Converting FoxPro 2 data
Converting the data is the very simplest part of the process because
Visual FoxPro can work natively with data files in FoxPro 2 format.
The system of storing fixed-length data in a .dbf file, variable length
data such as memo fields and graphics in a .fpt file, and the indexes
in a .cdx file has remained the same.
The big difference in data storage between FoxPro 2 and Visual FoxPro is
the concept of the database container. All VFP data files can take
advantage of features provided by the database container such as long
field names, validation and referential integrity. In order to be able
to do this, each dbf file has an area in its header which stores a
reference to that file's database container. Files from version 2 lack
this entry and these versions of FoxPro do not recognise a VFP-format dbf
file at all. This is scarcely surprising. The writers of FoxPro 2.00 could
not be expected to predict the changes that would be made in the next ten
years.
The writers of VFP on the other hand were able to give Visual FoxPro the
ability to read and write the older version of the files. The table
structures from your existing database do not need to be upgraded, VFP
can read and write to files in the old format. Both versions even respect
each other's record locks so you can have users of both generations of
FoxPro working with the same files simultaneously.
Practical aspects
This ability to share data makes the practical work of converting very
much easier. If necessary, the old and new versions of the software can
run in parallel during testing and direct comparisons can be made between
them. The new software can even be introduced into production use stage by
stage.
Introduction
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