© 2006 pearson education chapter 1: computer systems presentation slides for java software...

© 2006 Pearson Education

Chapter 1: Computer Systems

Presentation slides for

Java Software Solutionsfor AP* Computer Science A

2nd Edition

by John Lewis, William Loftus, and Cara Cocking

Java Software Solutions is published by Addison-Wesley

Presentation slides are copyright 2006 by John Lewis, William Loftus, and Cara Cocking. All rights reserved.

Instructors using the textbook may use and modify these slides for pedagogical purposes.

Slides updated by [email protected]. Additional slides added from Object-Oriented Programming with Java (McGraw-Hill) instructor PowerPoint notes.

mailto:[email protected]

© 2006 Pearson Education 2

Computer Systems

We first need to explore the fundamentals of computer processing

Chapter 1 focuses on:

• components of a computer• how those components interact• how computers store and manipulate information• computer networks• the Internet and the World Wide Web• programming and programming languages• graphic systems


©The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

A History of Computers

Charles Babbage is credited as the father of computers. Although never actually built, he proposed the computing machines called Difference Engine and Analytical Engine that possessed the core characteristics of today’s computers.

Ada Lovelace, who wrote demonstration programs for Analytical Engine, is credited as the first programmer.

The first modern computer was built by Atanasoff and Berry of Iowa State University in the late 1930s.

An electromechanical computer MARK I was built by Howard Aiken of Harvard.


A History of Computers - ENIAC

The first completely electronic computer ENIAC I was built by Mauchly and Eckert of the University of Pennsylvania• Work began in 1943 and was launched in July 1946• Built to calculate artillery firing numbers for the United States • Weighed 54,000 lbs, used 17,468 vacuum tubes and used 150kW of power• Parts of it can be seen in the Smithsonian, UPenn, and other military/collegiate

locations today

Image Source: www.flickr.com


A History of Computers - ENIAC

Image Source: http://en.wikipedia.org/wiki/File:Eniac.jpg


Hardware and Software

Hardware• the physical, tangible parts of a computer• keyboard, monitor, disks, wires, chips, flash drives, etc.

Software• programs and data• a program is a series of instructions

A computer requires both hardware and software

Each is essentially useless without the other


Software Categories

Operating System• controls all machine activities• provides the user interface to the computer• manages resources such as the CPU and memory• Windows 7, Windows XP, Linux, Mac OS X Snow Leopard,

Mac OS X Mountain Lion

Application program• generic term for any other kind of software• word processors, missile control systems, games

Most operating systems and application programs have a graphical user interface (GUI)


Analog vs. Digital

There are two basic ways to store and manage data:

Analog• continuous, in direct proportion to the data

represented• music on a record album - a needle rides

on ridges in the grooves that are directly proportional to the voltages sent to the speaker

Digital• the information is broken down into

pieces, and each piece is represented discretely (not the same as discreetly)

• music on a compact disc - the disc stores numbers representing specific voltage levels sampled at specific times

Image Source: www.drummerworld.com


Digital Information

Computers store all information digitally:• numbers• text• graphics and images• video• audio• program instructions

In some way, all information is digitized - broken down into pieces and represented as numbers


Binary Numbers

Once information is digitized, it is represented and stored in memory using the binary number system

A single binary digit (0 or 1) is called a bit

Devices that store and move information are cheaper and more reliable if they have to represent only two states

A single bit can represent two possible states, like a light bulb that is either on (1) or off (0)

Permutations of bits are used to store values


Bit Permutations

1 bit

01

2 bits

00011011

3 bits

000001010011100101110111

4 bits

00000001001000110100010101100111

10001001101010111100110111101111

Each additional bit doubles the number of possible permutations


Bit Permutations

Each permutation can represent a particular item

There are 2N permutations of N bits

Therefore, N bits are needed to represent 2N unique items

21 = 2 items

22 = 4 items

23 = 8 items

24 = 16 items

25 = 32 items

1 bit ?

2 bits ?

3 bits ?

4 bits ?

5 bits ?

How manyitems can be

represented by



Decimal Number Representationdecimal

point

101102103104 100 10 1 10 2 10 3

Position Values

How the decimal number is represented.

How the decimal number is represented.

101102 100 10 1

2 4 8 7

= 2 102 + 4 101+ 8 100+ 7 10 1

= 2 100 + 4 10 + 8 1 + 7 1/10

= 200 + 40 + 8 + 7 /10 = 248.7

Example:



Binary Number Representation

binarypoint

21222324 20 2 1 2 2 2 3

Position Values

How the binary number is represented.

