Download Chapter 1 - Computer and Information Sciences

CS 201
Introduction to
Object-Oriented Programming
Dr. Jeff Gray
gray (at) cis.uab.edu
http://www.cis.uab.edu/gray
Tue/Thu: 3pm-5pm
Course web page:
http://www.cis.uab.edu/gray/cs201/
Agenda – Thursday June 1
• Today




Motivation for Studying Computer Science
Opportunities at UAB CIS
The Need for Good Engineering of Software
Begin Chapter 1
• Next Tuesday
 First Lab in the Morning
 Finish Chapter 1
• Next Thursday
 Begin Chapter 2
 Tour of Supercomputer and Visualization Room
• Be on Time for Class!
Exciting New Additions This Summer
Sudoku Homework Sequence
RoboCode Labs
Motivation for Studying CS
Software is Everywhere
• Think of some of the things that entertain and enrich
your daily life
• All of the above are driven by software
• Software developers equipped with a computer science
degree have opportunities to work on exciting and
cutting-edge projects
Software is Everywhere
• 98% of all microprocessors control devices other than desktop
computers
 Automobiles, airplanes, televisions, copiers, razors…
> 1M
SLOC
15-20Kb
1-1.5Mb
>10Mb embedded software
• These devices also need software and often require strong
technical skills to develop
The Demand for Computer Scientists
• Computing will continue to be a dominant science on
which every other science, engineering, and business
discipline will increasingly rely. Almost all major
technology breakthroughs in the future will involve
computing.
• College graduates in the 21st century cannot afford to be
ignorant of Computer Science principles. This is
important for Alabama, which is one of the major
developing technology centers in our nation. Having a
technology literate workforce will be necessary for
continued economic growth.
The Demand for Computer Scientists
Offshore hysteria: Many companies with
high paying jobs within the US are
unable to fill positions with computer
scientists.
Source: http://money.cnn.com/magazines/moneymag/bestjobs/top50/index.html
The Demand for Computer Scientists
• According to Business 2.0 magazine, 5 of the top-10
growing jobs have a computer science focus
Source: http://money.cnn.com/magazines/business2/nextjobboom/
The Demand for Computer Scientists
• National Job Outlook
 $50,500 is the expected starting salary for
computer science degrees in the class of 2006
(among top 5 highest starting salaries)
 1000s of openings each at Microsoft Game
Studios, Electronic Arts, Epic Games, Google
 Epic Games President: “We do not hire anyone
under $100k”
The Demand for Computer Scientists
• Local Job Outlook
 In Birmingham, a large financial software company recently
had a need for 200 Java programmers; exceeded
university’s ability to deliver employees
 CTS hiring several new developers each month
 Summary of recent openings in Birmingham:
•
•
•
•
•
•
•
•
•
•
JAVA/J2EE/EJB ($60/hr)
Peoplesoft (Technical - $85/hr) (Functional - $95/hr)
SAP Technical ($85/hr), SAP Functional ($95/hr)
Corba ($55/hr)
Oracle DBA ($70/hr)
DB2 DBA ($70/hr)
Sybase DBA ($75/hr)
.Net,vb.net,C#,asp.net ($60/hr)
C/C++ ($55/hr)
Cobol ($55/hr)
The Potential for Alabama
Source: Entrepreneur magazine
Myth of Computer Science
• According to the Alabama Learning Exchange (ALEX)1,
computing is equated to learning Microsoft Word and various
mechanical tasks; this is not Computer Science!
