Cpp htp5e 01

1

1
Introduction to
Computers, the
Internet and
World Wide Web
© 2006 Pearson Education, Inc. All rights reserved.

2

The chief merit of language is clearness.
— Galen

Our life is frittered away by detail…. Simplify,
simplify.
— Henry David Thoreau

He had a wonderful talent for packing thought
close, and rendering it portable.
— Thomas B. Macaulay

Man is still the most extraordinary computer of all.
— John F. Kennedy


3

OBJECTIVES
In this chapter you will learn:
 Basic hardware and software concepts.
 Basic object-technology concepts, such as classes, objects,
attributes, behaviors, encapsulation and inheritance.
 The different types of programming languages.
 Which programming languages are most widely used.
 A typical C++ program development environment.
 The history of the industry-standard object-oriented system
modeling language, the UML.
 The history of the Internet and the World Wide Web.
 To test-drive C++ applications in two popular C++
environments—GNU C++ running on Linux and Microsoft's
Visual C++® .NET running on Windows® XP.

4

1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
1.11
1.12
1.13
1.14
1.15
1.16

Introduction
What Is a Computer?
Computer Organization
Early Operating Systems
Personal, Distributed and Client/Server Computing
The Internet and the World Wide Web
Machine Languages, Assembly Languages and High-Level Languages
History of C and C++
C++ Standard Library
History of Java
FORTRAN, COBOL, Pascal and Ada
Basic, Visual Basic, Visual C++, C# and .NET
Key Software Trend: Object Technology
Typical C++ Development Environment
Notes About C++ and C++ How to Program, 5/e
Test-Driving a C++ Application

1.17

Software Engineering Case Study: Introduction to Object Technology and
the UML (Required)
Wrap-Up
Web Resources

1.18
1.19


5

1.1 Introduction
• Software
– Instructions to command computer to perform actions and
make decisions

• Hardware
• Standardized version of C++
– United States
• American National Standards Institute (ANSI)

– Worldwide
• International Organization for Standardization (ISO)

• Structured programming
• Object-oriented programming


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1.2 What Is a Computer?
• Computer
– Device capable of performing computations and making logical
decisions

• Computer programs
– Sets of instructions that control computer’s processing of data
– Written by people called computer programmers

• Hardware
– Various devices comprising computer
• Keyboard, screen, mouse, disks, memory, CD-ROM, processing
units, etc.


7

1.3 Computer Organization
• Six logical units of computer
– Input unit
• “Receiving” section
• Obtains information from input devices
– Keyboard, mouse, microphone, scanner, networks, etc.

– Output unit
• “Shipping” section
• Places information processed by computer on output devices
– Screen, printer, networks, etc.
– Information can also be used to control other devices


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1.3 Computer Organization (Cont.)
• Six logical units of computer (Cont.)
– Memory unit
• Rapid access, relatively low capacity “warehouse” section
• Retains information from input unit
– Immediately available for processing
• Retains processed information
– Until placed on output devices
• Often called memory or primary memory

– Arithmetic and logic unit (ALU)
• “Manufacturing” section
• Performs arithmetic calculations and logic decisions


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1.3 Computer Organization (Cont.)
• Six logical units of computer (Cont.)
– Central processing unit (CPU)
• “Administrative” section
• Coordinates and supervises other sections of computer

– Secondary storage unit
• Long-term, high-capacity “warehouse” section
• Stores inactive programs or data
• Secondary storage devices
– Hard drives, CDs, DVDs
• Slower to access than primary memory
• Less expensive per unit than primary memory


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1.4 Early Operating Systems
• Early computers
– Single-user batch processing
• Only one job or task at a time
• Process data in groups (batches)
– Decks of punched cards
• Users had to wait hours or days for results

• Operating systems
– Software systems that manage transitions between jobs
– Increased throughput
• Amount of work computers can process


