Fall Semester, 2000
Introduction
© 2000, All Rights Reserved, SDSU & Roger Whitney
San Diego State University -- This page last updated 24-Aug-00
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CS 535 Object-Oriented Programming & Design Fall Semester, 2000 Introduction |
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© 2000, All Rights Reserved, SDSU & Roger Whitney San Diego State University -- This page last updated 24-Aug-00 |
Introduction
History and Languages
1967 Simula
1970 to 1983 Smalltalk developed
1979 Common LISP Object System
1980 Stroustrup starts on C++
1981 Byte Smalltalk issue
1983 Objective C
1986 C++
1987 Actor, Eiffel
1991 C++ release 3.0
199x Volumes of OO books/articles
1992 Refactoring thesis at UIUC
1995 Design Patterns, Squeak
1996 Java
1998 Extreme Programming
2000 Camp Smalltalk, C#
Other OO Languages
Self
Python
Perl 5
Prograph
Modula 3
Oberon
Scheme
Ruby
Smalltalk Venders
Cincom, IBM, Quasar, Disney
Prolog++
Ada 95
Object Pascal (Delphi)
Object X, X = Fortran, Cobol, etc.
Methodologies
Approach to developing software
Methodologies encompass
Goals of the Course
Learn how to program using classes and objects
Produce quality software
Quality and Development Time
The right end of the graph with high quality and high development time is found in projects like the Space Shuttle. The software on the shuttle has to work correctly all the time. One cannot reboot while the shuttle is in orbit. Most students and many(most?) companies are on the left side of the graph. They could reduce development by producing better software.
The University is not a Software Development Company
Faculty and Students
Meyer's Criteria for Evaluating for Modularity
Decomposability
Decompose problem into smaller subproblems
that can be solved separately
Example: Top-Down Design
Counter-example: Initialization Module
Meyer's Criteria for Evaluating for Modularity Composability
Freely combine modules to produce new systems
Examples: Math libraries
Unix command & pipes
Meyer's Criteria for Evaluating for Modularity Understandability
Individual modules understandable by human reader
Counter-example: Sequential Dependencies
Meyer's Criteria for Evaluating for Modularity Continuity
Small change in specification results in:
Changes in only a few modules
Does not affect the architecture
Example: Symbolic Constants
const MaxSize = 100
Meyer's Criteria for Evaluating for Modularity Protection
Effects of an abnormal run-time condition is confined to a few modules
Example: Validating input at source
Principles for Software Development
KISS Keep it simple, stupid
The simplest thing that could possible work
Supports:
Small is Beautiful See page 185 of Object-Oriented Software Development: A Practical Guide more information about these guidelines.
Upper bound for average size of an operation
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Code Size and Complexity
Applications of Principles
First program:
class HelloWorldExample { public static void main( String args[] ) { System.out.println( "Hello World" ); } }
Some Defintions
Abstraction
“Extracting the essential details about an item or group of items, while ignoring the unessential details.”
Edward Berard
“The process of identifying common patterns that have systematic variations; an abstraction represents the common pattern and provides a means for specifying which variation to use.”
Richard Gabriel
Example
Pattern: Priority queue Essential Details: length items in queue operations to add/remove/find item Variation: link list vs. array implementation stack, queue
Encapsulation
Enclosing all parts of an abstraction within a container
Information Hiding
Hiding parts of the abstraction
Coupling
Strength of interaction between objects in system
Cohesion
Degree to which the tasks performed by a single module are functionally related
Copyright ©, All rights reserved.
2000 SDSU & Roger Whitney, 5500 Campanile Drive, San Diego, CA 92182-7700 USA.
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