The -llibrary option looks for the specified file
(with a .a extension) and scans this library archive for unresolved
symbols when linking.
The directories searched include several
standard system directories, plus any that you specify with -L.
The only difference between using an -l option (e.g.,
-lmylib) and specifying a file name on the command line (e.g.,
mylib.a) is that the compiler will
search for the library specified using -l in several directories, as
specified by the -L option.