A subsystem is a coherent part of the complete system to be built. It is represented by a set of sources and one single object directory. A system can be composed of a single subsystem when it is simple as we have seen in the first section. Complex systems are usually composed of several interdependent subsystems. A subsystem is dependent on another subsystem if knowledge of the other one is required to build it, and in particular if visibility on some of the sources of this other subsystem is required. Each subsystem is usually represented by its own project file.
In this section, the previous example is being extended. Let's assume some
sources of our Build project depend on other sources.
For instance, when building a graphical interface, it is usual to depend upon
a graphical library toolkit such as GtkAda. Furthermore, we also need
sources from a logging module we had previously written.