f90SQL adds an additional layer to the ODBC architecture represented in Figure 2.1. This new layer makes it easier for Fortran applications to access the ODBC-API. Figure 2.2 shows the new scheme.
Figure 2.2. Relationship among the four components of ODBC and f90SQL.
Note that f90SQL is not a replacement of the ODBC-API. It just acts as an interface between your Fortran application and the functions in the API. You Fortran applications call subroutines in f90SQL. These subroutines take care of checking passed parameters, reformatting data, and other details before calling the necessary functions in the ODBC-API. If the called ODBC-API functions return data, then f90SQL makes sure these data are formatted in an amenable way to be further processed by your Fortran application. With this scheme, many of the complications of calling the ODBC-API from Fortran are eliminated.
It is important to note that, because most subroutines in f90SQL are only an interface to the original ODBC functions, they will behave in a similar manner. This means they are also subject to the same limitations and calling sequence of the ODBC-API.