Shared libraries allow the loading of commonly used portions of program 
code from one location.  Normally, when a program is generated from source 
code, all the required machine code generated by the compiler is linked 
together into a single exectuable.<p>

Many programs, however, use common functions and routines that are defined 
as part of the C "standard library".  With shared libraries, these 
functions (and others by design of programmers) don't get linked into the
executable when the program is built; rather, they are kept in a central
location.  When the program is run, a special program called ld.so loads
the requested functions from the central repository.  The net result is a
dramatic decrease in the size of executable files.



Fred Dushin
 fadushin@top.cis.syr.edu