chapter01 (1).ppt

 2000 Deitel & Associates, Inc. All rights reserved.
Chapter 1 – Introduction to Computers
and C++ Programming
Outline
1.1 Introduction
1.2 What is a Computer?
1.3 Computer Organization
1.4 Evolution of Operating Systems
1.5 Personal Computing, Distributed Computing and Client/Server Computing
1.6 Machine Languages, Assembly Languages, and High-level Languages
1.7 History of C and C++
1.8 C++ Standard Library
1.9 Java and Java How to Program
1.10 Other High-level Languages
1.11 Structured Programming
1.12 The Key Software Trend: Object Technology
1.13 Basics of a Typical C++ Environment
1.14 Hardware Trends
1.15 History of the Internet
1.16 History of the World Wide Web
1.17 General Notes About C++ and This Book
1.18 Introduction to C++ Programming
1.19 A Simple Program: Printing a Line of Text
1.20 Another Simple Program: Adding Two Integers
1.21 Memory Concepts
1.22 Arithmetic
1.23 Decision Making: Equality and Relational Operators
1.24 Thinking About Objects: Introduction to Object Technology and the Unified Modeling
Language

1.1 Introduction
– In this course you will learn
– C and C++
– Structured programming and object oriented
programming

1.2 What is a Computer?
• A computer is a device capable of performing
computations and making logical decisions
• Computers process data under the control of sets of
instructions called computer programs
• Hardware – various devices comprising a computer
– Keyboard, screen, mouse, disks, memory, CD-ROM, and
processing units
• Software – programs that run a computer

1.3 Computer Organization
• Six logical units in every computer:
1. Input unit
• obtains information from input devices (keyboard, mouse)
2. Output unit
• outputs information (to screen, to printer, to control other devices)
3. Memory unit
• rapid access, low capacity, stores input information
4. Arithmetic and logic unit (ALU)
• performs arithmetic calculations and logic decisions
5. Central processing unit (CPU)
• supervises and coordinates the other sections of the computer
6. Secondary storage unit
• cheap, long-term, high-capacity storage, stores inactive programs

1.4 Evolution of Operating Systems
• Batch processing
– do only one job or task at a time
• Operating systems
– manage transitions between jobs
– increased throughput - amount of work computers process
• Multiprogramming
– many jobs or tasks sharing the computer resources
• Timesharing
– runs a small portion of one user’s job then moves on to service the
next user

1.5 Personal Computing, Distributed
Computing, and Client/Server Computing
• Personal computers
– economical enough for individual
• Distributed computing
– organizations computing is distributed over networks
• client/server computing
– sharing of information, across computer networks,
between file servers and clients (personal computers)

1.6 Machine Languages, Assembly
Languages, and High-level Languages
• Three types of programming languages
1. Machine languages
– strings of numbers giving machine specific instructions
– Example:
+1300042774
+1400593419
+1200274027
2. Assembly languages
– English-like abbreviations representing elementary computer
operations (translated via assemblers)
– Example:
LOAD BASEPAY
ADD OVERPAY
STORE GROSSPAY

1.6 Machine Languages, Assembly
Languages, and High-level Languages (II)
3. High-level languages
– similar to everyday English and use mathematical notations
(translated via compilers)
– Example:
grossPay = basePay + overTimePay

1.7 History of C and C++
• C++ evolved from C, which evolved from two
previous programming languages, BCPL and B
• ANSI C established worldwide standards for C
programming
• C++ “spruces up” C and provides capabilities for
object-oriented programming
– objects - reuseable software components, model things in the real
world
– Object-oriented programs are easy to understand, correct and
modify

1.8 C++ Standard Library
• C++ programs consist of pieces called classes and
functions
• There are rich collections of existing classes and
functions in the C++ standard library available for
all programmers to use

1.9 Java and Java How to Program
• Java used to
– create Web pages with dynamic and interactive content
– develop large-scale enterprise applications
– enhance the functionality of Web servers
– provide applications for consumer devices (such as cell phones,
pagers and personal digital assistants)
• Java How to Program
– closely followed the development of Java by Sun
– teaches first-year programming students the essentials of graphics,
images, animation, audio, video, database, networking,
multithreading and collaborative computing

1.10 Other High-level Languages
• A few other high-level languages have achieved broad
acceptance
• FORTRAN
– for scientific and engineering applications
• COBOL
– used to manipulate large amounts of data
• Pascal
– intended for academic use

1.11 Structured Programming
• structured programming
– a disciplined approach to writing programs
– clear, easy to test and debug, and easy to modify
• Multitasking
– specifying that many activities run in parallel