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1.4 Early Operating Systems (Cont.)
• Multiprogramming
– Many jobs or tasks sharing computer’s resources
– “Simultaneous” operation of many jobs

• Timesharing
– Special case of multiprogramming
– Users access computer through terminals
• Devices with keyboards and screens
• Dozens, even hundreds of users

– Computer use is shared among all users
• Performs small portion of one user’s job, then moves on to service next user

– Advantage
• User receives almost immediate responses to requests


1.5 Personal, Distributed and
Client/Server Computing

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• Personal computers
– Popularized in 1977 by Apple Computer
• Economical enough for individual

– Ligitimized in 1981 by IBM Personal Computer
– “Standalone” units

• Computer networks
– Connected over telephone lines
– Local area networks (LANs)

• Distributed computing
– Organization’s computing distributed over networks


1.5 Personal, Distributed and
Client/Server Computing (Cont.)

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• Workstations
– Provide enormous capabilities

• Client/server computing
– File servers
• Offer common store of programs and data

– Client computers
• Access file servers across network

• UNIX, Linux, Mac OS X and Microsoft’s Window-based
systems support these capabilities


14

1.6 The Internet and the World Wide Web
• Internet
– Global network of computers
• Initiated almost four decades ago

– Accessible by computers worldwide today

• World Wide Web
– Allows computer users to locate and view multimediabased documents
– Internet has become one of the world’s premier
communication mechanisms


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1.7 Machine Languages, Assembly Languages
and High-Level Languages
• Three types of computer languages
– Machine language
• Only language computer directly understands
– “Natural language” of computer
– Defined by hardware design
• Generally consist of strings of numbers
– Ultimately 0s and 1s
• Instruct computers to perform elementary operations
• Cumbersome for humans
• Example
– +1300042774
+1400593419
+1200274027

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and High-Level Languages (Cont.)
• Three types of computer languages (Cont.)
– Assembly language
• English-like abbreviations representing elementary computer
operations
• Clearer to humans
• Incomprehensible to computers
– Convert to machine language by translator programs
(assemblers)
• Example
– load
add
store

basepay
overpay
grosspay


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and High-Level Languages (Cont.)
• Three types of computer languages (Cont.)
– High-level languages
• Similar to everyday English
– Uses common mathematical notations
• Single statements accomplish substantial tasks
• Converted to machine language by translator programs (compilers)
• Interpreter programs
– Directly execute high-level language programs
– Execute more slowly than the compiled program
• Example
– grossPay = basePay + overTimePay


18

1.8 History of C and C++
• History of C
– Evolved from BCPL and B
• Developed by Dennis Ritchie (Bell Laboratories)

– Development language of UNIX
– Hardware independent
• Can write portable programs

– ANSI and ISO standard for C published in 1990
• ANSI/ISO 9899: 1990


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Portability Tip 1.1
Because C is a standardized, hardwareindependent, widely available language,
applications written in C often can be run
with little or no modification on a wide
range of computer systems.


20

1.8 History of C and C++ (Cont.)
• History of C++
– Extension of C
• Developed by Bjarne Stroustrup (Bell Laboratories) in early 1980s

– Provides new features to “spruce up” C
– Provides capabilities for object-oriented programming
• Objects: reusable software components
– Model items in the real world
• Object-oriented programs
– Easier to understand, correct and modify


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1.9 C++ Standard Library
• C++ programs
– Built from pieces called classes and functions

• C++ Standard Library
– Rich collections of existing classes and functions
• Reusable in new applications


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Software Engineering Observation 1.1
Use a “building-block” approach to create
programs. Avoid reinventing the wheel. Use
existing pieces wherever possible. Called software
reuse, this practice is central to object-oriented
programming.


23

When programming in C++, you typically will
use the following building blocks: Classes and
functions from the C++ Standard Library,
classes and functions you and your colleagues
create and classes and functions from various
popular third-party libraries.


