Определение операционной системы

const
  { operating system constants }
  cOsUnknown = -1;
  cOsWin95 = 0;
  cOsWin98 = 1;
  cOsWin98SE = 2;
  cOsWinME = 3;
  cOsWinNT = 4;
  cOsWin2000 = 5;
  cOsWhistler = 6;

function GetOperatingSystem : integer;
var
  osVerInfo: TOSVersionInfo;
  majorVer, minorVer: Integer;
begin
  result := cOsUnknown;
  { set operating system type flag }
  osVerInfo.dwOSVersionInfoSize := SizeOf(TOSVersionInfo);
  if GetVersionEx(osVerInfo) then
  begin
    majorVer := osVerInfo.dwMajorVersion;
    minorVer := osVerInfo.dwMinorVersion;
    case osVerInfo.dwPlatformId of
      VER_PLATFORM_WIN32_NT : { Windows NT/2000 }
      begin
        if majorVer <= 4 then
          result := cOsWinNT
        else
        if (majorVer = 5) and (minorVer= 0) then
          result := cOsWin2000
        else
        if (majorVer = 5) and (minorVer = 1) then
          result := cOsWhistler
        else
          result := cOsUnknown;
      end;
      VER_PLATFORM_WIN32_WINDOWS : { Windows 9x/ME }
      begin
        if (majorVer = 4) and (minorVer = 0) then
          result := cOsWin95
        else
        if (majorVer = 4) and (minorVer = 10) then
        begin
          if osVerInfo.szCSDVersion[1] = 'A' then
            result := cOsWin98SE
          else
            result := cOsWin98;
        end
        else
        if (majorVer = 4) and (minorVer = 90) then
          result := cOsWinME
        else
          result := cOsUnknown;
      end;
      else
        result := cOsUnknown;
    end;
  end
  else
    result := cOsUnknown;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  ShowMessage(IntToStr(GetOperatingSystem));
end;

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