1.12 The Key Software Trend: Object
Technology
• Objects
– reusable software components that model items in the
real world
– meaningful software units
• date objects, time objects, paycheck objects, invoice objects,
audio objects, video objects, file objects, record objects, etc.
• any noun can be represented as an object
– very reusable
– more understandable, better organized, and easier to
maintain than procedural programming
– Favor modularity

1.13 Basics of a Typical C++ Environment
• Phases of C++ Programs:
1. Edit
2. Preprocess
3. Compile
4. Link
5. Load
6. Execute
Loader
Primary
Memory
Program is created in
the editor and stored
on disk.
Preprocessor program
processes the code.
Loader puts program
in memory.
CPU takes each
instruction and
executes it, possibly
storing new data
values as the program
executes.
Compiler
Compiler creates
object code and stores
it on disk.
Linker links the object
code with the libraries,
creates a.out and
stores it on disk
Editor
Preprocessor
Linker
CPU
Primary
Memory
.
.
.
.
.
.
.
.
.
.
.
.
Disk
Disk
Disk
Disk
Disk

1.14 Hardware Trends
• Every year or two the following approximately
double:
– the amount of memory they have in which to execute
programs
– the amount of secondary storage (such as disk storage)
to hold programs and data over the longer term
– their processor speeds the speed at which computers
execute their programs

1.15 History of the Internet
• The internet enables
– Quick and easy communication via e-mail
– International networking of computers
• packet switching
– Transfer digital data via small packets
– Allows multiple users to send and receive data simultaneously
• No centralized control
– if one part of the Internet fails, other parts can still operate
• bandwidth
– the information carrying capacity of communications lines

1.16 History of the World Wide Web
• World Wide Web
– users can locate and view multimedia-based documents
on almost any subject
– makes information instantly and conveniently
accessible worldwide
– makes it possible for individuals and small businesses
to get worldwide exposure
– is changing the way business is done

1.17 General Notes About C++
and This Book
• Book is geared for novice programmers
• programming clarity is stressed
• C and C++ are portable languages
– programs written in C and C++ can run on many different
computers

1.18 Introduction to C++ Programming
• The C++ language facilitates a structured and
disciplined approach to computer program design
• Following are several examples that illustrate
many important features of C++. Each example is
analyzed one statement at a time.

Outline
1.19 Printing a line of
text
1 // Fig. 1.2: fig01_02.cpp
2 // A first program in C++
3 #include <iostream>
4
5 int main()
6 {
7 std::cout << "Welcome to C++!n";
8
9 return 0; // indicate that program ended successfully
10 }
Welcome to C++!
preprocessor directive
Message to the C++ preprocessor
Lines beginning with # are preprocessor directives
#include <iostream> tells the preprocessor to
include the contents of the file <iostream>, which
includes input/output operations (such as printing to
the screen).
Comments
Written between /* and */ or following a //
Improve program readability and do not cause the
computer to perform any action
C++ programs contain one or more functions, exactly
one of which must be main
Parenthesis used to indicate a function
int means that main "returns" an integer value.
More in Chapter 3.
Left brace { begins the body of every function
and a right brace } ends it
Prints the string of characters contained between the
quotation marks.
The entire line, including std::cout, the <<
operator, the string "Welcome to C++!n" and
the semicolon (;), is called a statement.
All statements must end with a semicolon.
return is one a way to exit a
function.
return 0, in this case, means that
the program terminated normally.

1.19 A Simple Program:
Printing a Line of Text
• std::cout
– standard output stream object
– “connected” to the screen
– we need the std:: to specify what "namespace" cout belongs to
• we shall remove this prefix with using statements
• <<
– stream insertion operator
– value to the right of the operator (right operand) inserted into
output stream (which is connected to the screen)
std::cout << " Welcome to C++!n"
•
– escape character
– indicates that a “special” character is to be output

1.19 A Simple Program:
Printing a Line of Text (II)
• There are multiple ways to print text
– Following are more examples
Escape Sequence Description
n Newline. Position the screen cursor to the
beginning of the next line.
t Horizontal tab. Move the screen cursor to the next
tab stop.
r Carriage return. Position the screen cursor to the
beginning of the current line; do not advance to the
next line.
a Alert. Sound the system bell.
Backslash. Used to print a backslash character.
" Double quote. Used to print a double quote
character.

Outline
1. Load <iostream>
2. main
2.1 Print "Welcome"
2.2 Print "to C++!"
2.3 newline
2.4 exit (return 0)
Welcome to C++!
1 // Fig. 1.4: fig01_04.cpp
2 // Printing a line with multiple statements
4
5 int main()
6 {
7 std::cout << "Welcome ";
8 std::cout << "to C++!n";
9
11 }
Unless new line 'n' is specified, the text continues
on the same line.

