btw- you should never hook a battery directly (without a resistor in series) to any LED as you have done. Most of the time you destroy the LED when you do. You lucked out.
It is not a homework problem.
I found a bunch of these in a box and had to identify all of the pins.
I used a 1k resistor. forgot to draw it.
My guess is that it is common cathode. Is it?
Since these always run on a positive supply, it is a common anode. The seven-seg decoder grounds those segments to be lit. Get the part number off it and Google it. You may find a data sheet.
Thank you. I just checked again but do not see any part number on the device or I would have looked up the data sheet.
I was going to run these off of a 4511 to experiment with. The parts list I have calls for a common cathode so I may not be able to use them in this case.