The UNIX and Windows operating systems support the use of an executable file that contains compiled functions or routines that can be linked to an application at runtime rather than at build time. This executable file is called a shared object or shared library on UNIX and a dynamic link library (DLL) in Windows. This dynamic linking capability promotes a building block approach to application development; third-party software packages provide much of their functionality in shared libraries. It also makes function upgrades more easily available to applications that use them.
Throughout this section, the term "shared library" is used when a statement is applicable to both the UNIX and Windows systems. "UNIX shared library" is used if a statement is applicable only to UNIX; "DLL" is used for statements applicable only to Windows.
