Chapter 2: Replaceable Database Driver Architecture
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     CA-Clipper supports a driver architecture that allows CA-Clipper
     applications to use Replaceable Database Drivers (RDDs).  The RDD system
     makes CA-Clipper applications data-format independent.  Such
     applications can, therefore, access the data formats of other database
     systems, including the dBASE IV (.mdx), FoxPro (.cdx), and Paradox (.db)
     formats on a variety of equipment.  This driver architecture can even
     support database drivers that are not file-based, although all of the
     drivers supplied with CA-Clipper 5.2 are file-based.

     The concept of replaceable drivers is not new to this version of
     CA-Clipper.  In previous versions, the use of the default database
     driver (DBFNTX.LIB) was hidden by the fact that it was automatically
     linked into your application.  In fact, this is still the case.  The
     DBFNTX driver has been replaceable since it was first introduced in
     version 5.0.  Before this version, the DBFNTX driver was the only RDD
     supplied as part of the system.