Question

Most of the time in C programming it seems that there will be one header file (.h) per code file (.c), for the function prototypes at least.

When would it be appropriate to not have a header file for a code file?

Answer 1

There’s a few use cases for this. The most obvious is that your main program rarely needs a header file.

The second is where you don’t have one header for each C file. I’ve put together libraries before (let’s say a BTree library for the purposes of this answer) where each individual function is in its own source file but there’s a library-wide header file, something like:

btree.h
btree_priv.h
btreeInit.c
btreeDestroy.c
btreeConfig.c

and so on. The private header file is for stuff that need to be shared between the code but is not to be published in the API.