Source : Free On-Line Dictionary of Computing

linker
     
         (linkage editor, link loader) A program
        that combines one or more files containing {object code} from
        separately compiled program {modules} into a single file
        containing loadable or executable code
     
        This process involves resolving references between the
        {modules} and fixing the {relocation} information used by the
        operating system {kernel} when loading the file into memory to
        run it.
     
        Under {Unix}, the linker is called "ld" and {object files}
        have filename extension .o (object), .so (shared object), or
        .lib ({library}), and the resulting {executable} is called
        "a.out" by default.
     
        (2001-10-13)