XKCD Geek Code
This page documents the XKCD geek code as listed on the Denizens page.
A geek code is generated by constructing an expression based on the rules for a subset of the code and appending all such expressions. Omission of an expression means that you are either not advertising knowledge or that you know nothing of said thing.
 Project Euler
Project Euler is a series of mathematical challenges typically solved by algorithm development. Many of these require deep mathematical insights in order to work out and, as a result, the completion of a Euler project is worn as a badge of honor by many denizens. This is listed in one's geek code as the letters "PE", followed by a number (or series of numbers) at the very beginning. Examples:
PE20 would mean that one has completed problem 20 on Project Euler PE1-20 would mean that one has completed problems 1-20 inclusive on Project Euler. PE1,5,7,9-20 would mean one has...well...you get the picture.
 Last Question
The Last Question is an Asimov short story. It was originally introduced to channel by xkcd and is a point of interest among denizens as it raises interesting questions about computational evolution and the eventual fate of man. This is symbolized in geek code by "LQ", followed by a numeral between 1-10 for how much you liked it.
cerise has not done Project Euler, but has read (and loved) The Last Question. His Geek Code might be LQ10.
xkcd has completed 36 Euler projects and loved The Last Question. His Geek Code might be PE1-36LQ10.