The registration database is a file called REG.DAT. 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.
Associations.
The table contains information that associates files with specific extensions to particular applications. This is essentially the same function performed by the [extensions] section of the WIN.INI.
Shell Operations.
Windows contains two programs that are refered to as Shell programs. The term Shell refers to a program that organizes basic operating system tasks, like running applications, opening files, and sending files to the printer. Shell programs use list, windows, menus, and dialog boxes to perform these operations. In contrast, command systems like DOS require the entry of explicit command lines to accomplish these tasks
OLE Object Servers.
The registration database maintains a highly structured database of the details needed by programs that operate as object servers. This is by far the most complex task performed by the database. There is no WIN.INI equivalent for this function.
DDE/OLE Automation.
The registration database contains the details and the applications that support various types of DDE/OLE Automation operations.
It is useful to appreciate the difference in structure between the WIN.INI file and the REG.DAT database. WIN.INI is simply a text document. There are no special structures other than headings (simply titles enclosed in brackets) that organize the information. If you want to locate an item in the WIN.INI file, you must search through the file for the specific item you want to locate. The registration database is a tree-like, structured database used for storing information relating to program and file operations, in particular, those that involve the use of DDE or OLE. The tree structure makes it easier to keep the complex set of instructions, needed to implement DDE and OLE operations, organized and accessible by the applications that need to use them. This is not possible when you are working with a text document like WIN.INI. The WIN.INI file records all sorts or information about the Windows system in a simple sequential listing.