1
http://alex.state.al.us/standardAll.php?grade=9&subject=TC&summary=2
High School Outreach at UAB CIS
Mentoring for Science Fair Competitions
• Weekly mentoring at UAB throughout
academic year; students treated like a
PhD student with office space
www.cis.uab.edu/gray/Pubs/jerrod-sutton.pdf
Computer Graphics Camp
• Week-long summer camp
in computer graphics
• Students use C++ and
OpenGL
to
create
projects
focused
on
geometric
modeling,
algorithm
visualization,
and motion design
www.cis.uab.edu/cscamp/
Summer Robotics Internship
• Seven-week internship
• Students taught Java through series of
robotics projects
www.cis.uab.edu/heritage
High School Programming Contest
• May 13, 2006
• 46 students from 12
schools (Huntsville to
Mobile)
• 6 problems in 3 hours
• Prizes: Xbox, software,
books, gift certificates
www.cis.uab.edu/progams/hspc
Opportunities at UAB CIS
Reasons to Consider UAB CIS
• Scholarship Availability
 For outstanding high school students, UAB offers several
scholarships to incoming freshmen (from $2000-$8000 per
year)
 The CIS Department offers the Fontana Scholarship each
year to two CIS students (typically awarded to Junior and
Senior students). This scholarship provides $4,000 over the
academic year.
• Outstanding Faculty
 The 11 professors and instructors in the CIS Department
obtained their degrees from the top schools in the country
(e.g., Cal Tech, Cornell, Northwestern, Pennsylvania, and
Vanderbilt). In addition to being leaders in their fields, our
professors are dedicated to spending time with students.
Reasons to Consider UAB CIS
• Excellence in Research and Service
 UAB is the largest employer in the state of Alabama and is
the only school in Alabama with the highest research rating
(“RU/VH”), which is based on grant funding and PhD
production. The University has over $500M in external
funding this year, which is several times that of all other
universities in Alabama combined.
 Research in the CIS department is funded by the Army
Research Office (ARO), Defense Advanced Research
Projects Agency (DARPA), International Business Machines
(IBM), National Science Foundation (NSF), National
Institutes of Health (NIH), and the Office of Naval Research
(ONR).
Reasons to Consider UAB CIS
• Outstanding Facilities
 Fastest computer in the state of Alabama!
UAB CIS recently acquired a 128 node
compute cluster which has been
benchmarked at 1.41 teraflops per
second. Fastest in Alabama and one
of the fastest in the whole Southeast.
 New visualization wall
UAB CIS recently acquired a 13
megapixel, nine tile visualization wall
that measures approximately 10' wide
by 8' high.
Reasons to Consider UAB CIS
• Undergraduate Research Opportunities
 For undergraduate students with a high GPA, there is an
opportunity to do Honors research with faculty members.
There is a special course available that allows a student to
be mentored by a faculty member in a manner that provides
the student a taste of the graduate school experience.
Students participating in CIS Honors receive a special
designation on their diploma at graduation.
 During Fall 2005, the CIS department created an
Undergraduate Honors Research Lab to host those students
participating in Honors research. The students in this
special lab will have exclusive access to high-end
computers, with accommodations similar to those of
doctoral students.
Possible Honors Mentoring Ideas
• LEGO will release the brand new NXT robot over the
summer
 Exciting new capabilities include wireless communication
and vision
• At UAB, we will have 5 of these robots for
experimentation purposes (July 2006)
Possible Mentoring Ideas
• Target Recognition in a Rescue Mission
 A group of coordinated robots will work together to conduct
a search/rescue mission
• Sniper Identification
 A group of autonomous robots will be used to isolate the
location of sniper fire in a military application (using
triangulation)
• Speech and Vision Recognition
 Voice controlled commands to a robot that also can use the
vision camera to avoid colliding with objects
• Game Playing Robot
 Tic-tac-toe; Othello
 2-on-2 soccer
• YOUR IDEA HERE!
 Of course, we encourage creativity if you have new ideas!
Reasons to Consider UAB CIS
• Undergraduate Research Opportunities
 CIS undergraduates are awarded summer internships to participate in
special research programs sponsored by the National Science
Foundation. The students participating in these opportunities continue
their research throughout the academic year and prepare research talks
and papers that are published at regional conferences. Over the past
two years, CIS students placed in the top 3 at the ACM Mid-southeast
conference in Gatlinburg, Tennessee.
