Source Manager

The Source Manager interacts between the application and the Source.   The Source Manager is usually implemented as a 32-bit or 64-bit DLL named TWAIN_32.DLL and TWAINDSM.DLL, respectively.

The 32-bit Source Manager is included with the Windows operating system and is usually found in the <drive>:\Windows folder under the name TWAIN_32.DLL.  For 64-bit Windows operating systems, there is no native 64-bit Source Manager.  Instead, the Source Manager must be installed, either by the TWAIN device or by your application.  The name of the file would be TWAINDSM.DLL.  This file can be downloaded from the Twain Working Group web-site (http://www.twain.org).

The first thing that a TWAIN application must do is load the Source Manager.  This entails making sure that the TWAIN_32.DLL or TWAINDSM.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.