How the binary number is represented.

= 1 22 + 0 21 + 1 20+ 1 2 1

= 1 4 + 0 2 + 1 1 + 1 1/2

= 4 + 0 + 1 + 1/2 = 5.5

2122 20 2 1

1 0 1 1Example:


Decimal to Binary Conversion – Procedure

Convert 156 from decimal to binary• List powers of 2 in descending order until you reach the number 1

• Find highest power of 2 that can be subtracted from 156 In this case, that number is 128 Put a 1 underneath this number and subtract 128 from your number

156-128 = 28• Find the next higher power of 2 that can be subtracted from your remaining

number (28) The highest number that can be taken from 28 is 16 Put a 1 underneath this number and subtract 16 from your number

28-16=12• Continue this process until you have reached a remaining number of 0

If you do not reach 0, you made an error. Go back and retry it! Put 0s underneath all of the powers that you did not use for subtraction This string of 1s and 0s is your answer (should be 10011100)

Note: There’s a good tutorial at http://www.wikihow.com/Convert-from-Decimal-to-Binary showing pictures for each step

http://www.wikihow.com/Convert-from-Decimal-to-Binary


http://www.wikihow.com/Image:Convert-from-Decimal-to-Binary-Step-1.jpg


Binary to Decimal Conversion – Procedure

Convert 10011110 from binary to decimal• List powers of 2 in descending order until you reach the number 1

• Copy the binary sequence below your list of powers of 2, but line it up so that the last binary digit appears under the number 1 in your power of 2 list

• 512, 256, 128, 64, 32, 16, 8, 4, 2, 1

1 0 0 1 1 1 1 0• Anywhere that there is a binary 1, add the decimal number above it and keep a

running tally of this total. When done, this running tally is your answer.• 128 + 16 + 8 + 4 + 2 = 158

Note: There’s a good tutorial at http://www.wikihow.com/Convert-from-Decimal-to-Binary showing pictures for each step



http://www.wikihow.com/Image:Convert-from-Decimal-to-Binary-Step-1.jpg


Octal and Hex Representation

Very similar to binary representation, except that octal uses base-8 and hex uses base-16• Recall that binary uses 0 and 1 to represent the two values• Octal uses 0 to 7 to represent the eight values• Hex uses 0 to F to represent the sixteen values

0 to 9 represent 0 to 9 A represents 10, B represents 11, …., F represents 15

Image Source: http://www.openbookproject.net/tutorials/getdown/html/lesson5.html


Binary, Octal and Hex

A string like 11001 could represent binary, octal, hex or any other base system. We’ve been trained to use base-10 (decimal), but how do we know which one it represents when working with computers?• We use a subscript indicating the base• Example:

The first representation is binary (base-2), followed by decimal (base-10) and hex (base-16)

If there is no base specified, we assume base 10 (like logarithms!)


Decimal to Octal – Procedure

Convert 145 decimal to octal First convert the decimal number to binary

• 10010001

Split the binary up into groups of 3, starting from the right• 10 010 001

Convert each of these binary trios to an octal value between 0 and 7• 001 would be 1, 010 would be 2, 011 would be 3, 100 would

be 4, 101 would be 5, 110 would be 6 and 111 would be 7• For this problem, we get 221, so the answer is

Why not ?


Octal to Decimal – Procedure

Convert 170 octal to decimal• List powers of 8 in descending order until you reach the

number 1• Copy the binary sequence below your list of powers of 8, but

line it up so that the last octal digit appears under the number 1 in your power of 8 list

• 4096, 512, 64, 8, 1

1 7 0• Multiply each number in your list by the power of 8 above it,

and keep a running tally of this total. When done, this running tally is your answer.

• 64*1 + 8*7 + 1*0 =


Decimal to Hexadecimal – Procedure

Convert 212 decimal to hexadecimal First convert the decimal number to binary

• 11010100

Split the binary up into groups of 4, starting from the right• 1101 0100

Convert each of these binary groups to a hexadecimal value between 0 and F• 0001 would be 1, 0010 would be 2, …, 1010 would be A, 1011

would be B, 1100 would be C, 1101 would be D, 1110 would be E, and 1111 would be F

• For this problem, we get D4, so the answer is


Hexadecimal to Decimal – Procedure

Convert 195 hexadecimal to decimal• List powers of 16 in descending order until you reach the

number 1• Copy the binary sequence below your list of powers of 16,

but line it up so that the last hexadecimal digit appears under the number 1 in your power of 16 list

• 4096, 256, 16, 1

1 9 5• Multiply each number in your list by the power of 16 above it,

and keep a running tally of this total. When done, this running tally is your answer.

