Converting FPW 2.6 data

Converting the data is the very simplest part of the process because Visual FoxPro can work natively with data files in FoxPro 2.6 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 2.6 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.xx 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 do not need to be upgraded, VFP can read and write to files which it shares with FPW. 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 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.

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