3 First Place Winners: UAB CIS students
received first place in all categories
(Undergrad, Masters, PhD) amid students
from 7 states.
Reasons to Consider UAB CIS
• Programming Contest Team
 Each year, the CIS department sends our top 9 students to
compete in the annual ACM programming contest (held the last
few years in Melbourne, Florida). To prepare students for this
competition, a new course has been introduced in the curriculum
that teaches students problem solving techniques not typically
covered in core courses.
In 2005, the UAB programming team placed
among the top 25 out of 64 universities and had
the highest score among Alabama Universities.
The Need for Software Engineering
• Programming “In the Large” vs “In the Small”
Poor Engineering leads to ad-hoc structure!
The result of continuous building
without any thought toward design.
Result:
Stairs leading to ceiling;
Windows in the middle of room;
Doors opening to wall;
Non-intuitive floor plan!.
Poor Engineering Has Disastrous Consequences!
Aerodynamic phenomena in suspension
bridges were not adequately understood in
the profession nor had they been addressed
in this design. New research was necessary
to understand and predict these forces.
The remains, located on the bottom of the
Sound, are a permanent record of man's
capacity to build structures without fully
understanding the implications of the design.
http://www.nwrain.net/~newtsuit/recoveries/narrows/narrows.htm
Poor Engineering Has Disastrous Consequences!
$7 Billion Fire Works – One Bug, One Crash
On 4 June 1996, the maiden flight of the Ariane 5 launcher
ended in a failure. Only about 40 seconds after initiation of
the flight sequence, at an altitude of about 3700 m, the
launcher veered off its flight path, broke up and exploded.
The failure of the Ariane 501 was caused by the complete
loss of guidance and attitude information 37 seconds after
start of the main engine ignition sequence (30 seconds
after lift- off). This loss of information was due to
specification and design errors in the software of the
inertial reference system.
The launcher started to disintegrate at about H0 + 39 seconds because of high aerodynamic loads due to an angle of attack of more than 20 degrees that led to separation of the boosters from the
This angle of attack was caused by full nozzle deflections of the solid boosters and the Vulcain main engine.
These nozzle deflections were commanded by the On-Board Computer (OBC) software on the basis of data transmitted by the active Inertial Reference System (SRI 2). Part of these data at that ti
The reason why the active SRI 2 did not send correct attitude data was that the unit had declared a failure due to a software exception.
The OBC could not switch to the back-up SRI 1 because that unit had already ceased to function during the previous data cycle (72 milliseconds period) for the same reason as SRI 2.
The internal SRI software exception was caused during execution of a data conversion from 64-bit floating point to 16-bit signed integer value. The floating point number which was converted had a
The error occurred in a part of the software that only performs alignment of the strap-down inertial platform. This software module computes meaningful results only before lift-off. As soon as the lau
The alignment function is operative for 50 seconds after starting of the Flight Mode of the SRIs which occurs at H0 - 3 seconds for Ariane 5. Consequently, when lift-off occurs, the function continue
The Operand Error occurred due to an unexpected high value of an internal alignment function result called BH, Horizontal Bias, related to the horizontal velocity sensed by the platform. This value
The value of BH was much higher than expected because the early part of the trajectory of
Ariane 5 differs from that of Ariane 4 and results in considerably higher horizontal velocity values.
http://java.sun.com/people/jag/Ariane5.html
http://www.around.com/ariane.html
http://archive.eiffel.com/doc/manuals/technology/contract/ariane/page.htm
Two Techniques for Controlling Structure
• Decomposition
 Technique for dividing systems into modules
 Well-structured program is one with minimal
interconnections between its modules (low-coupling)
 More to be said in later lectures
• Precise Specification
 “precisely describing the assumptions that the designers
of one module are permitted to make about other
modules”
 More also to be said on this later
• Some examples of why it is easier in other
“engineering” endeavours…
Decomposition and Simple Specification
The prong and receptacle
parts of a Lego™ block
have been unchanged
since 1932 [Lego, 2002].
