3
The Machine: How Code Actually Runs
From source code down to silicon and out across the network.
Why it matters when agents do the typing
Every layer of the stack leaks into the layers above it, and those leaks decide speed, cost and correctness. When a service slows down, runs out of memory or corrupts data in the middle of the night, the person paged has to reason from the code down to the machine. Knowing the stack is how you predict what code will do before it runs and explain what it did afterward.
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Depth: explain
Hardware and the Operating System
What the CPU, memory, storage and operating system actually do when a program runs, and why their costs differ by orders of magnitude.
A mistake it teaches you to catch: A whole file or table loaded into memory when the job needed to stream it, which works in testing and crashes on real data.
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Core 5
Depth: explain
Languages, Compilers and Runtimes
How source code becomes running behavior: parsing, compilation, interpretation, type systems, memory management and concurrency models.
A mistake it teaches you to catch: A blocking call inside an async handler that stalls every other request on the event loop.
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Core 6
Depth: do
Representing Numbers, Text and Time
How computers store integers, decimals, text and timestamps, and the silent errors each representation invites.
A mistake it teaches you to catch: Money stored and calculated as floating-point numbers, producing totals that are off by a cent.
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Depth: explain
Networks and Protocols
How machines exchange data, from packets and routing up through DNS, TCP, TLS and HTTP.
A mistake it teaches you to catch: A state-changing action exposed as a GET request, which link prefetchers and crawlers will trigger.