• After compilation your C program is put into a number
  of .o files, so all of these files must be combined into one
  file that is the executable version of the program. When
  the files are combined references between the files must
  be satisfied

• That is, when a procedure in file1.c calls a procedure in
  file2.c, the first procedure will eventually need to know
  that address of the second procedure. When file1.c is
  compiled this address is unknown so it is left as an
  external reference

• When the program is loaded, ld finds all the external
  references, determines where the routines and variables
  are actually located in memory and then goes back and
  fills in these addresses

• Loading also includes library files - your program can
  reference procedures that are in a library, when the
  program is loaded the procedures in the library must also
  be loaded, and thus the external references are satisfied

• The -l (ell) flag is used to specify the libraries that are
  to be loaded with a program, the standard C library is
  automatically loaded with your program

March 3, 1998

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