clock

-- Get hold of the canvas
local interface = peripheral.wrap("back")
local canvas = interface.canvas()
-- And add a rectangle
local rect = canvas.addRectangle(0, 0, 100, 100, 0xFF0000FF)

rect.setSize(250, 30)
rect.setAlpha(100) -- Let's make this see through

local text = canvas.addText({ x = 5, y = 5 }, "")
text.setScale(3)
while true do
  text.setText("Time is " .. textutils.formatTime(os.time()))
  sleep(1)
end