Like most modern operating systems, Microsoft Windows supports
shared libraries , collections of code which can be used by
multiple processes while only being loaded once into memory.
Windows terms its shared libraries Dynamic-link libraries Most
core Windows functionality is contained within Native
Applications and a set of DLLs, which together implement the
various subsystems under which code can run (Win32 , Microsoft
Windows Services for UNIX (SUA), Virtual DOS machine ,
etc.).Each subsystem defines and implements a large number of
functions, or Application programming interfaces (APIs),which
programs running under the subsystems can call.These APIs are
exported by, and in many cases implemented in,one or more DLLs
specific to the subsystem. Many other DLLs exist within Windows
as components of specific programs or services that are provided
with the operating system, andthird-party programs or services
added to the system can come with DLLs of their own as
well.These are not considered library files, as