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📜 WAYPOINT LESSON

State-table discipline

⭐⭐⭐ advanced⏳ 10 min read📍 Lesson 165 of 256

One row per event, one column per changing value — and the two misdirections (dead variables, frozen values) that break traces.

Tracing is a skill with technique. The exam's hardest tracing items share three properties: many small state changes, at least one misdirection (a variable that looks important but is dead), and a boundary case in the middle of the loop, not at the start.

The state-table discipline:

  1. One row per event (a call, an iteration, an assignment to a reference) — not per line.
  2. One column per piece of state that can change. Include the object graph when references move: a → obj1 is a row of its own.
  3. Never recompute a column from memory; read the row above and apply exactly the code you see.
  4. The answer is a cell in the table. If it is not, you traced the wrong thing.

Watch for the two classic misdirections: a variable updated but never read (dead), and a variable read but never updated after the first iteration (frozen).