If a function doesn't have a 'need to know', it shouldn't automatically get a 'right to know'. The only thing exposed in queue.h is the names and parameters (data types) for the insert and remove functions. What possible good can come from that? Better, in my view, to define everything related to the queue implementation inside queue.c. But that allows other files to include queue.h and gain some knowledge about how the queue is implemented. It might be tempting to define the queue data structure and the queue size along with the head and tail pointers in queue.h. Clearly, the queue structure and head/tail pointers would be file static variables. ADC -> Queue -> Application No global variables! I don't have such heartburn over file static variables where the variable is only visible to functions in the same. I would rather place the ADC value in a managed container like a queue where the queue structure belongs to, and is only visible by, the queue handler.

Ownership is a problem, contamination is a possible result.

Reent.h no such file