Simple Interface Specification
Since around 1850, the standard
dimensions for an “air cell” masonry
brick in the United States has been
2.5 x 3.75 x 8 inches [Chrysler and
Escobar, 2000].
Even building a dog house takes some engineering
From http://www.ttyler.8m.com/Dog%20House.htm
Initially started as a "basic" dog house but soon turned into
a masterpiece of quality workmanship. Total time spent
was 8 hours at a cost of $110 US.
Start with a piece of paper and a idea: Design your dog
house to the size and quantity of your dogs. A perfectly built
home is worthless if its to small to properly accommodate your
dog.
Framing: The framing process should be constructed with 2x4's
or rip them in half for smaller homes. A removable roof should
be incorporated in assisting the future cleaning and
maintenance.
Wall Covering: Should be tong & grove for a tight fit, no
warping, and to cut down on cross drafts. For large homes,
plywood is a economical material that can be used.
Roof: 30 year home shingles cut down to the proper size. As
for this house, an oriental piece was constructed then topped of
with a copper fence post top. An additional hours work and $15
cost was needed
Trim & Finishing Touches: Trim can add a lot to the astidics of
your dog house. Trim can be bought with may different
variations or with some craftsmanshipcan can be made with the
use of a router.
Sanding & Paint: Sink all nails below the surface and cover
with wood filler. Prepare surface for painting by sanding wood
filler, rough spots, and blemishes.
Let’s Get Started!!!!!!
Introduction
Chapter
5TH EDITION
Lewis & Loftus
java
Software Solutions
Foundations of Program Design
© 2007 Pearson Addison-Wesley. All rights reserved
1
Focus of the Course
• Object-Oriented Software Development
 problem solving
 program design, implementation, and testing
 object-oriented concepts
•
•
•
•
•
classes
objects
encapsulation
inheritance
polymorphism
 graphical user interfaces
 the Java programming language
Introduction
• 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
an introduction to Java
an overview of object-oriented concepts
Outline
Computer Processing
Hardware Components
Networks
The Java Programming Language
Program Development
Object-Oriented Programming
Hardware and Software
• Hardware
 the physical, tangible parts of a computer
 keyboard, monitor, disks, wires, chips, 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
CPU and Main Memory
Central
Processing
Unit
Primary storage area
for programs and data
that are in active use
Synonymous with
RAM
Main
Memory
Chip that executes
program commands
Intel Pentium 4
Sun ultraSPARC III
Secondary Memory Devices
Secondary memory
devices provide
long-term storage
Hard disks
Floppy disks
ZIP disks
Writable CDs
Writable DVDs
Tapes
Central
Processing
Unit
Information is moved
between main memory
and secondary memory
as needed
Hard Disk
Main
Memory
Floppy Disk
Input / Output Devices
Monitor
Keyboard
Monitor screen
Keyboard
Mouse
Joystick
Bar code scanner
Touch screen
Central
Processing
Unit
I/O devices facilitate
user interaction
Hard Disk
Main
Memory
Floppy Disk
Software Categories
• Operating System




controls all machine activities
provides the user interface to the computer
manages resources such as the CPU and memory
Windows XP, Unix, Linux, Mac OS
• 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 separately
 music on a compact disc - the disc stores numbers
representing specific voltage levels sampled at specific
times
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
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
Hi, Heather.
72 105 44 32 72 101 97 116 104 101 114 46
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
0
1
2 bits
00
01
10
11
3 bits
000
001
010
011
100
101
110
111
4 bits
0000 1000
0001 1001
0010 1010
0011 1011
0100 1100
0101 1101
0110 1110
0111 1111
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
1 bit ?
21 = 2 items
How many
items can be
represented by
2
2 bits ?
2 = 4 items
3 bits ?
23 = 8 items
4 bits ?
24 = 16 items
5 bits ?
