Are you saying that the circuit board is sending output via serial port to a computer and you need to save this output??

If you're working with small memory space requirements, I'd checkout sqlite. You can always work with ini files or csv files as well. MySQL is a good choice if it will work within the constraints that you might be under.

The thing about C is that you have to remember to close file pointers, database pointers, and manage your memory. A lot of higher level languages take care of these things.

I would suggest contacting RonWilder (here on the WarriorForum), he is pretty knowledgeable in this space (working with Micro Controllers, etc), and he should be able to give you pointers that will help you get what you're looking for

Your best bet will probably be MySQL it has libraries for most OS's.

Yeah. Even i am also developing programs using C and when there is need for database connectivity than i am using MySQL because it's very easy to use and implement. Just go through queries of that, it's very easy and simple.

I'm not a C programmer, but I've actually used the C API for MySQL with Python. It's pretty easy.