Dynamic Link Libraries

A dynamic link library (DLL, sometimes pronounced “dill”) is an executable module that may contain both application executables (compiled source code) and application resources. A DLL is similar in construction to a runtime library, except that it is not linked to the application during the compile process. Instead, DLLs are dynamically linked during execution when library resources—either executable routines or resources—are required.

DLLs have two important strengths:

A single DLL can be accessed by more than one application without being duplicated within each application.
Routines in DLLs can be revised and recompiled without modifying the programs using the called routines (assuming, of course, that the call-and-response format remains unchanged).

NOTE

Just as .EXE resources can be modified without recompilation, .DLL resources may also be edited, extracted, or updated without recompilation. Unfortunately, the current Visual C/C++ compiler does not support opening resources from .EXE or .DLL sources, although other compilers have managed this task without difficulty.