Transcript Week 1 - Intro to Object Oriented Programming

Week 1 - Introduction to ObjectOriented Programming
Outline
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
Machine Languages, Assembly Languages and High-Level
Languages
History of C++
History of Java
Java Class Libraries
Other High-Level Languages
Structured Programming
The Internet and the World Wide Web
Basics of a Typical Java Environment
Thinking About Objects: Introduction to Object Technology
and the Unified Modeling Language
 2002 Prentice Hall. All rights reserved.
1.1 Machine Languages, Assembly
Languages and High-Level Languages
• Machine language
– “Natural language” of computer component
– Machine dependent
• Assembly language
– English-like abbreviations represent computer operations
– Translator programs convert to machine language
• High-level language
– Allows for writing more “English-like” instructions
• Contains commonly used mathematical operations
– Compiler convert to machine language
• Interpreter
– Execute high-level language programs without compilation
 2002 Prentice Hall. All rights reserved.
1.2
History of C++
• C++
– Evolved from C
• Evolved from BCPL and B
– Provides object-oriented programming capabilities
• Objects
– Reusable software components that model real-world items
 2002 Prentice Hall. All rights reserved.
1.3
History of Java
• Java
– Originally for intelligent consumer-electronic devices
– Then used for creating Web pages with dynamic content
– Now also used for:
• Develop large-scale enterprise applications
• Enhance WWW server functionality
• Provide applications for consumer devices (cell phones, etc.)
 2002 Prentice Hall. All rights reserved.
1.4
Java Class Libraries
• Classes
– Contain methods that perform tasks
• Return information after task completion
– Used to build Java programs
• Java contains class libraries
– Known as Java APIs (Application Programming Interfaces)
 2002 Prentice Hall. All rights reserved.
1.5 Other High-Level Languages
• Fortran
– FORmula TRANslator
• COBOL
– COmmon Business Oriented Language
• Pascal
• Basic
 2002 Prentice Hall. All rights reserved.
1.6 Structured Programming
• Structured Programming
– Structured programs
• Clearer than unstructured programs
• Easier to test, debug and modify
– Pascal designed for teaching structured programming
– ADA
• Multitasking
– C
 2002 Prentice Hall. All rights reserved.
1.7 The Internet and the World Wide Web
• Internet
– Developed over three decades ago with DOD funding
– Originally for connecting few main computer systems
– Now accessible by hundreds of millions of computers
• World Wide Web (WWW)
– Allows for locating/viewing multimedia-based documents
 2002 Prentice Hall. All rights reserved.
1.8 Basics of a Typical Java Environment
• Java systems contain
–
–
–
–
Environment
Language
APIs
Class libraries
 2002 Prentice Hall. All rights reserved.
1.8 Basics of a Typical Java Environment
(cont.)
• Java programs normally undergo five phases
– Edit
• Programmer writes program (and stores program on disk)
– Compile
• Compiler creates bytecodes from program
– Load
• Class loader stores bytecodes in memory
– Verify
• Verifier ensures bytecodes do not violate security requirements
– Execute
• Interpreter translates bytecodes into machine language
 2002 Prentice Hall. All rights reserved.
Fig. 1.1 A typical Java environment.
Pha se 1
Pha se 2
Edit or
Com piler
Disk
Disk
Prog ram is c reat ed in
the edit or and sto red
on d isk.
Com piler c rea te s
byt ec odes and st ores
the m on disk.
Prim ary
Mem ory
Pha se 3
Class Lo ad er
Class loa de r p ut s
byt ec o des in m em ory.
Disk
.
.
.
.
.
.
Prim ary
Mem ory
Pha se 4
Byt ec ode Ve rifier
.
.
.
.
.
.
Prim ary
Mem ory
Pha se 5
Int erp ret er
.
.
.
.
.
.
 2002 Prentice Hall. All rights reserved.
By te c ode verif ier
c onf irms t hat a ll
byt ec odes are v alid
and do not violat e
Java ’ s sec urit y
rest ric t ions.
Int erpret er read s
byt ec odes and
translat es them into a
la nguag e t hat t he
c om put er c an
und ersta nd, possib ly
st oring d at a values a s
the program exec ut es.
1.9 Thinking About Objects: Introduction to
Object Technology and the Unified Modeling
Language
• Object orientation
• Unified Modeling Language (UML)
– Graphical language that uses common notation
– Allows developers to represent object-oriented designs
 2002 Prentice Hall. All rights reserved.
1.12 Thinking About Objects (cont.)
• Objects
– Reusable software components that model real-world items
– Look all around you
• People, animals, plants, cars, etc.
– Attributes
• Size, shape, color, weight, etc.
– Behaviors
• Babies cry, crawl, sleep, etc.
 2002 Prentice Hall. All rights reserved.
1.13 Thinking About Objects (cont.)
• Object-oriented design (OOD)
– Models real-world objects
– Models communication among objects
– Encapsulates data (attributes) and functions (behaviors)
• Information hiding
• Communication through well-defined interfaces
• Object-oriented language
– Programming is called object-oriented programming (OOP)
– Java
 2002 Prentice Hall. All rights reserved.
1.14 Thinking About Objects (cont.)
• Object-Oriented Analysis and Design (OOAD)
– Essential for large programs
– Analyze program requirements, then develop solution
– We begin OOAD in Chapter 2
• Elevator-simulation case study
 2002 Prentice Hall. All rights reserved.
1.15 Thinking About Objects (cont.)
• History of the UML
–
–
–
–
Need developed for process with which to approach OOAD
Brainchild of Booch, Rumbaugh and Jacobson
Object Management Group (OMG) supervised
Version 1.4 is current version
• Version 2.0 scheduled tentatively for release in 2002
 2002 Prentice Hall. All rights reserved.
1.16 Thinking About Objects (cont.)
• UML
– Graphical representation scheme
– Enables developers to model object-oriented systems
– Flexible and extendible
 2002 Prentice Hall. All rights reserved.