4.0 Chapter Goals

The purpose of this chapter is to elaborate on the composition abstraction for collecting sections of code under a single name. When the code in question is needed in the main program, only its name need be written. In Modula-2, composition is achieved by using the procedure mechanism, the code for which is placed in the declaration part of a module, and that can be used freely throughout the main program. On completing the chapter, the student should understand and be able to use the following:

Data Representation Abstractions

General:

Procedures as data types

Realized in the Modula-2 notation:

procedure types

Data Manipulation Abstractions

General:

code encapsulation, input and output parameters

Realized in the Modula-2 notation:

procedure value and variable parameters; formal and actual parameters

Programming Abstractions

General:

Top-down design and planning is extended to breaking a problem into sub-tasks that are then encapsulated as separate sections of code and called upon as desired.

Realized in the Modula-2 notation:

procedures, function procedures, recursion


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