Powering LED's : use a resistor or not?

Hello,

I was looking at the 8/8/8 Tutorial number 2 about hooking up an LED to a digital output. My question is this: Why isn't there a need for resistor to be placed before the LED so it doesn't burn out? On other IO boards cockpit builders use, to power a LED requires a resistor to restrict current so the LED doesn't burn out. Is there some internal circuitry in the 8/8/8 to protect a LED from burning out? Does the 0/16/16 act the same way?

Thank you.
Shawn

The 8/8/8 outputs 5 volts which isn't enough to burn out an LED.

The 0/16/16 it very different it doesn't have it's own power source. It switches to ground on the power source you supply.

Here are the differences of the boards side by side:
http://www.phidgetsusa.com/tutorials...ifferences.asp

Matt