValidateProductSuite("Terminal Server").
Old documentation suggested that this function would be added to the WIN32 API in Windows 2000. But newer documentation for Windows 2000 describes a new function VerifyVersionInfo - to be called with wSuiteMask = VER_SUITE_TERMINAL. We will see.
In the meantime you can write your own function ValidateProductSuite in Progress 4GL and some registry functions. An example is on page Disallowing multiple instances of your application.

A couple of convenient functions

FUNCTION RunningWindows95 RETURNS LOGICAL () :
  /* returns TRUE if you are running Windows 95 */
 
  DEFINE VARIABLE Win95         AS LOGICAL NO-UNDO.
  DEFINE VARIABLE lpVersionInfo AS MEMPTR.
  DEFINE VARIABLE dwPlatformID  AS INTEGER NO-UNDO.
  DEFINE VARIABLE MinorVersion  AS INTEGER NO-UNDO.
  DEFINE VARIABLE ReturnValue   AS INTEGER NO-UNDO.
 
  SET-SIZE(lpVersionInfo)   = 148.
  PUT-LONG(lpVersionInfo,1) = 148.
  RUN GetVersionExA IN hpApi( GET-POINTER-VALUE(lpVersionInfo), 
                              OUTPUT ReturnValue).
  dwPlatformID = GET-LONG(lpVersionInfo,17).
  MinorVersion = GET-BYTE(lpVersionInfo,15).
 
  Win95 = (dwPlatformId=1 AND MinorVersion=0).
 
  SET-SIZE(lpVersionInfo) = 0.
  RETURN Win95.
 
END FUNCTION.
 
FUNCTION RunningWindows98 RETURNS LOGICAL () :
  /* returns TRUE if you are running Windows 98 */
 
  DEFINE VARIABLE Win98         AS LOGICAL NO-UNDO.
  DEFINE VARIABLE lpVersionInfo AS MEMPTR.
  DEFINE VARIABLE dwPlatformID  AS INTEGER NO-UNDO.
  DEFINE VARIABLE MinorVersion  AS INTEGER NO-UNDO.
  DEFINE VARIABLE ReturnValue   AS INTEGER NO-UNDO.
 
  SET-SIZE(lpVersionInfo)   = 148.
  PUT-LONG(lpVersionInfo,1) = 148.
  RUN GetVersionExA IN hpApi( GET-POINTER-VALUE(lpVersionInfo), 
                              OUTPUT ReturnValue).
  dwPlatformID = GET-LONG(lpVersionInfo,17).
  MinorVersion = GET-BYTE(lpVersionInfo,15).
 
  Win98 = (dwPlatformId=1 AND MinorVersion=10).
 
  SET-SIZE(lpVersionInfo) = 0.
  RETURN Win98.
 
END FUNCTION.
 
FUNCTION RunningWindowsNT4 RETURNS LOGICAL () :
  /* returns TRUE if you are running Windows NT4.
     I have not had a chance to test this yet */
 
  DEFINE VARIABLE NT4           AS LOGICAL NO-UNDO.
  DEFINE VARIABLE lpVersionInfo AS MEMPTR.
  DEFINE VARIABLE dwPlatformID  AS INTEGER NO-UNDO.
  DEFINE VARIABLE MajorVersion  AS INTEGER NO-UNDO.
  DEFINE VARIABLE ReturnValue   AS INTEGER NO-UNDO.
 
  SET-SIZE(lpVersionInfo)   = 148.
  PUT-LONG(lpVersionInfo,1) = 148.
  RUN GetVersionExA IN hpApi( GET-POINTER-VALUE(lpVersionInfo), 
                              OUTPUT ReturnValue).
 
  dwPlatformID = GET-LONG(lpVersionInfo,17).
  MajorVersion = GET-BYTE(lpVersionInfo, 5).
 
  NT4 = (dwPlatformId=2 AND MajorVersion=4).
 
  SET-SIZE(lpVersionInfo) = 0.
  RETURN NT4.
 
END FUNCTION.
 
FUNCTION RunningWindows2000 RETURNS LOGICAL () :
  /* returns TRUE if you are running Windows 2000 */
 
  DEFINE VARIABLE Win2000       AS LOGICAL NO-UNDO.
  DEFINE VARIABLE lpVersionInfo AS MEMPTR.
  DEFINE VARIABLE dwPlatformID  AS INTEGER NO-UNDO.
  DEFINE VARIABLE MajorVersion  AS INTEGER NO-UNDO.
  DEFINE VARIABLE ReturnValue   AS INTEGER NO-UNDO.
 
  SET-SIZE(lpVersionInfo)   = 148.
  PUT-LONG(lpVersionInfo,1) = 148.
  RUN GetVersionExA IN hpApi( GET-POINTER-VALUE(lpVersionInfo), 
                              OUTPUT ReturnValue).
 
  dwPlatformID = GET-LONG(lpVersionInfo,17).
  MajorVersion = GET-BYTE(lpVersionInfo, 5).
 
  Win2000 = (dwPlatformId=2 AND MajorVersion=5).
 
  SET-SIZE(lpVersionInfo) = 0.
  RETURN Win2000.
 
END FUNCTION.

Another convenient function

Brad Long added this procedure which is indeed convenient.

FUNCTION WINGetVersion RETURNS CHARACTER () :
/*-----------------------------------------------------------------------------
  Purpose: Calls the WINAPI function GetVersionExA to determine the version
           of the Windows operating system that is running on the machine.
    Notes: Returns "95" for Windows 95, "98" for Windows 98, "NT" for Windows NT
           Returns "undef" if unable to determine platform.
------------------------------------------------------------------------------*/
 
    DEFINE VARIABLE v_version-buf AS MEMPTR.
    DEFINE VARIABLE v_platform-id AS INTEGER NO-UNDO.
    DEFINE VARIABLE v_platform-desc AS CHARACTER NO-UNDO.
    DEFINE VARIABLE v_major-version AS INTEGER NO-UNDO.
    DEFINE VARIABLE v_minor-version AS INTEGER NO-UNDO.
    DEFINE VARIABLE v_return-value  AS INTEGER NO-UNDO.
 
    SET-SIZE(v_version-buf)   = 148.
    PUT-LONG(v_version-buf,1) = 148.
 
    RUN GetVersionExA (INPUT GET-POINTER-VALUE(v_version-buf),
                       OUTPUT v_return-value).
 
    v_platform-id = GET-LONG(v_version-buf,17).
 
    CASE v_platform-id:
        WHEN 1 THEN DO:
            v_minor-version = GET-BYTE(v_version-buf,15).
            v_major-version = GET-BYTE(v_version-buf,16).
        END.
        OTHERWISE DO:
            v_major-version = GET-LONG(v_version-buf,5).
            v_minor-version = GET-LONG(v_version-buf,9).
        END.
    END.
 
    CASE v_platform-id:
        WHEN 0 THEN v_platform-desc = "3.1".
        WHEN 1 THEN
        DO:
            IF v_minor-version EQ 0 THEN v_platform-desc = "95".
            ELSE IF v_minor-version GT 0 THEN v_platform-desc = "98".
            ELSE v_platform-desc = "undef".
        END.
        WHEN 2 THEN
            v_platform-desc = "NT".
        OTHERWISE
            v_platform-desc = "undef".
    END.
 
    SET-SIZE(v_version-buf) = 0.
 
    RETURN v_platform-desc.
 
END FUNCTION.