The Preprocessor and Program Development

ALLBASE/SQL FORTRAN application programs have the same stages of development as any application program. They originate as FORTRAN source code files that are subsequently compiled with the FORTRAN compiler and linked by the system linker to create an executable program file. The development of ALLBASE/SQL programs, however, requires that you preprocess those portions of the program that contain SQL commands before compilation.

In the case illustrated in Figure 2-1 “Developing a FORTRAN Program”, the ALLBASE/SQL FORTRAN program consists of one source file and one user include file. The preprocessor merges any user include file into the source program, and preprocesses it. The result is a modified source code file and a preprocessor generated include file. This preprocessor include file contains all of the definitions of variables used by any FORTRAN statements in the modified source code file. These two files are then compiled to produce an object code module, and linked to produce an executable program file, in the same manner as any other FORTRAN program.

Figure 2-1 Developing a FORTRAN Program

In other cases, the ALLBASE/SQL application program might consist of a main program unit and one or more subprogram units in separate files. In these cases, only source files containing embedded SQL code need to be preprocessed, as illustrated in Figure 2-2 “Developing a FORTRAN Program with Subprograms”. However, each program unit which contains SQL commands must be preprocessed and compiled before the next program unit is preprocessed. Separately preprocessed program units that are not immediately compiled will write over each other's preprocessor created include file and consequently create an error when compiled. You invoke the FORTRAN preprocessor and compiler as many times as necessary to create the desired number of object code modules. The files output by the FORTRAN preprocessor are treated just as any other compiler input files at compile time.

Figure 2-2 Developing a FORTRAN Program with Subprograms

During preprocessing, the FORTRAN preprocessor actually accesses the same DBEnvironment to be used by your main program or subprogram unit at runtime. The preprocessor stores a module in the DBEnvironment which is executed at runtime. The module is used at runtime to optimize and validate DBEnvironment operations.

During any invocation, the FORTRAN preprocessor can access only one DBEnvironment. Therefore programs that access multiple DBEnvironments must be divided into multiple subprogram units, each of which accesses only one DBEnvironment. Program units that access the same DBEnvironment may be preprocessed and compiled separately or jointly. The preprocessor stores a module in each DBEnvironment accessed for each preprocessor invocation.

You can also create separate subprogram units that all access the same DBEnvironment. Each subprogram stores multiple modules in one DBEnvironment. Each module consists of sections with each section representing one SQL command.

The criteria governing the division of an application program into subprogram units is very application-dependent. As in the development of any application program, factors such as program size, program complexity, expected recompilation frequency, and number of programmers affect how a program is subdivided. In the case of ALLBASE/SQL FORTRAN application programs, the only additional factors are: