Theory Card 078 — Error Detection / Structure
Research lens
Error detection relies on having reference points that make mismatches visible. In the Structure stage of BASIC, the goal is to externalize a plan, invariant, or architecture. That makes this concept especially relevant here, because it shapes how much mental work the candidate is trying to carry at once and what gets made explicit.
Why it matters in SWE interviews
In coding rounds this means edge cases and invariants; in design rounds it means bottlenecks, outages, and abuse cases. Structure and Check create those reference points by naming what should happen before execution is complete. In practice, Structure is where the candidate should ask: What is the sequence, helper structure, invariant, or component map that will carry the solution? That question acts like a cognitive boundary. It protects the answer from turning into an unstructured search.
BASIC move
A strong move here is to make the plan visible before full execution. For Error Detection, that means deliberately naming the important units instead of juggling them implicitly. The interviewer sees cleaner reasoning, and the candidate benefits from reduces hidden-state thinking and makes reasoning inspectable.
Common miss
The miss is discovering mistakes only after the interviewer asks a pointed follow-up. When that happens, the candidate usually feels busy, but the answer is actually becoming less inspectable.
Practice prompt
“While practicing, pause at the Structure step and explain how Error Detection changes the way you would handle the prompt.”