How does a c-compiler recognizes system-calls?

Question

Let's say we want to create a socket using the "socket"-function. How does the compiler know that it has to invoke a system call for that corresponding function? Is there any internal table that records with functions belong to a specific set of library?

Answer 1

The usual method is this:

Your platform's library includes a function called socket that contains the actual code needed to make a system call on your platform. The compiler reads in a header file that tells it that this function exists, the linker connects the compiled code to that function, and the library's implementation of that function makes the actual system call.