General Software Design Concepts( 3) · Virtua| Machines A module provides a virtual machine: a set of operations that can be invoked in a variety of ways and orders to accomplish a variety of tasks Don't think of systems in terms of components that correspond to steps in processing Do provide a set of virtual machines that are useful for writing many programs Information hiding Each design unit hides internal details of processing activities Design units communicate only through well-defined interfaces Each design unit specified by as little information as possible If internal details change, client units should need no changeCopyright Nancy Leveson, Sept. 1999 General Software Design Concepts (3) c Virtual Machines A module provides a virtual machine: a set of operations that can be invoked in a variety of ways and orders to accomplish a variety of tasks. Don’t think of systems in terms of components that correspond to steps in processing. Do provide a set of virtual machines that are useful for writing many programs. Information Hiding Each design unit hides internal details of processing activities. Design units communicate only through well-defined interfaces. Each design unit specified by as little information as possible If internal details change, client units should need no change �