Too long without yielding.

Every time I run the programme it always comes up with "programme:16: too long without yielding" and I don't know what it means, I have tried a lot of things and it doesn't work s it would be great if you knew, also there is the code and thanks.

local pos = 13
mon = peripheral.wrap("right")
mon.clear()
mon.setTextScale(2)
while true do
if pos==-6 then
pos=13
end
mon.clear()
mon.setCursorPos(7,1)
mon.write("The Zoo")
pos = pos-1
end

Split into new topic.

It means your program isn't yielding to allow other computers to run. Put a sleep(0.5) right before the `end` near the bottom of your program.

thanks it now works