Introduction to Computers, the Internet and the Web
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This chapter introduces key concepts related to computers, programming languages, and Java. It describes the basic parts of a computer and how they work together. It outlines the evolution of operating systems and different models of computing. It also discusses the history and characteristics of various programming languages like Java, C++, and FORTRAN. Additionally, it introduces object-oriented programming concepts like classes, objects, and design patterns. Finally, it provides an overview of the structure of a typical Java development environment.
Introduction to Computers, the Internet and the Web
- 1. © 2003 Prentice Hall, Inc. All rights reserved. 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. 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. 1.1 Introduction • Java How to Program, Fifth Edition – Java 2 Standard Edition – Object-oriented programming
- 4. © 2003 Prentice Hall, Inc. All rights reserved. 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. 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. 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
- 7. © 2003 Prentice Hall, Inc. All rights reserved. 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
- 8. © 2003 Prentice Hall, Inc. All rights reserved. 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. 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 real-world items
- 10. © 2003 Prentice Hall, Inc. All rights reserved. 1.8 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.)
- 11. © 2003 Prentice Hall, Inc. All rights reserved. 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)
- 12. © 2003 Prentice Hall, Inc. All rights reserved. 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. 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. 1.12 The Internet and the World Wide Web • Internet – Developed more than four 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
- 15. © 2003 Prentice Hall, Inc. All rights reserved. 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. Fig. 1.1 Typical Java environment. Primary Memory . . . . . . Disk Disk 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. 1.14 General Notes about Java and This Book • Geared for novice programmers • We stress clarity
- 18. © 2003 Prentice Hall, Inc. All rights reserved. 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. 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. 1.15 Thinking About Objects (cont.) • Object-oriented design (OOD) – Models real-world objects – Models communication among objects – Encapsulates 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
- 21. © 2003 Prentice Hall, Inc. All rights reserved. 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. 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. 1.15 Thinking About Objects (cont.) • UML – Graphical representation scheme – Enables developers to model object-oriented systems – Flexible and extendible
- 24. © 2003 Prentice Hall, Inc. All rights reserved. 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. 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. 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