What is errno used for?
PICTURE THIS: HOW TO EXPLAIN IT
IdeaErrors
HowWhat happens inside
Why they askShows real use
Simple meaning
C library error codes after failing calls.
WHY — Errors instead of guessing?
Why interviewers care about Errors:
Errors questions separate people
who only read docs from people who shipped.
Keep it short, concrete,
and tied to C++ work.
Stay structured
Name the idea, why it exists, then one short example.
Close cleanly
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1C library error codes
after failing calls.
- 2Why it exists
Not always thread-story simple historically.
- 3I prefer return codes
or exceptions in C++ APIs.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Say this line
“Not always thread-story simple historically.”
Break into beats
Notalwaysthreadstorysimplehistorically
Speaking order
2987408337471632900
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
C library error codes after failing calls. Not always thread-story simple historically.