CHAPTER 1 INTRODUCTION

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CHAPTER 1 INTRODUCTION

• GOALS
• To understand the activity of programming
• To learn about the architecture of computers
• To learn about machine code and high level
  programming languages
• To become familiar with your computing
  environment and your compiler
• To compile and run your first Java program
• To recognize syntax and logic errors

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PREREQUISITES

• Computer savvy (file management, text editing)
• Problem solving skills
• Time management
• High school math (algebra, trigonometry)
• No prior programming background required

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What is a computer?

• Central processing unit
• Memory
• Peripherals
• Executes very simple instructions
• Executes instructions very rapidly
• General purpose device
• Programs describe specific actions

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Central Processing Unit (CPU)
5
Schematic Diagram of a Computer
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What Is A Program?

• Program a sequence of instructions that tell
  computer to perform a specific task
• Programming how to organize the sequence of
  instructions
• Programming language a set of conventions that
  represent the instructions
• Details of instruction description
• machine code
• assembler
• high-level

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Programming Languages

• Machine/Virtual Machine-- binary code 21 40 16
  100 163 240
• Assembleriload intRatebipush 100if_icmpgt
  intError
• High-level languageif (intRate gt 100) . . .
• Translating to machine code
• Machine code is the only code that computers can
  recognize
• Assembler and high-level languages must be
  translated to machine code
• Two ways for translation
• Interpretation
• Compilation

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The Java Programming Language

• A high-level language
• Simple
• Safe
• Platform-independent ("write once, run anywhere")
  
• Rich library
• Designed for the internet
• Object-oriented

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Applets on a Web Page
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Becoming Familiar with your Computer

• Login
• Locate the Java compiler
• Understand files and folders
• Write a simple program (later)
• Save your work
• Backup copies
• frequently save your file to disks

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A Shell Window
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An Integrated Development Environment
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File Hello.java

• 1 public class Hello
• 2
• 3 public static void main(String args)
• 4
• 5 // display a greeting in the console window
• 6 System.out.println("Hello, World!")
• 7
• 8

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A simple program

• public class ClassName
• public static void main(String args)
• // comment
• Method call object.methodName(parameters)
• System class
• System.out object
• println method

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Some Java Characteristics

• Case-sensitive
• Free-form layout
• A Java program must have one and only one method,
  called main, which is the program entrance
• Two ways for comments
• // -- comment a single line
• / ... / -- comment a paragraph
• Escape sequence \character
• Special characters that can not be displayed
  e.g. \n
• Specially used characters e.g. \
• Non-English letters e.g. è

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Syntax 1.1 Method Call

• Syntax
• object.methodName(parameters)
• class.methodName(parameters)
• Example
• System.out.println("Hello, Dave!")
• Purpose To invoke a method of an object and
  supply any additional parameters

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Compiling and Running

• Type program into text Editor
• Save to disk (hard or floppy disk)
• Open command shell
• Compile into byte codes -- Compiler javac
  Hello.java
• Execute byte codes -- Interpreterjava Hello

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From Source Code to Running Program
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Errors

• Syntax errors (or compile-time error)
• Detected by the compiler
• Examples
• Misspelling words System.ouch.print("...")
• Case-sensitive system.out.print("Hello)
• Missing something System.out.print( "Hello)
• Semantics error (or Logic errors or Run-time
  error )
• Detected (hopefully) through testing
• Examples
• System.out.print("Hell")

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The Edit-Compile-Test Loop