Transcript CHAPTER 1

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
PREREQUISITES
• Computer savvy (file management, text
editing)
 Problem solving skills
 Time management
 High school math (algebra, trigonometry)
 No prior programming background
required
What is a computer?
 Central processing unit
 Memory
 Peripherals
 Executes very simple instructions
 Executes instructions very rapidly
 General purpose device
 Programs describe specific actions
Central Processing Unit (CPU)
Schematic Diagram of a Computer
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
Programming Languages
 Machine/Virtual Machine
-- binary code: 21 40 16 100 163 240
 Assembler
iload intRate
bipush 100
if_icmpgt intError
 High-level language
if (intRate > 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
The Java Programming Language
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A high-level language
Simple
Safe
Platform-independent ("write once, run
anywhere")
 Rich library
 Designed for the internet
 Object-oriented
Applets on a Web Page
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
A Shell Window
An Integrated Development Environment
File Hello.java
1 public class Hello
2{
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public static void main(String[] args)
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{
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// display a greeting in the console window
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System.out.println("Hello, World!");
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8}
}
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
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
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
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 -- Interpreter
java Hello
From Source Code to Running Program
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");
The Edit-Compile-Test Loop