what is a " *.so " file?

are .so files related to static libraries?

No. .so files are libraries meant to be linked dynamically.

ok , just learnt what are static and dynamic libs.. if i know the loc of a .so file. how do i link it in GCC?

let me elaborate...
i have a libacml.a file and a libacml.so file ,both in the same directory.
and at the prompt :

Code:

---

    gcc prog.c  -L<actual path to this dir >  -lacml

---

which one will it link and how do i specify which one to be linked.

I believe it will choose dynamic linking when possible unless you give gcc the -static option