• 256*1 + 16*9 + 1*5 =


Conversions – Practice Quiz

These are similar to the upcoming quiz questions…

1. Convert to binary


3. Convert to decimal



6. Convert to hexadecimal

7. Convert to octal

8. Convert to decimal


10.Convert to binary


Conversions – Practice Quiz Answers


Representing Text Digitally

For example, every character is stored as a number, including spaces, digits, and punctuation

Corresponding upper and lower case letters are separate characters

H i , H e a t h e r .

72 105 44 32 72 101 97 116 104 101 114 46


ASCII Conversion Table



Computer Architecture

CPUCPU

OutputDevicesOutputDevices

Commu-nicationDevices

Commu-nicationDevices

InputDevicesInput

Devices

RAMRAM

StorageDevicesStorageDevices


The Central Processing Unit

A CPU is on a chip called a microprocessor

It continuously follows the fetch-decode-execute cycle:

fetch

Retrieve an instruction from main memory

decode

Determine what theinstruction is

execute

Carry out theinstruction



The CPU contains:

Arithmetic / Logic Unit

Registers

Control Unit

Small storage areas

Performs calculations and makes decisions

Coordinates processing steps



The speed of a CPU is controlled by the system clock

The system clock generates an electronic pulse at regular intervals

The pulses coordinate the activities of the CPU

The speed is measured in hertz, though today speeds are so high that we generally list it in gigahertz (GHz)


Memory

Main memory is volatile - stored information is lost if the electric power is removed

Secondary memory devices are nonvolatile

Main memory and disks are direct access devices - information can be reached directly

The terms direct access and random access often are used interchangeably

A magnetic tape is a sequential access device since its data is arranged in a linear order - you must get by the intervening data in order to access other information


RAM vs. ROM

RAM - Random Access Memory (direct access)

ROM - Read-Only Memory

The terms RAM and main memory are basically interchangeable

ROM could be a set of memory chips, or a separate device, such as a CD ROM

Both RAM and ROM are random (direct) access devices!

RAM probably should be called Read-Write Memory


Memory

Main memory is divided into many memory locations (or cells)

92789279

9280928192829283928492859286

Each memory cell has a numeric address, which uniquely identifies it


Storing Information

92789279

9280928192829283928492859286

Large values arestored in consecutivememory locations

10011010Each memory cell stores a set number of bits (usually 8 bits, or one byte)


Storage Capacity

Every memory device has a storage capacity, indicating the number of bytes it can hold

Capacities are expressed in various units:

KB 210 = 1024

MB 220 (over 1 million)

GB 230 (over 1 billion)

TB 240 (over 1 trillion)

Unit Symbol Number of Bytes

kilobyte

megabyte

gigabyte

terabyte


Storage Notation

Bytes are represented with a B, bits with a b• 600 bits = 600 b• 80 bytes = 80 B• 50,411,918 bytes = 50,411,918 B

Similar to distances and sizes it is convenient to represent large numbers with Kilo-, Mega-, Giga-, etc.• Capitalization is important here as well• 1 kB = 1000 bytes, or 8000 bits• 1 KB = , or 1024 bytes (8,192 bits)

As a general rule of thumb, do not use lowercase letters other than to distinguish bits vs. bytes• Example:


Storage Notation

File sizes are measured in bytes (KB, MB, GB, etc.)• Example: Word document is 345 KB

Streaming rates such as your Internet connection speed is measured in bits per second (bps, Kbps, Mbps, Gbps, etc.) Example: Comcast may advertise a download speed of 25 Mbps Test your own speed at http://www.speedtest.net/ or on mobile

phones at http://www.speedtest.net/mobile.php Mr. Bixler’s results below

Google fiber promises speeds of 1 Gbps over fiber optic cables! https://fiber.google.com/about/

http://www.speedtest.net/

http://www.speedtest.net/

http://www.speedtest.net/mobile.php

https://fiber.google.com/about/

https://fiber.google.com/about/


Compact Discs

A CD-ROM is portable read-only memory

A microscopic pit on a CD represents a binary 1 and a smooth area represents a binary 0

A low-intensity laser reflects strongly from a smooth area and weakly from a pit

A CD-Recordable (CD-R) drive can be used to write information to a CD once

A CD-Rewritable (CD-RW) can be erased and reused

The speed of a CD drive (48x) describes the maximum data transfer speed. Writing is typically much slower than reading.


