Source Manager

The Source Manager interacts between the application and the Source.   The Source Manager is usually implemented as a 16-bit or 32-bit DLL named TWAIN.DLL or TWAIN_32.DLL, respectively.  The Source Manager is usually included with the image device or can be gotten online at the TWAIN web site.

The first thing that a TWAIN application must do is load the Source Manager.  This entails making sure that the TWAIN_xx.DLL file exists, and an initialization function within the DLL is called.  The act of loading the Source Manager allows the application to communicate with any TWAIN Sources.  The Source Manager controls the interaction between the user application and the Source(s).

DTWAIN acts as a smart 'proxy' or helper between your application and the Source Manager.  There is no need for your application to know how to load or what functions to call when dealing with the Source Manager.