Modularity and Information Hiding in Program Design

Check out pages 145 to 146 in the book.

Jan 27, 2000

Procedural Abstraction

• When you organize a sequence of instructions into a named procedure to perform an action.

Abstraction

• Separate the what from the how
  • Ease of use
  • Ease of modification

Abstract Data Types

• Isolate the data structure from its use.
• Key component in large scale software development.

Why data abstraction?

• Creating data should be separate from using data
• Users don't need to know details of data definition and manipulation
• Users only need to know what they can do to the data

What is an ADT?

• Definition of a data structure reflecting a real-world model.
• Definition of the operations allowed on that data structure such as:
  • Ability to read and write the data structure as an operation
  • Other operations may or may not be needed.

ADT operations.

• Defined as procedures or functions
• Must use parameters for all data passing
• User knows operation name and required arguments.

Information Hiding

• Ease of use
• Ease of modification

Encapsulation

• Keeps related content together
• Separates certain specified requirements from other parts of the specification which may use those requirements.

Encapsulation from the terminology point of view

• this "capsule" object is usually called a Class.
• The functions inside the class are called private methods
• The data inside the class are private variables
• The interface functions for the outside world to your private methods are public methods.
• You can also have public variables (The use of public variables is often considered to be a bad habit).

Modularity

• Packages
• Import Statements
• Custom made classes/packages