Problems with OS

os.pullEvent = os.pullEventRaw

local w,h = term.getSize()

function printCentered (y,s)

  local x = math.floor((w - string.len(s)) /2)
  term.setCursorPos(x,y)
  term.clearLine()
  term.write(s)
end

--Draw Menu Function

local nOption = 1

local function drawMenu
  term.clear()
  term.setCursorPos(1,1)
  term.write("Rubik OS 0.1")

  term.setCursorPos(w-11,1)
  if nOption == 1 then
    term.write("Comandos")
  elseif nOption == 2 then
    term.write("Programas")
  elseif nOption == 3 then
    term.write("Apagar")
  elseif nOption == 4 then
    term.write("Desinstalar")
  else
    end
end
--Gui


term.clear()
local function drawFrontend()
  printCentered(math.floor(h/2) - 3, "")
  printCentered(math.floor(h/2) - 2, "Menu Inicio")}
  printCentered(math.floor(h/2) - 1, "")
  printCentered(math.floor(h/2) + 0, ((nOption == 1 and "[ Comandos ]") or "Comandos" )
  printCentered(math.floor(h/2) + 1, ((nOption == 2 and "[ Programas]") or "Programas")
  printCentered(math.floor(h/2) + 2, ((nOption == 3 and "[ Apagar ]") or  "Apagar"
  printCentered(math.floor(h/2) + 3, ((nOption == 4 and "[ Desinstalar "] or "Desinstalar"
end

--Display

drawMenu()
drawFrontend()

while true do
  local e,p = os.pullEvent()
    if e == "key" then
	  local key = p
	  if key == 17 od key == 2000 then
	  
	    if  nOption > 1 then
		  nOption = nOption - 1
		  drawMenu()
		  drawFrontend()
	    end
	  elseif key == 31 or key == 208 then
	    if nOption < 4 then
		  nOption = nOption + 1
		  drawMenu()
		  drawFrontend()
	    end
	  end
   elseif key == 28 then
	  break
   end
end
end
term.clear()

--Conditions
if nOption == 1 then
  shell.run("os/.command"
elseif nOption == 2 then
  shell.run("os/.programs")  
elseif nOption == 3 then
  os.shutdown()
else
  shell.run("os/.uninstall")
end