The Preprocessor and Program Development

Pascal ALLBASE/SQL application programs originate as Pascal source files that are subsequently compiled with the Pascal compiler and linked by the 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 Pascal ALLBASE/SQL Program”, the ALLBASE/SQL Pascal program consists of one source file and, optionally, one or more include files. The preprocessor merges any user include file into the source program, and preprocesses it. The result is a modified source code file and several preprocessor-generated include files. These preprocessor include files contain all of the definitions of variables used by any Pascal statements in the modified source code file. These two files are then compiled to produce an object code file, and linked to produce an executable program file, in the same manner as any other Pascal program.

Figure 2-1 Developing a Pascal ALLBASE/SQL Program

In other cases, the ALLBASE/SQL application program might consist of a main program and one or more subprograms in separate files. In these cases, only source files containing SQL commands need to be preprocessed, as illustrated in Figure 2-2 “Developing a Pascal ALLBASE/SQL Program with Subprograms”. You invoke the Pascal compiler as many times as necessary to create the desired number of object code files. The files output by the Pascal preprocessor are treated just as any other compiler input files at compile time.

	NOTE: 300/400 Series 300 and 400 systems do not allow subprograms. The parts of Figure 2-2 “Developing a Pascal ALLBASE/SQL Program with Subprograms” shown with diagonal lines do not apply to Series 300 and 400 systems.

Figure 2-2 Developing a Pascal ALLBASE/SQL Program with Subprograms

During preprocessing, the Pascal preprocessor actually accesses one of the DBEnvironments to be used by your program at run time. It can be the same DBEnvironment your program uses at run time, or a DBEnvironment into which your program is installed. The preprocessor stores a module in the DBEnvironment which is executed at run time. The module is used at run time to optimize and validate DBEnvironment operations.

During any invocation, the Pascal preprocessor can access only one DBEnvironment. You can create separate subprograms that all access the same DBEnvironment. Each program is separately preprocessed and compiled. In this case, the preprocessor stores multiple modules in one DBEnvironment.

The criteria governing the division of an application program into subprograms 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 Pascal application programs, the only additional factors are as follows: