1.  2003 Prentice Hall, Inc. All rights reserved. 1 Chapter 1 – Introduction to Computers, the Internet, and the Web Outline 1.1 Introduction 1.2 What Is a Computer? 1.3 Computer Organization 1.4 Evolution of Operating Systems 1.5 Personal, Distributed and Client/Server Computing 1.6 Machine Languages, Assembly Languages and High-Level Languages 1.7 History of C++ 1.8 History of Java 1.9 Java Class Libraries 1.10 FORTRAN, COBOL, Pascal and Ada 1.11 BASIC, Visual Basic, Visual C++, C# and.NET 1.12 The Internet and the World Wide Web 1.13 Basics of a Typical Java Environment

2.  2003 Prentice Hall, Inc. All rights reserved. 2 Chapter 1 – Introduction to Computers, the Internet, and the Web 1.14 General Notes about Java and This Book 1.15 Thinking About Objects: Introduction to Object Technology and the Unified Modeling Language 1.16 Discovering Design Patterns: Introduction

3.  2003 Prentice Hall, Inc. All rights reserved. 3 1.1 Introduction Java How to Program, Fifth Edition –Java 2 Standard Edition Other Editions: J2EE, J2ME –Object-oriented programming Internal structure of objects often is built using structured programming

4.  2003 Prentice Hall, Inc. All rights reserved. 4 1.2 What Is a Computer? Computer –Performs computations and makes logical decisions –Millions / billions times faster than human beings Computer programs –Sets of instructions for which computer processes data Hardware –Physical devices of computer system Software –Programs that run on computers

5.  2003 Prentice Hall, Inc. All rights reserved. 5 1.3 Computer Organization Six logical units of computer system –Input unit Mouse, keyboard –Output unit Printer, monitor, audio speakers –Memory unit Retains input and processed information –Arithmetic and logic unit (ALU) Performs calculations –Central processing unit (CPU) Supervises operation of other devices –Secondary storage unit Hard drives, floppy drives

6.  2003 Prentice Hall, Inc. All rights reserved. 6 1.4 Evolution of Operating Systems Batch processing –One job (task) at a time –Operating systems developed Programs to make computers more convenient to use Switch jobs easier Multiprogramming –“Simultaneous” jobs –Timesharing operating systems –Multithreads ( 多重執行緒 )

7.  2003 Prentice Hall, Inc. All rights reserved. 7 1.5 Personal, Distributed and Client/Server Computing Personal computing –Computers for personal use Distributed computing –Computing performed among several computers Client/server computing –Servers offer common store of programs and data –Clients access programs and data from server Three-Tier computing –Browser, Web server, Database server

8.  2003 Prentice Hall, Inc. All rights reserved. 8 1.6 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

9.  2003 Prentice Hall, Inc. All rights reserved. 9 1.7 History of C++ C++ –Evolved from C Evolved from BCPL and B –Provides object-oriented programming capabilities Objects –Reusable software components that model pieces of software programs in terms of properties and behaviors. Question: –What are the good and bad parts of C++

10.  2003 Prentice Hall, Inc. All rights reserved. 10 1.8 History of Java Java –Originally for intelligent consumer-electronic devices –Then used for creating Web pages with dynamic content –SUN formally announced Java in May 1995 –Now also used for: Develop large-scale enterprise applications [J2EE, RMI, CORBA] Enhance WWW server functionality [JSP, Servlet, Web Services, JavaScript] Provide applications for consumer devices (cell phones, etc.) [J2ME]

11.  2003 Prentice Hall, Inc. All rights reserved. 11 1.9 Java Class Libraries Classes –Include 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) –Reference: http://java.sun.com/j2se/1.4.1/docs/api/

12.  2003 Prentice Hall, Inc. All rights reserved. 12 1.10 FORTRAN, COBOL, Pascal and Ada Fortran –FORmula TRANslator COBOL –COmmon Business Oriented Language Pascal –Structured programming Ada –Multitasking

13.  2003 Prentice Hall, Inc. All rights reserved. 13 1.11 BASIC, Visual Basic, Visual C++, C# and.NET BASIC –Beginner’s All-Purpose Symbolic Instruction Code Visual Basic.NET –Framework Class Library (FLC) Visual C++ –Microsoft Foundation Classes (MFC) C# –C-Sharp.NET –.NET platform

14.  2003 Prentice Hall, Inc. All rights reserved. 14 1.12 The Internet and the World Wide Web Internet –Developed more than four decades ago with DOD funding TCP/IP, telnet, etc. –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

15.  2003 Prentice Hall, Inc. All rights reserved. 15 1.13 Basics of a Typical Java Environment 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

16.  2003 Prentice Hall, Inc. All rights reserved. 16 Fig. 1.1 Typical Java environment. Primary Memory............ Disk Editor Compiler Class Loader Program is created in an editor and stored on disk in a file ending with.java. Compiler creates bytecodes and stores them on disk in a file ending with.class. Class loader reads.class files containing bytecodes from disk and puts those bytecodes in memory. Phase 1 Phase 2 Phase 3 Primary Memory............ Bytecode Verifier Bytecode verifier confirms that all bytecodes are valid and do not violate Java’s security restrictions. Phase 4 Primary Memory............ Interpreter Interpreter reads bytecodes and translates them into a language that the computer can understand, possibly storing data values as the program executes. Phase 5

17.  2003 Prentice Hall, Inc. All rights reserved. 17 1.14 General Notes about Java and This Book Geared for novice and experienced programmers Reference: –http://java.sun.comhttp://java.sun.com –http://www.deitel.comhttp://www.deitel.com –http://www.prenhall.com/deitelhttp://www.prenhall.com/deitel

18.  2003 Prentice Hall, Inc. All rights reserved. 18 1.15 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

19.  2003 Prentice Hall, Inc. All rights reserved. 19 1.15 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.

20.  2003 Prentice Hall, Inc. All rights reserved. 20 1.15 Thinking About Objects (cont.) Object-oriented design (OOD) –Models real-world objects –Models communication among objects –Encapsulates ( 原意 : 封入膠囊 ) attributes and operations (behaviors) Information hiding Communication through well-defined interfaces Object-oriented language –Programming in object oriented languages is called object- oriented programming (OOP) –Java programmers concentrate on creating classes and interfaces –Groups of related classes are often packaged as reusable components

21.  2003 Prentice Hall, Inc. All rights reserved. 21 1.15 Thinking About Objects (cont.) Object-Oriented Analysis and Design (OOA/D) –Essential for large programs –Analyze program requirements, then develop solution –UML Unified Modeling Language

22.  2003 Prentice Hall, Inc. All rights reserved. 22 1.15 Thinking About Objects (cont.) History of the UML –Need developed for process with which to approach OOA/D –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 2003

23.  2003 Prentice Hall, Inc. All rights reserved. 23 1.15 Thinking About Objects (cont.) UML –Graphical representation scheme –Enables developers to model object-oriented systems –Flexible and extendible Reference: –http://www.omg.orghttp://www.omg.org –http://www.rational.com/uml/index.jsp

24.  2003 Prentice Hall, Inc. All rights reserved. 24 1.16 Discovering Design Patterns: Introduction Effective design crucial for large programs Design patterns –Proven architectures for developing object-oriented software Architectures created from accumulated industry experience –Reduce design-process complexity –Promotes design reuse in future systems –Helps identify common design mistakes and pitfalls –Helps design independently of implementation language –Establishes common design “vocabulary” –Shortens design phase in software-development process

25.  2003 Prentice Hall, Inc. All rights reserved. 25 1.16 Discovering Design Patterns (cont.) Design patterns –Similar to architectural elements arches and columns –Used by developers to construct sets of classes and objects Developers –Familiarity with patterns to understand how to use patterns

26.  2003 Prentice Hall, Inc. All rights reserved. 26 1.16 Discovering Design Patterns (cont.) History of Design Patterns –Gamma, Helm, Johnson and Vlissides “Gang of Four” Design Patterns, Elements of Reusable Object-Oriented Software (Addison Wesley: 1995) Established 23 design patterns –Creational Instantiate objects –Structural Organize classes and objects –Behavioral Assign responsibilities to objects