Detect System Endianness in C

Context

Byte order matters when working with binary protocols, file formats, embedded systems, and low-level debugging. Interviewers ask this question to test whether you understand how integers are stored in memory and how C exposes raw memory.

Core Question

Explain how you would determine whether a machine is little-endian or big-endian in C.

Your answer should cover:

1. What endianness means for multi-byte values.
2. How to inspect memory in C to determine byte order.
3. Why checking the first byte of an integer works.
4. Any portability or safety considerations when writing this code.

Scope Guidance

The interviewer is usually looking for a short low-level explanation plus a small C example. You should be able to describe the memory layout of a value like 0x00000001, explain the role of pointers or byte access, and mention that this technique detects the host machine's runtime representation rather than changing it.