chapter 1 introduction goals to understand the activity of programming to learn about the...

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