INF Back-Link Functionality in Visual FoxPro for Windows

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A Visual FoxPro table (.DBF) that is stored in a database (DBC) holds a reference to the database that contains it. This information is referred to as back-link. A back-link allows opening or selecting a table in a database without explicitly referring to the DBC. It provides a way to access the rules and triggers associated with a table.

Back-link information is recorded in the .DBF header and contains the relative path and file name that link the table to the database. Two hundred and sixty three bytes (263) have been added to the .DBF header to accommodate back-link functionality. Any table created with Visual FoxPro will have to be modified to be used with FoxPro versions 2.x for Windows, FoxPro versions 2.x for MS-DOS, or FoxBASE+.

You can convert a Visual FoxPro table to the FoxPro version 2.x structure by using the COPY TO command. For example:

   USE SAMPLES\DATA\CUSTOMER
   COPY TO CUSTBAK1 TYPE FOX2x && Copies to a FoxPro 2.x compatible format
   COPY TO CUSTBAK2 TYPE FOXPLUS && Copies to a FoxBASE+ compatible format

				

A FoxPro version 2.x for Windows or FoxPro version 2.x for MS-DOS table is converted to the Visual FoxPro format when it is added to a database, or when its structure is changed to use NULLs or a data type introduced in Visual FoxPro. When the conversion occurs, a backup (.BAK) file is created.