DVDs A DVD is the same size as a CD, but can store much more

information

The format of a DVD stores more bits per square inch

• How can it do that? Can a DVD burner also burn CDs? Can a CD burner also burn DVDs?

A CD can store 650 or 700 MB, while a standard DVD can store 4.7 GB• A double sided DVD can store 9.4 GB

• Other advanced techniques can bring the capacity up to 17.0 GB

• HD-DVD (Toshiba and NEC) vs. Blu-ray (Sony) battle Who won?

There are various recordable DVD technologies – the market will determine which will dominate


Comparison of HDD and SDD

Hard Disk Drive (HDD)• Uses magnetism to store data on a rotating platter• Read/write head floats above spinning platter to read/write

data• Costs only about $0.10 per gigabyte• Uses 6-7 Watts of power and makes small amount of noise

Solid State Drive (SDD)• Uses embedded processor (its “brain”) to perform read/write

operations• Costs about $1.00 per gigabyte, and dropping quickly• Uses 2-3 Watts of power (conserves battery)• No moving parts results in high reliability and quiet operation• Boots up Windows 7 about twice as fast as a HDD

Also compatible with all other OSs


A Computer Specification

Consider the following specification for a personal computer:

• 2.4 GHz Intel Core i7-2760QM Processor• 4 GB RAM• 750 GB Hard Disk Drive• Windows 7 64-bit Operating System• 48x CD-RW / DVD-RW Combo Drive • 24” LCD Display with 1920 x 1200 resolution

What does it all mean?


Monitor

The size of a monitor (for example, 24") is measured diagonally, like a television screen

Most monitors these days have multimedia capabilities: text, graphics, video, etc.

A monitor has a certain maximum resolution , indicating the number of picture elements, called pixels, that it can display (such as 1920 by 1200)

High resolution (more pixels) produces sharper pictures


Modem

Data transfer devices allow information to be sent and received between computers

Many computers include a modulator-demodulator or modem, which allows information to be moved across a telephone line

A data transfer device has a maximum data transfer rate

A newer cable modem, for instance, may support a data transfer rate of 160 Mbps


Networks

A network is two or more computers that are connected so that data and resources can be shared

Most computers are connected to some kind of network

Each computer has its own network address, which uniquely identifies it among the others

A file server is a network computer dedicated to storing programs and data that are shared among network users


Network Connections

Each computer in a network could be directly connected to every other computer in the network

These are called point-to-point connections

This technique is not practical formore than a few close machines

Adding a computer requiresa new communication linefor each computer alreadyin the network


Network Connections

Most networks share a single communication line

Adding a new computer to the network is relatively easy

Network traffic must taketurns using the line, whichintroduces delays

Often information is brokendown in parts, called packets,which are sent to the receivingmachine and then reassembled


Local-Area Networks

LAN

A Local-Area Network(LAN) covers a smalldistance and a smallnumber of computers

A LAN often connects the machinesin a single room or building


Wide-Area Networks

LAN

A Wide-Area Network (WAN)connects two or more LANs,often over long distances

A LAN usually is ownedby one organization, buta WAN often connectsgroups in different countries

LAN


The Internet

The Internet is a WAN which spans the entire planet

The word Internet comes from the term internetworking, which implies communication among networks

It started as a United States government project, sponsored by the Advanced Research Projects Agency (ARPA) - originally it was called the ARPANET

Internet grew quickly throughout the 1980s and 90s and has exploded since

Less than 600 computers were connected to the Internet in 1983; by the year 2000 there were over 10 million; in 2011, more than 2.2 billion people use the Internet


TCP/IP

A protocol is a set of rules that determine how things communicate with each other

The software which manages Internet communication follows a suite of protocols called TCP/IP

The Internet Protocol (IP) determines the format of the information as it is transferred

The Transmission Control Protocol (TCP) dictates how messages are reassembled and handles lost information


IP and Internet Addresses

Each computer on the Internet has a unique IP address, such as:

204.192.116.2

Most computers also have a unique Internet name, which also is referred to as an Internet address:

spencer.villanova.edu

kant.gestalt-llc.com

The first part indicates a particular computer (spencer)