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Performance Tip 1.1
Using C++ Standard Library functions and
classes instead of writing your own versions can
improve program performance, because they are
written carefully to perform efficiently. This
technique also shortens program development
time.


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Portability Tip 1.2
Using C++ Standard Library functions and
classes instead of writing your own improves
program portability, because they are included
in every C++ implementation.


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1.10 History of Java
• Java
– Originally for intelligent consumer-electronic devices
• Designed by Sun Microsystems

– Then used for creating Web pages with dynamic content
– Now also used for:
• Develop large-scale enterprise applications
• Enhance World Wide Web server functionality
• Provide applications for consumer devices (cell phones, etc.)


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1.11 FORTRAN, COBOL, Pascal and Ada
• FORTRAN
– FORmula TRANslator
– Used in engineering applications

• COBOL
– COmmon Business Oriented Language
– Used in business software

• Pascal
– Designed to teach structured programming

• Ada
– Capable of multitasking


1.12 Basic, Visual Basic, Visual C++, C#
and .NET

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• BASIC
– Beginner’s All-Purpose Symbolic Instruction Code
– Familiarize novices with programming techniques

• .NET platform
– Provides developers with capabilities

• Visual Basic .NET
– Based on BASIC

• Visual C++
– Based on C++

• C#
– Based on C++ and Java


1.13 Key Software Trend: Object
Technology

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• Objects
– Reusable software components that model real world items
– Meaningful software units
• Time objects, paycheck objects, record objects, etc.
• Any noun can be represented as an object

– More understandable, better organized and easier to
maintain than procedural programming
– Libraries of reusable software
• MFC (Microsoft Foundation Classes)
• .NET Framework Class Library
• Rogue Wave


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Extensive class libraries of reusable software
components are available over the Internet and
the World Wide Web. Many of these libraries
are available at no charge.


1.14 Typical C++ Development
Environment

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• C++ programs normally undergo six phases
– Edit
• Programmer writes program (and stores source code on disk)

– Preprocess
• Perform certain manipulations before compilation

– Compile
• Compiler translates C++ programs into machine languages

– Link
• Link object code with missing functions and data

– Load
• Transfer executable image to memory

– Execute
• Execute the program one instruction at a time

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Fig. 1.1 | Typical C++ environment.


1.14 Typical C++ Development
Environment (Cont.)

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• Input/output
– cin
• Standard input stream
• Normally inputs from keyboard

– cout
• Standard output stream
• Normally outputs to computer screen

– cerr
• Standard error stream
• Displays error messages


34

Common Programming Error 1.1
Errors like division by zero occur as a program
runs, so they are called runtime errors or
execution-time errors. Fatal runtime errors cause
programs to terminate immediately without
having successfully performed their jobs.
Nonfatal runtime errors allow programs to run
to completion, often producing incorrect results.
[Note: On some systems, divide-by-zero is not a
fatal error. Please see your system
documentation.]


1.15 Notes About C++ and C++ How to
Program, 5/e

35

• This book is geared toward novice programmers
– Stresses programming clarity

• Portability
– C and C++ programs can run on many different computers


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Good Programming Practice 1.1
Write your C++ programs in a simple and
straightforward manner. This is sometimes
referred to as KIS (“keep it simple”). Do not
“stretch” the language by trying bizarre usages.


37

Portability Tip 1.3
Although it is possible to write portable
programs, there are many problems among
different C and C++ compilers and different
computers that can make portability difficult to
achieve. Writing programs in C and C++ does
not guarantee portability. The programmer
often will need to deal directly with compiler
and computer variations. As a group, these are
sometimes called platform variations.


38

Read the manuals for the version of C++ you are
using. Refer to these manuals frequently to be
sure you are aware of the rich collection of C++
features and that you are using them correctly.


39

Your computer and compiler are good teachers.
If after reading your C++ language manual, you
still are not sure how a feature of C++ works,
experiment using a small “test program” and see
what happens. Set your compiler options for
“maximum warnings.” Study each message that
the compiler generates and correct the programs
to eliminate the messages.