25 = 32 items
Outline
Computer Processing
Hardware Components
Networks
The Java Programming Language
Program Development
Object-Oriented Programming
A Computer Specification
• Consider the following specification for a personal
computer:






2.8 GHz Pentium 4 Processor
512 MB RAM
80 GB Hard Disk
48x CD-RW / DVD-ROM Combo Drive
17” Video Display with 1280 x 1024 resolution
56 Kb/s Modem
• What does it all mean?
Memory
9278
9279
9280
9281
9282
9283
9284
9285
9286
Main memory is divided
into many memory
locations (or cells)
Each memory cell has a
numeric address, which
uniquely identifies it
Storing Information
9278
9279
9280
9281
9282
9283
9284
9285
9286
10011010
Each memory cell stores a
set number of bits (usually
8 bits, or one byte)
Large values are
stored in consecutive
memory locations
Storage Capacity
• Every memory device has a storage capacity,
indicating the number of bytes it can hold
• Capacities are expressed in various units:
Unit
Symbol
Number of Bytes
kilobyte
KB
210 = 1024
megabyte
MB
220 (over 1 million)
gigabyte
GB
230 (over 1 billion)
terabyte
TB
240 (over 1 trillion)
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
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 indicates how fast (max) it
can read and write information to a CD
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
• A CD can store 650 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
• Like CDs, there are DVD-R and DVD-RW discs
The Central Processing Unit
• A CPU is on a chip called a microprocessor
• It continuously follows the fetch-decode-execute
cycle:
Retrieve an instruction from main memory
fetch
execute
Carry out the
instruction
decode
Determine what the
instruction is
The Central Processing Unit
• The CPU contains:
Arithmetic / Logic Unit
Control Unit
Registers
Performs calculations
and makes decisions
Coordinates
processing steps
Small storage
areas
The Central Processing Unit
• 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 usually measured in gigahertz (GHz)
Monitor
• The size of a monitor (17") 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 1280 by 1024)
• 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 modem, for instance, may have a data transfer
rate of 56,000 bits per second (bps)
Agenda – Thursday June 6
• Summary from Last Lecture




Motivation for studying CS and UAB opportunities
Analog vs Digital
Binary Numbers
Hardware Categories
• Today
 Textbook Issue
 First Lab in the Morning
 Finish Chapter 1
• Thursday
 Begin Chapter 2
 Tour of Supercomputer and Visualization Room
• Be on Time for Class!
Review of Binary Numbers:
Converting Binary to Decimal
• Consider what the decimal number “1,234” means:
 1234 = 1000 + 200 + 30 + 4

= 1*1000 + 2*100 + 3*10 + 4 * 1

= 1*103 + 2*102 + 3*101 + 4*100
• In general, na…n1n0 represented in base “b” is:
 na…n1n0 = na*ba + … + n1*b1 + n0*b0
• Apply this to generalization to binary “01101100” (b=2)
 01101100 = 0*27 + 1*26 + 1*25 + 0*24 + 1*23 + 1*22 + 0*21 + 0*20

= 0*128 + 1*64 + 1*32 + 0*16 + 1*8 + 1*4 + 0*2 + 0*1

=0
+ 64 + 32 + 0
+8 +4 +0 +0

= 64 + 32 + 8 + 4

= 108
Review of Binary Numbers:
Converting Decimal to Binary
 Step 1: See if the number is divisible by 2.
• If it is divisible by 2, write ‘0’ and divide by 2 to get the next
number.
• If the number, on the other hand, is indivisible by 2, write a ‘1’,
then subtract 1 from the number and divide by two to get the
next number.
 Step 2: Continue this process, writing each ‘1’ or ‘0’ to the left
of the previous 1 or 0, until the number which we are left to
divide by is 0.
 Step 3: You should always check your answer to make sure
that your conversion is correct.
