User Libraries, when to use?

[kla at physc1.byu.edu]

My understanding of libraries under unix is somewhat limited, but I haven't
seen any advantage to using libraries there. However, with MSC 5.1 I
understand that libraries are very useful because they only link in the
actual libraries needed by a particular program. Under unix it seems
that everything is linked in every time. If I am wrong about this I'd like
to know about it.