CODE teaches you about how computation can be structured out of circuits and switches and ultimately transistors. I now understand the fundamental nature of electronic computation.

UNIX taught me about the how an OS deals with hardware resources and the software that run on them. I now understand the environment in which my processes live as well as the structure of a process.

DDIA taught me about the structure of data, how databases operate on data through transactions, the difficulties of synchronization across databases, and the way data streaming works.