Review of Binary Numbers:
Converting Decimal to Binary
Lets convert the decimal number 241 to binary
 Step 1: Divide by two. Since 241 is indivisible, we write a 1. Then we subtract 1 from 241 to get
240 and divide by two to get 120.
Result: 1
 Step 2: Divide by two. Since 120 is divisible, we write a 0 to the left of the previous number and
divide by two to get 60.
Result: 01
 Step 3: Divide by two. Since 60 is divisible, we write a 0 to the left of the previous number and
divide by two to get 30.
Result: 001
 Step 4: Divide by two. Since 30 is divisible, we write a 0 to the left of the previous number and
divide by two to get 15.
Result: 0001
 Step 5: Divide by two. Since 15 is indivisible, we write a 1 to the left of the previous number. Then
we subtract 1 from 15 to get 14 and when we divide we get 7.
Result: 10001
 Step 6: Divide by two. Since 7 is indivisible, we write a 1 to the left of the previous numbers. Then
we subtract 1 from 7 to get 6 and when we divide we get 3.
Result: 110001
 Step 7: Divide by two. Since 3 is indivisible, we write a 1 to the left of the previous numbers. Then
we subtract 1 from 3 to get 2 and when we divide we get 1.
Result: 1110001
 Step 8: Divide by two. Since 1 is indivisible, we write a 1 to the left of the previous numbers. Then
we subtract 1 from 1 to get 0, which means we are finished.
Result: 11110001
Review of Binary Numbers
• Some helpful references (thanks to Adam Dane)
 Cartoon
• http://static.instructables.com/data/uuid/EB/9C7EE0/7C8710
28A786001143E7E506/EB9C7EE07C871028A786001143E7E5
06.pdf
 Binary game
• http://forums.cisco.com/CertCom/game/binary_game_page.
htm?site=celc
Outline
Computer Processing
Hardware Components
Networks
The Java Programming Language
Program Development
Object-Oriented Programming
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 (similar for web server and print
server)
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
Adding a computer requires
a new communication line
for each computer already
in the network
This technique is not practical for
more than a few close machines – why?
Network Connections
• Most networks share a single communication line
• Adding a new computer to the network is relatively
easy
Network traffic must take
turns using the line, which
introduces delays
Often information is broken
down in parts, called packets,
which are sent to the receiving
machine and then reassembled
Local-Area Networks
A Local-Area Network
(LAN) covers a small
distance and a small
number of computers
LAN
A LAN often connects the machines
in a single room or building
Wide-Area Networks
A Wide-Area Network (WAN)
connects two or more LANs,
often over long distances
LAN
LAN
A LAN usually is owned
by one organization, but
a WAN often connects
groups in different
countries
The Internet
• The Internet is a WAN which spans the entire
planet
• The word Internet comes from the term
internetworking
• It started as a United States government project,
sponsored by the Advanced Research Projects
Agency (ARPA) - originally it was called the
ARPANET
• The Internet grew quickly throughout the 1980s
and 90s
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 a domain name, called a top-level
domain (TLD), indicates the type of organization:
edu
com
org
net
-
educational institution
commercial entity
non-profit organization
network-based organization
Sometimes the suffix
indicates the country:
uk
au
ca
se
-
United Kingdom
Australia
Canada
Sweden
New TLDs have
recently been added:
biz, info, tv, name
Domain Names
• A domain name can have several parts
• 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
• Looking up the owner of a domain name:
 `Who-IS: http://www.internic.net/whois.html
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
Outline
Computer Processing
Hardware Components
Networks
The Java Programming Language
Program Development
Object-Oriented Programming
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
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
 Similar to how a book is broken into chapters,
paragraphs, sentences, and words. This serves as an
organizational structuring mechanism.
