Looking for sample project in plain C

Hi all,

yes, there are so many projects running under Linux that come along with source.
On the other hand, probably I'm about to miss the forest for the trees.

I once wrote a Finite Element computer program to run under MacOS 8/9,
using only a command line interface (MPW).

Now I would like to port that code - which doesn't rely on special hardware.

The source code is plain C - I don't speak C++ (etc.).

It would help me to see an example of how to build and link libraries under Linux
from plain C source, in order to get a working program.

As a next step - not necessarily the same project - it would help me to have
a look at a project, in which use of parallel execution on several processors/cores
has been made - at best a program that as well is written in plain C.

Thank you !
Mike