Easy Language Question 11 of 208

What is a header guard?

C++ interview set · Speak this in 60–90 seconds · Faridabad & Delhi NCR

QuestionEmbed query

SearchCompany docs

LLMAnswer with sources

Ifndef define endif, or pragma once, stops a header from being included twice in one translation unit.

Why interviewers care about Language:

Language 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.

Before you speak the answer, walk the interviewer through these steps:

1
Ifndef define endif, or
pragma once, stops a header from being included twice in one translation unit.
2
Without it I get
redefinition errors.
3
I still design headers
to be idempotent.
4
Give an example
One tiny concrete case you can say aloud.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

Here's a short line you can speak, broken into clear beats:

Say this line

“Without it I get redefinition errors.”

Break into beats

WithoutitIgetredefinitionerrors

Speaking order

2987408337471632900

Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

Ifndef define endif, or pragma once, stops a header from being included twice in one translation unit. Without it I get redefinition errors.