If VFP9 can recognize long data type name than it's used. Otherwise the first letter of the data type is used for backward compatibility. You can find the list of data types in the CREATE TABLE - SQL Command help topic.

>VFP9 let users to use long field type names at creating tables with code.
>run and look:
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>CREATE TABLE sample ( sfield doub )
>modi stru
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>If you use that there is not any problem:
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>CREATE TABLE sample ( sfield double )
>