Modularization

A program can be very long and complex. To manage such a complexity, it is necessary to realize programs in a modular way.

• The program must be structured in autonomous parts, called modules.
• The various modules are related to each other through precise relations.

A module is characterized by:

• services exported to clients (these are other modules that make use of such services)
• an interface, i.e., the way in which such services are exported
• imported services, i.e., services for which the module is a client
• an internal structure, i.e., how the module is realized; the internal structure is not of interest for clients.

The use of modularization allows us to realize programs as follows:

1. we define which modules are necessary to solve the requested problem;
2. we define how these modules are related to each other;
3. we develop each module independently from the other modules.

By proceeding in this way we enhance various qualities of a program, which simplify dealing with the program. Specifically:

• readability (or understandability) of the program
• extensibility (i.e., the possibility of extending the functionalities of the program, if necessary)
• reusability of parts of the program for different purposes