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1.16 Test-Driving a C++ Application
• Running and interacting with a C++ application
– Windows XP Command Prompt
– Linux shell


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Using the cd command
to change directories

File location of the GuessNumber application

Fig. 1.2 | Opening a Command Prompt window and changing the directory.


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Enter guess number prompt

Fig. 1.3 | Running the GuessNumber application.


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Enter first guess

Fig. 1.4 | Entering your first guess.


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Fig. 1.5 | Entering a second guess and receiving feedback.


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Fig. 1.6 | Entering additional guesses and guessing the correct number.


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Fig. 1.7 | Playing the game again.


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Fig. 1.8 | Exiting the game.


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~$ cd examples/ch01/GuessNumber/GNU_Linux
~/examples/ch01/GuessNumber/GNU_Linux$

Fig. 1.9 | Changing to the GuessNumber application’s directory after logging in to

your Linux account.


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Compile the application with
the GNU C++ compiler

~/examples/ch01/GuessNumber/GNU_Linux$ g++ GuessNumber.cpp -o GuessNumber

Fig. 1.10 | Compiling the GuessNumber application using the g++ command.


50

~/examples/ch01/GuessNumber/GNU_Linux$ ./GuessNumber
I have a number between 1 and 1000.
Can you guess my number?
Please type your first guess.
?

Fig. 1.11 | Running the GuessNumber application.


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? 500
Too high. Try again.
?

Fig. 1.12 | Entering an initial guess.


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? 500
? 250
Too low. Try again.
?

Fig. 1.13 | Entering a second guess and receiving feedback.


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Too low. Try again.
? 375
Too low. Try again.
? 437
? 406
? 391
? 383
Too low. Try again.
? 387
? 385
? 384
Excellent! You guessed the number.
Would you like to play again (y or n)?

Fig. 1.14 | Entering additional guesses and guessing the correct number.


54

Would you like to play again (y or n)? y
?

Fig. 1.15 | Playing the game again.


55

Would you like to play again (y or n)? n

Fig. 1.16 | Exiting the game.


1.17 Software Engineering Case Study:
Introduction to Object Technology and the UML
(Required)
• Object orientation

56

– A natural way of thinking about the world and computer
programs

• Unified Modeling Language (UML)
– Graphical language that uses common notation
– Allows developers to represent object-oriented designs


57

1.17 Software Engineering Case Study (Cont.)
• Objects
– Reusable software components that model real-world items
– Examples are all around you
• People, animals, cars, telephones, microwave ovens, etc.

– Have attributes
• Size, shape, color, weight, etc.

– Exhibit behaviors
• Babies cry, crawl, sleep, etc.; cars accelerate, brake, turn, etc.


58

• Object-oriented design (OOD)
– Models real-world objects in software
– Models communication among objects
– Encapsulates attributes and operations (behaviors)
• Information hiding
• Communication through well-defined interfaces

• Object-oriented language
– Programming in object oriented languages is called objectoriented programming (OOP)
– C++ is an object-oriented language
• Programmers can create user-defined types called classes
– Contain data members (attributes) and member functions
(behaviors)

59

Reuse of existing classes when building new
classes and programs saves time, money and
effort. Reuse also helps programmers build
more reliable and effective systems, because
existing classes and components often have
gone through extensive testing, debugging and
performance tuning.


60

• Object-Oriented Analysis and Design (OOAD)
– Analyze program requirements, then develop solution
– Essential for large programs
– Plan in pseudocode or UML


61

• History of the UML
– Used to approach OOAD
– Object Management Group (OMG) supervised
• Brainchild of Booch, Rumbaugh and Jacobson

– Version 1.5 is current version
• Version 2 under development

• UML
– Graphical representation scheme
– Enables developers to model object-oriented systems
– Flexible and extendible


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