This is a page where I link code that I have written that is publicly available. Most of my professional work has been proprietary, and I have not been much of a hobbyist programmer over my career (though I’m trying to change that), so this is a pretty short list so far. My GitHub is jhartzell42.


  • ledger-app-tezos (professional, mostly 2018): Although I am not personally a cryptocurrency enthusiast, during my time working for Obsidian Systems, it was part of my job to implement this app to support Tezos on the Ledger. Though it was a group project, I was the primary original author. The original target platform, the Ledger Nano S, had only 4K of RAM. I understand it has changed a lot since I originally worked on it.
  • compass (hobby, 2009-2010): This was a hobby project with a friend in college, and it is a bytecode interpreter for a Smalltalk-like language in C, combined with a compiler in Python and an “assembler” for the bytecode language also in C.