The rest is the domain name, indicating the organization (villanova.edu)


Domain Names

The last part of each domain name, called a top-level domain (TLD) indicates the type of organization:

educomorgnet

- educational institution- commercial entity- non-profit organization- network-based organization

Sometimes the suffixindicates the country: New TLDs have

recently been added:

aero, asia, biz, cat, coop, info, intjobs, mobi, museum, name, pro

tel, travel, xxx

ukaucase

- United Kingdom- Australia- Canada- Sweden


Domain Names

A domain name can have several parts

Unique domain names mean that multiple sites can have individual computers with the same local name

When used, an Internet address is translated to an IP address by software called the Domain Name System (DNS)

There is no one-to-one correspondence between the sections of an IP address and the sections of an Internet address


The World Wide Web

The World Wide Web allows many different types of information to be accessed using a common interface

A browser is a program which accesses and presents information

• text, graphics, video, sound, audio, executable programs

A Web document usually contains links to other Web documents, creating a hypermedia environment

The term Web comes from the fact that information is not organized in a linear fashion


The World Wide Web

Web documents are often defined using the HyperText Markup Language (HTML)

Information on the Web is found using a Uniform Resource Locator (URL):

http://www.lycos.com

http://www.villanova.edu/webinfo/domains.html

ftp://java.sun.com/applets/animation.zip

A URL indicates a protocol (http), a domain, and possibly specific documents


Problem Solving

The purpose of writing a program is to solve a problem

The general steps in problem solving are:

• Understand the problem• Dissect the problem into manageable pieces• Design a solution• Consider alternatives to the solution and refine it• Implement the solution• Test the solution and fix any problems that exist


Problem Solving

Many software projects fail because the developer didn't really understand the problem to be solved

We must avoid assumptions and clarify ambiguities

As problems and their solutions become larger, we must organize our development into manageable pieces

This technique is fundamental to software development

We will dissect our solutions into pieces called classes and objects, taking an object-oriented approach


History of Programming Languages

Numerous languages have been developed since the early 2000’s (Cobra, Clojure, Go), but none have seen the adoption rates that previous programming languages have found.

Source: http://en.wikipedia.org/wiki/Timeline_of_computing


Programming Community Index

Developed by TIOBE, a software company Tracks popularity of programming languages

Source: http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html

http://www.tiobe.com/index.php/

http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html


Longer Term View of Language Popularity

They have lost some market shared, but C and Java are clearly still the leaders of the programming world

Source: http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html

http://www.tiobe.com/index.php/

http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html


Java

A programming language specifies the words and symbols that we can use to write a program

A programming language employs a set of rules that dictate how the words and symbols can be put together to form valid program statements

The Java programming language was created by Sun Microsystems, Inc.

It was introduced in 1995 and it's popularity has grown quickly since, though an increasing number of languages have emerged in recent years

It is an object-oriented language


Java Program Structure

In the Java programming language:• A program is made up of one or more classes• A class contains one or more methods• A method contains program statements

These terms will be explored in detail throughout the course

A Java application always contains a method called main

See Lincoln.java (page 27)



public class MyProgram

{

}

// comments about the class

class header

class body

Comments can be placed almost anywhere



public class MyProgram

{

}

public static void main (String[] args)

{

}

// comments about the class

// comments about the method

method headermethod body


Comments

Comments in a program are called inline documentation

They should be included to explain the purpose of the program and describe processing steps

They do not affect how a program works

Java comments can take three forms:

// this comment runs to the end of the line

/* this comment runs to the terminating symbol, even across line breaks */

/** this is a javadoc comment */


Identifiers

Identifiers are the words a programmer uses in a program

An identifier can be made up of letters, digits, the underscore character ( _ ), and the dollar sign

Identifiers cannot begin with a digit

Java is case sensitive - Total, total, and TOTAL are different identifiers

By convention, Java programmers use different case styles for different types of identifiers, such as• title case for class names - Lincoln

• upper case for constants - MAXIMUM


Identifiers

Sometimes we choose identifiers ourselves when writing a program (such as Lincoln)

Sometimes we are using another programmer's code, so we use the identifiers that they chose (such as println)

Often we use special identifiers called reserved words that already have a predefined meaning in the language

