the official specification for Nock, the assembly language used by the Urbit virtual machine, fits on a t-shirt: The Nock specification is only 200 words long It can be compressed to 371 bytes Nock is a low-level, homoiconic combinator language that's similar to JVM code. It's designed to be simple, and is interpreted by Vere. Hoon is the practical layer of Urbit, and it compiles itself to Nock, the simple layer.