> In foxpro 2.5, it opens the dbf and cdx file fine and works very well.
>today, we want to use visual foxpro 3.0 to update the application system.
>we open the dbf file fine but when I use 'set order to tag key1_tag' it
>cause an error 'Variable 'key1_tag' is not found''. I don't
>know what happened.

Let's see -- what happens if you try to modify the table's structure in VFP3? It should show you the index tags. If it doesn't, try opening the table in 2.5 and COPY TO newFile CDX. Then, try opening newFile in 3.0. If that works, just trash the old file and rename newFile.dbf and newFile.cdx (and .fpt?)

> I create a dbf file in vfp 3.0 and try to open it in foxpro 2.5,but it
>can't be open! this must have some relations to my current problem.

Right -- as was pointed out, the 3.0 file structure is different from the 2.5. However, 2.5 files should work just fine in 3.0. To make a 3.0 dbf work in 2.5, you need to COPY TO newFile TYPE FOX2X -- that strips the database container information from the copy of the table.

> In C language file, it is only a system function to create the dbf and cdx
>file. I think it is difficult to modify the C language file. What can I do?

Don't worry about it, basically. :-)