A reserved word cannot be used in any other way


Reserved Words

The Java reserved words:

abstractassertbooleanbreakbytecasecatchcharclassconstcontinuedefaultdodouble

elseenumextendsfalsefinalfinallyfloatforgotoifimplementsimportinstanceofint

interfacelongnativenewnullpackageprivateprotectedpublicreturnshortstaticstrictfp

superswitchsynchronizedthisthrowthrowstransienttruetryvoidvolatilewhile


White Space

Spaces, blank lines, and tabs are called white space

White space is used to separate words and symbols in a program

Extra white space is ignored

A valid Java program can be formatted in many ways

Programs should be formatted to enhance readability, using consistent indentation

See Lincoln2.java (page 33)

See Lincoln3.java (page 34)


Language Levels

There are four programming language levels:• machine language• assembly language• high-level language• fourth-generation language

Each type of CPU has its own specific machine language

The other levels were created to make it easier for a human being to read and write programs



Chapter 0 - 71

Programming Languages

Four primary levels of programming languages:• Machine Languages

Machine language instructions are binary coded and very low level Examples are ARM, MIPS

• Assembly Languages Assembly language allows symbolic programming. Requires an

assembler to translate assembly programs into machine programs Examples are Emu8086 and PAL-III

• High-level Languages High-level language provides a very high conceptual model of

computing. Requires a compiler to translate high-level programs into assembly programs

Examples are C and Java• Fourth-generation Languages

Build around database systems and mostly used in the commercial sector

Examples are Oracle Express 4GL and SAS


Programming Languages

A program must be translated into machine language before it can be executed on a particular type of CPU

This can be accomplished in several ways

A compiler is a software tool which translates source code into a specific target language

Often, that target language is the machine language for a particular CPU type

The Java approach is somewhat different


Java Translation

The Java compiler translates Java source code into a special representation called bytecode

Java bytecode is not the machine language for any traditional CPU

Another software tool, called an interpreter, translates bytecode into machine language and executes it

Therefore the Java compiler is not tied to any particular machine

Java is considered to be architecture-neutral


Java Translation

Java sourcecode

Machinecode

Javabytecode

Javainterpreter

Bytecodecompiler

Javacompiler


Java Translation

We now know the translation process, but why not just write the code in bytecode or machine code?

Example: Java source code Bytecode for same Java source code

Machine code would be all 0s and 1s!• Above machine code too long to fit here, but below example tells the CPU to load a value into register

8, taken from the memory cell found 68 cells after the location found in register 3?!?

Source: http://en.wikibooks.org/wiki/Java_Programming/Byte_Code


Development Environments

There are many environments for developing Java software:

• Sun Java Development Kit (JDK)• Sun NetBeans• Borland JBuilder• MetroWerks CodeWarrior• Microsoft Visual J++• IBM Eclipse• Monash BlueJ

Though the details of these environments differ, the basic compilation and execution process is essentially the same


Syntax and Semantics

The syntax rules of a language define how we can put together symbols, reserved words, and identifiers to make a valid program

The semantics of a program statement define what that statement means (its purpose or role in a program)

A program that is syntactically correct is not necessarily logically (semantically) correct

A program will always do what we tell it to do, not what we meant to tell it to do


Errors

A program can have three types of errors

The compiler will find syntax errors and other basic problems (compile-time errors)

• If compile-time errors exist, an executable version of the program is not created

A problem can occur during program execution, such as trying to divide by zero, which causes a program to terminate abnormally (run-time errors)

A program may run, but produce incorrect results, perhaps using an incorrect formula (logical errors)


Basic Program Development

errors

errors

Edit andsave program

Compile program

Execute program andevaluate results


Introduction to Graphics

The last one or two sections of each chapter of the textbook focus on graphical issues

Most computer programs have graphical components

A picture or drawing must be digitized for storage on a computer

A picture consists of pixels, and each pixel is stored separately


Representing Color

A black and white picture can be stored using one bit per pixel (0 = white and 1 = black)

A colored picture requires more information; there are several techniques for representing colors

For example, every color can be represented as a mixture of the three additive primary colors Red, Green, and Blue

In Java, each color is represented by three numbers between 0 and 255 that collectively are called an RGB value

With this in mind, how can we store images digitally? How would this also allow for the storage of video?


Coordinate Systems

Each pixel can be identified using a two-dimensional coordinate system

When referring to a pixel in a Java program, we use a coordinate system with the origin in the top-left corner

Y

X(0, 0)

(112, 40)

112

40


Summary

Chapter 1 has focused on:

• components of a computer• how those components interact• how computers store and manipulate information• computer networks• the Internet and the World Wide Web• programming and programming languages• graphic systems

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