Live coding
C Interview Copilot
C interviews strip the round back to memory: who allocated it, who frees it, and what the standard actually promises about the code you just wrote.
The round
What a C interview actually looks like
Embedded, kernel and firmware loops still run C screens, and they are unusually concrete: implement a string routine, walk a linked list, describe what a pointer cast does to alignment. The interviewer is checking whether you reason about memory deliberately or by habit, so expect to be asked what happens on the failure path of every allocation you write. Embedded teams add a constraint the answer has to respect — no dynamic allocation at all, or a fixed stack budget — and the follow-up asks how your solution changes when malloc is off the table.
What you get back
Solutions allocate and free in matched pairs, check every allocation, and avoid the unsafe standard-library calls that a reviewer would flag. Buffer sizes are explicit rather than assumed, and the answer says what happens at the boundary. Where behaviour is undefined rather than merely unspecified, the response names it instead of relying on what a particular compiler happens to do.
Example prompts
Questions people are actually asked
Send the transcript straight to the coding surface, or snip the problem off the screen.
Implement strdup without using the library version.
Reverse a singly linked list in place.
What is wrong with returning a pointer to a local array?
Where candidates lose points
C-specific traps
Off-by-one on the null terminator
Sizing a buffer to the string length rather than length plus one is the classic C screen bug, and it is set in almost every string question.
Assuming compiler behaviour
Describing undefined behaviour as what your compiler does is treated as a wrong answer even when the program appears to work.
Unchecked malloc
A missing null check on allocation reads as production-unsafe code, and interviewers for systems teams look for it specifically.
Three surfaces
One workspace, three kinds of round
Chat
Behavioral rounds and the “tell me about a time” half of a technical screen, in your own voice.
Live coding
A structured solution with the reasoning attached, so you can talk through the code while you write it.
System design
Architecture answers with the diagram rendered inline, not described in prose.
Choosing a model
Keep reading
Related
C++ Interview Copilot
Live help for C++ interviews: RAII and smart pointers, move semantics, and STL choices explained with the complexity that follows from them.
Rust Interview Copilot
Live help for Rust interviews: ownership and lifetimes explained as you go, plus solutions that compile rather than fight the borrow checker.
Go Interview Copilot
Live help for Go interviews: goroutines and channels answered precisely, idiomatic error handling, and solutions that look like reviewed Go.
System design copilot
Architecture rounds with the diagram rendered inside the answer.
Platform setup: hackerrank · codility