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Carrano : Chapter 1. Software Engineering and Object-Oriented Design Topics: Solutions Modules Key Programming Issues Development Methods Object-Oriented Principles. What is a Good Solution?. A solution is good if: The total cost it incurs over all phases of its life cycle is minimal

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carrano chapter 1
Carrano: Chapter 1

Software Engineering and Object-Oriented Design

  • Topics:
    • Solutions
    • Modules
    • Key Programming Issues
    • Development Methods
    • Object-Oriented Principles
what is a good solution
What is a Good Solution?
  • A solution is good if:
    • The total cost it incurs over all phases of its life cycle is minimal
  • The cost of a solution includes:
    • Computer resources that the program consumes
    • Difficulties encountered by users
    • Consequences of a program that does not behave correctly
  • Programs must be well structured and documented
  • Efficiency is one aspect of a solution’s cost
what is a module
What is a Module?
  • A Module is a part of a program that accomplishes a task.
  • In procedural programming, Modules are made up of one or more functions.
  • Large Modules may contain Sub-Modules.
structure of a module
Structure of a Module
  • Modules have two primary components: an Interface and Internal Components.
    • In procedural programming, a module’s interface is just header of the function that you call to start the module.
    • Internal Components are the sub-modules/functions that do the task the module is designed to do.
how to evaluate a module
How to Evaluate a Module
  • Cohesion
    • A highly cohesive module performs one well-defined task
    • Leads to modular solutions
    • Reduces Coupling
  • Coupling
    • Modules with low coupling are independent of one another
    • Modules shouldn’t affect other modules when changed.
    • Low coupling increases Cohesion.
seven key issues in programming
Seven Key Issues in Programming
  • Modularity
  • Style
  • Modifiability
  • Ease of Use
  • Fail-safe programming
  • Debugging
  • Testing
1 modularity
1) Modularity
  • Modularity has a favorable impact on
    • Constructing programs
    • Debugging programs
    • Reading programs
    • Modifying programs
    • Eliminating redundant code
    • Reuse of code
2 style
2) Style

Programming Style can enhance code with:

  • Use of private data members
  • Proper use of reference arguments
  • Proper use of functions
  • Avoidance of global variables in modules
  • Error handling
  • Readability
  • Documentation
3 modifiability
3) Modifiability
  • Modifiability is easier through the use of
    • Named constants
    • The typedefstatement
4 ease of use
4) Ease of Use
  • The easier a program is to use, the more impressed users will be with it.
    • In an interactive environment, the program should prompt the user for input in a clear manner
    • A program should always echo its input
    • The output should be well labeled and easy to read
5 fail safe programming
5) Fail-Safe Programming
  • Fail-safe programs will perform reasonably no matter how anyone uses them
    • Test for invalid input data and program logic errors
    • Check invariants
    • Enforce preconditions
    • Check argument values
6 debugging
6) Debugging
  • Programmers must systematically check a program’s logic to find and correct errors
  • Tools to use while debugging:

– Single-stepping

– Watches

– Breakpoints

– cout statements

– Dump functions

7 testing
7) Testing
  • Levels
    • Unit testing: Test functions, then modules
    • Integration testing: Test interactions among modules
    • System testing: Test entire program
    • Acceptance testing: Show that system complies with requirements
development methods waterfall
Development Methods, Waterfall
  • One simple but somewhat outdated method is the Waterfall Method.
  • Though it can be used modularly, this design method requires each preceding stage to be complete before progressing to the next stage. In practice, this leads to inflexibility and a constant state of incompleteness.
development methods iterative
Development Methods, Iterative
  • Newer methods are iterative.
    • Many short, fixed-length iterations
    • Each iteration builds on the previous iteration until a complete solution is achieved
    • Each iteration cycles through analysis, design, implementation, testing, and integration of a small portion of the problem domain
    • Early iterations create the core of the system; further iterations build on that core
development methods iterative1
Development Methods, Iterative
  • Features of Iterative methods:
    • The partial system at the end of each iteration should be functional and completely tested
    • Each iteration makes relatively few changes to the previous iteration
    • End users can provide feedback at the end of each iteration

One specific iterative method is the Rational Unified Process (RUP)

object oriented programming
Object-Oriented Programming
  • The most modern approach to designing modules is the Object-Oriented approach.
    • Instead of creating groups of functions, create classes.
    • Classes are combinations of data sets and methods (functions that operate on the data set)
    • Classes are combined and caused to interact to create solutions.
principles of object oriented programming oop
Principles of Object-Oriented Programming (OOP)
  • Object-oriented languages enable us to build classes that can be used to instantiate (create) objects
  • A class combines
    • Attributes (characteristics) of objects of a single type
      • Typically data
      • Called data members
    • Behaviors (operations)
      • Typically operate on the data
      • Called methods or member functions
  • An object is an instance of a class.

Class:

Objects:

principles of object oriented programming
Principles of Object-Oriented Programming
  • Three principles of object-oriented programming
    • Encapsulation
      • Objects combine data and operations
      • Hides inner details
    • Inheritance
      • Classes can inherit properties from other classes
      • Existing classes can be reused
    • Polymorphism
      • Objects can determine appropriate operations at execution time
object oriented analysis and design
Object-Oriented Analysis and Design
  • Object-Oriented Analysis (OOA)
    • Coming up with the classes that can be used to define the problem.
    • Emphasis on what a solution must do.
  • Object-Oriented Design (OOD)
    • Understanding how the classes can interact and what they can do alone or together.
applying the uml to ooa d
Applying the UML to OOA/D
  • UML (Unified Modeling Language) is very often used in OOA/D to define classes and their interactions.

A UML class definition:

A UML interaction diagram:

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