4. Subsystems

All work the system performs is done in subsystems. Think of a subsystem as a department in your company. Employees belong to one department or another. Each department specializes in some kind of work, such as sales, accounting, marketing, production, or shipping. By the same token, subsystems are also specialized. There is, however, one general-purpose subsystem, called QBASE.

You can run your system using QBASE to do all the work, or you can split the work among several subsystems. IBM ships the i5 with the QBASE option.