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
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 4 5 6 7 8 } public static void main(String[] args) { // display a greeting in the console window } System.out.println("Hello, World!");
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 - javac Hello.java Compiler Execute byte codes - java Hello Interpreter
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" );