• These terms will be explored in detail throughout
the course
• A Java application always contains a method
called main
• See Lincoln.java (page 27)
Java Program Structure
//
comments about the class
public class MyProgram
{
class header
class body
Comments can be placed almost anywhere
}
Java Program Structure
//
comments about the class
public class MyProgram
{
//
comments about the method
public static void main (String[] args)
{
method body
}
}
method header
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, 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 he or she
chose (such as println)
• Often we use special identifiers called reserved
words that already have a predefined meaning in
the language; a reserved represents the core of
the Java language
• A reserved word cannot be used in any other way
Reserved Words
• The Java reserved words:
abstract
assert
boolean
break
byte
case
catch
char
class
const
continue
default
do
double
else
enum
extends
false
final
finally
float
for
goto
if
implements
import
instanceof
int
interface
long
native
new
null
package
private
protected
public
return
short
static
strictfp
super
switch
synchronized
this
throw
throws
transient
true
try
void
volatile
while
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 many ways
• Programs should be formatted to enhance
readability, using consistent indentation
• See Lincoln2.java (page 33)
• See Lincoln3.java (page 34)
Outline
Computer Processing
Hardware Components
Networks
The Java Programming Language
Program Development
Object-Oriented Programming
Program Development
• The mechanics of developing a program include
several activities
 writing the program in a specific programming language
(such as Java)
 translating the program into a form that the computer can
execute
 investigating and fixing various types of errors that can
occur
• Software tools can be used to help with all parts of
this process
• Integrated Development Environments (IDEs) like
Eclipse combine all of these activites
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 to read and write programs
Programming Languages
• Each type of CPU executes only a particular
machine language
• A program must be translated into machine
language before it can be executed
• 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 source
code
Java
compiler
Java
bytecode
Bytecode
interpreter
Bytecode
compiler
Machine
code
Development Environments
• There are many programs that support the
development of Java software, including:







Sun Java Development Kit (JDK)
Sun NetBeans
IBM Eclipse
Borland JBuilder
MetroWerks CodeWarrior
BlueJ
jGRASP
• 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
Edit and
save program
errors
errors
Compile program
Execute program and
evaluate results
Outline
Computer Processing
Hardware Components
Networks
The Java Programming Language
Program Development
Object-Oriented Programming
Problem Solving
• The purpose of writing a program is to solve a
problem
• Solving a problem consists of multiple activities:
 Understand the problem
 Design a solution
 Consider alternatives and refine the solution
 Implement the solution
 Test the solution
• These activities are not purely linear – they
overlap and interact
Problem Solving
• The key to designing a solution is breaking it down
into manageable pieces
• When writing software, we design separate pieces
that are responsible for certain parts of the
solution
• An object-oriented approach lends itself to this
kind of solution decomposition
• We will dissect our solutions into pieces called
objects and classes
Object-Oriented Programming
• Java is an object-oriented programming language
• As the term implies, an object is a fundamental
entity in a Java program
• Objects can be used effectively to represent realworld entities
• For instance, an object might represent a
particular employee in a company
• Each employee object handles the processing and
data management related to that employee
Objects
• An object has:
 state - descriptive characteristics
 behaviors - what it can do (or what can be done to it)
• The state of a bank account includes its account
number and its current balance
• The behaviors associated with a bank account
include the ability to make deposits and
withdrawals
• Note that the behavior of an object might change
its state
Classes
• An object is defined by a class
• A class is the blueprint of an object
• The class uses methods to define the behaviors of
the object
• The class that contains the main method of a Java
program represents the entire program
• A class represents a concept, and an object
represents the embodiment of that concept
• Multiple objects can be created from the same
class
Objects and Classes
A class
(the concept)
An object
(the realization)
Bank
Account
John’s Bank Account
Balance: $5,257
Multiple objects
from the same class
Bill’s Bank Account
Balance: $1,245,069
Mary’s Bank Account
Balance: $16,833
Inheritance
• One class can be used to derive another via
inheritance
• Classes can be organized into hierarchies
Account
Charge
Account
Bank
Account
Savings
Account
Checking
Account
Summary
• Chapter 1 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
an introduction to Java
an overview of object-oriented concepts