C lib

That is a good question. I don't know the answer exactly, but I do know this. If it's a Borland C specific library, no. If it's a custom library, no. Any standard library that I have wanted to use has usually worked.

The easiest way to find out if a library you want to use is available is to create a basic program that you know is AC (for example TEST) and submit it with the include statement. If it's returns a runtime error, then you know the library is not available.

If you have any specific questions about specific libraries, you can ask here.

No. Gmp is not a standard library.