{ 
   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;