Program Segmentation using Include Directives

When your code base becomes very large, dividing it into smaller sections can greatly aid in code maintenance. The %include directive is designed for this purpose. It tells the compiler to insert the contents of another file at that point in the program.

The %include directive supports two optional modifiers:

• continue — Tells the compiler to proceed even if the include file is missing or cannot be opened. This enables conditional inclusion of platform-specific or optional modules.
• once — Ensures that the file is included only once, even if referenced multiple times (directly or indirectly). This avoids duplicate declarations during nested includes.

Include files can also be nested—an include file can itself contain additional %include directives. This allows you to create reusable, modular layers of code for better organization.

Simple Include Example

Suppose we have a file named safe_common.spinc that defines some shared data and a utility routine:

You can include this file in your main program like this:

Large business applications can easily contain hundreds of thousands of lines of code. These applications are greatly simplified by using many include directives. Typically, each include file contains all the variables and routines needed to perform a specific subtask.

Example: Nested Includes with once

The following example demonstrates how include files can reference other include files. We use the once modifier to ensure that files are not included more than once, even when nested.

When main.spsrc is compiled, it automatically brings in both common.inc and logging.inc. Thanks to once, even if logging.inc is included from multiple files, it is compiled only once.