The Registration database

Starting with Windows 3.1, Each Windows system maintains a registration database file that records details about the DDE and OLE functions supported by the installed applications. The database is stored in file called REG.DAT in the \ WINDOWS directory. The file is a database that contains information that controls a variety of activities relating to data integration using DDE and OLE. The information contained in the REG.DAT database can be divided into four basic categories.

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Associations

Shell Operations

OLE Object Servers

DDE/OLE Automation