I'm a complete techno-nerd--when I'm not writing books, which I do for the fun of it, I write code. Mostly what I write these days are GTK+-based applications like aplwrap, an environment for GNU APL; gf3, a GTK+-based replacement for xfig with embedded Python; and visualise, a function visualiser. I've also written aplplot, that adds visualisation capability to GNU APL, and clc, a vector/matrix oriented command-line calculator. (All of these can be found at https://github.com/ChrisMoller)
In past lives, I've written ports of FSF binutils and gcc and a fair amount of work in Linux Loadable Kernel Modules. I've also written simulators for various processor architectures.