chapter 1 introduction goals to understand the activity of programming to learn about the...
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CHAPTER 1
INTRODUCTIONGOALS 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 Assembleriload intRatebipush 100if_icmpgt intError
High-level languageif (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 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 {
3 public static void main(String[] args)
4 {
5 // display a greeting in the console window
6 System.out.println("Hello, World!");
7 }
8 }
A simple program public class ClassName public static void main(String[] args) // commentMethod 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 -- Interpreterjava 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