{
  There is no documented way to make a console application fullscreen.
  The following code works for both NT and Win9x.
  For win NT I used the undocumented SetConsoleDisplayMode and
  GetConsoleDisplayMode functions.
}
{
 function GetConsoleDisplayMode(var lpdwMode: DWORD): BOOL; stdcall;
  external 'kernel32.dll';
 // lpdwMode: address of variable for current value of display mode
}
function NT_GetConsoleDisplayMode(var lpdwMode: DWORD): Boolean;
type
 TGetConsoleDisplayMode = function(var lpdwMode: DWORD): BOOL;
 stdcall;
var
 hKernel: THandle;
 GetConsoleDisplayMode: TGetConsoleDisplayMode;
begin
 Result := False;
 hKernel := GetModuleHandle('kernel32.dll');
 if (hKernel > 0) then
 begin @GetConsoleDisplayMode :=
  GetProcAddress(hKernel, 'GetConsoleDisplayMode');
  if Assigned(GetConsoleDisplayMode) then
  begin
  Result := GetConsoleDisplayMode(lpdwMode);
  end;
 end;
end;
{
 function SetConsoleDisplayMode(hOut: THandle; // standard output handle
 dwNewMode: DWORD; // specifies the display mode
 var lpdwOldMode: DWORD // address of variable for previous value of display mode
 ): BOOL; stdcall; external 'kernel32.dll';
}
function NT_SetConsoleDisplayMode(hOut: THandle; dwNewMode: DWORD;
 var lpdwOldMode: DWORD): Boolean;
type
 TSetConsoleDisplayMode = function(hOut: THandle; dwNewMode: DWORD;
 var lpdwOldMode: DWORD): BOOL;
 stdcall;
var
 hKernel: THandle;
 SetConsoleDisplayMode: TSetConsoleDisplayMode;
begin
 Result := False;
 hKernel := GetModuleHandle('kernel32.dll');
 if (hKernel > 0) then
 begin @SetConsoleDisplayMode :=
  GetProcAddress(hKernel, 'SetConsoleDisplayMode');
  if Assigned(SetConsoleDisplayMode) then
  begin
  Result := SetConsoleDisplayMode(hOut, dwNewMode, lpdwOldMode);
  end;
 end;
end;
function GetConsoleWindow: THandle;
var
 S: AnsiString;
 C: Char;
begin
 Result := 0;
 Setlength(S, MAX_PATH + 1);
 if GetConsoleTitle(PChar(S), MAX_PATH) <> 0 then
 begin
  C := S[1];
  S[1] := '$';
  SetConsoleTitle(PChar(S));
  Result := FindWindow(nil, PChar(S));
  S[1] := C;
  SetConsoleTitle(PChar(S));
 end;
end;
function SetConsoleFullScreen(bFullScreen: Boolean): Boolean;
const
 MAGIC_CONSOLE_TOGGLE = 57359;
var
 dwOldMode: DWORD;
 dwNewMode: DWORD;
 hOut: THandle;
 hConsole: THandle;
begin
 if Win32Platform = VER_PLATFORM_WIN32_NT then
 begin
  dwNewMode := Ord(bFullScreen);
  NT_GetConsoleDisplayMode(dwOldMode);
  hOut := GetStdHandle(STD_OUTPUT_HANDLE);
  Result := NT_SetConsoleDisplayMode(hOut, dwNewMode, dwOldMode);
 end
 else
 begin
  hConsole := GetConsoleWindow;
  Result := hConsole <> 0;
  if Result then
  begin
  if bFullScreen then
  begin
  SendMessage(GetConsoleWindow, WM_COMMAND, MAGIC_CONSOLE_TOGGLE, 0);
  end
  else
  begin
  // Better solution than keybd_event under Win9X ?
  keybd_event(VK_MENU, MapVirtualKey(VK_MENU, 0), 0, 0);
  keybd_event(VK_RETURN, MapVirtualKey(VK_RETURN, 0), 0, 0);
  keybd_event(VK_RETURN, MapVirtualKey(VK_RETURN, 0), KEYEVENTF_KEYUP, 0);
  keybd_event(VK_MENU, MapVirtualKey(VK_MENU, 0), KEYEVENTF_KEYUP, 0);
  end;
  end;
 end;
end;
procedure TForm1.Button1Click(Sender: TObject);
var
 s: string;
begin
 AllocConsole;
 try
  SetConsoleFullScreen(True);
  Write('Hi, you are in full screen mode now. Type something [Return]: ');
  Readln(s);
  SetConsoleFullScreen(False);
  // ShowMessage(Format('You typed: "%s"', [s]));
 finally
  FreeConsole;
 end;
end;