external data segments

external sub-routines

data located in other procedure

all of these

relocating loader itself

linker

assembler

macro processor

it makes implementation of lexical analysis and syntax analysis easier

syntax directed translations can be written for intermediate code generation

it enhances the portability of the front end of the compiler

it is not possible to generate code for real machines directly from high level language programs

non reusable module

serially reusable module

re-enterable module

all of these

( L∪ D ) *

L ( L ∪ D)*

( L . D )*

L . ( L . D )*