Outline
1. Load <iostream>
2. main
2.1 Print "Welcome"
2.2 newline
2.3 Print "to"
2.4 newline
2.5 newline
2.6 Print "C++!"
2.7 newline
2.8 exit (return 0)
1 // Fig. 1.5: fig01_05.cpp
2 // Printing multiple lines with a single statement
4
5 int main()
6 {
7 std::cout << "WelcomentonnC++!n";
8
10 }
Welcome
to
C++!
Multiple lines can be printed with one
statement

1.20 Another Simple Program:
Adding Two Integers
• Variables
– location in memory where a value can be stored for use by a
program
– must be declared with a name and a data type before they can be
used
– Must appear before variable is used
– Some common data types are:
• int - integer numbers
• char - characters
• double - floating point numbers
– Example: int myVariable;
• Declares a variable named myVariable of type int
Example: int variable1, variable2;
• Declares two variables, each of type int

1.20 Another Simple Program:
Adding Two Integers (II)
• >> (stream extraction operator)
– When used with std::cin, waits for user to input a value and
stores the value in the variable to the right of the operator.
– user types number, then presses the Enter (Return) key to send the
data to the computer
– Example:
int myVariable;
std::cin >> myVariable;
• waits for user input, then stores input in myVariable
• = (assignment operator )
– assigns value to a variable
– binary operator (has two operands)
sum = variable1 + variable2;
Addition operator

Outline
1. Load <iostream>
2. main
2.1 Initialize variables
integer1, integer2, and
sum
2.2 Print "Enter first
integer"
2.2.1 Get input
2.3 Print "Enter second
integer"
2.3.1 Get input
2.4 Add variables and put
result into sum
2.5 Print "Sum is"
2.5.1 Output sum
2.6 exit (return 0)
Program Output
1 // Fig. 1.6: fig01_06.cpp
2 // Addition program
4
5 int main()
6 {
7 int integer1, integer2, sum; // declaration
8
9 std::cout << "Enter first integern"; // prompt
10 std::cin >> integer1; // read an integer
11 std::cout << "Enter second integern"; // prompt
12 std::cin >> integer2; // read an integer
13 sum = integer1 + integer2; // assignment of sum
14 std::cout << "Sum is " << sum << std::endl; // print sum
15
17 }
Enter first integer
45
Enter second integer
72
Sum is 117
Notice how std::cin is used to get user
input.
Variables can be output using std::cout << variableName
std::endl flushes the buffer and
prints a newline.

1.21 Memory Concepts
• Variable names correspond to locations in the
computer's memory.
– Every variable has a name, a type, a size and a value.
– Whenever a new value is placed into a variable, it replaces the
previous value - it is destroyed
– reading variables from memory does not change them
• A visual representation
integer1 45

1.22 Arithmetic
• Arithmetic calculations are used in most programs
– special notes:
– use * for multiplication and / for division
– integer division truncates remainder
7 / 5 evaluates to 1
– modulus operator returns the remainder
7 % 5 evaluates to 2
• Operator precedence
– some arithmetic operators act before others (i.e., multiplication
before addition)
• be sure to use parenthesis when needed
– Example: Find the average of three variables a, b and c
• do not use: a + b + c / 3
• use: (a + b + c ) / 3

1.22 Arithmetic (II)
• Arithmetic operators:
• Rules of operator precedence:
C++ operation Arithmetic
operator
Algebraic
expression
C++ expression
Addition + f + 7 f + 7
Subtraction - p – c p - c
Multiplication * bm b * m
Division / x / y x / y
Modulus % r mod s r % s
Operator(s) Operation(s) Order of evaluation (precedence)
() Parentheses Evaluated first. If the parentheses are nested, the
expression in the innermost pair is evaluated first. If
there are several pairs of parentheses “on the same level”
(i.e., not nested), they are evaluated left to right.
*, /, or % Multiplication Division
Modulus
Evaluated second. If there are several, they re
evaluated left to right.
+ or - Addition
Subtraction
Evaluated last. If there are several, they are
evaluated left to right.

1.23 Decision Making: Equality and
Relational Operators
• if structure - decision based on truth or falsity of
condition. If condition met execute, otherwise ignore.
• Equality and relational operators:
• These operators all have lower precedence than arithmetic
operators
Standard algebraic equality
operator or
relational operator
C++ equality
or relational
operator
Example
of C++
condition
Meaning of
C++ condition
Relational operators
> > x > y x is greater than y
< < x < y x is less than y
>= x >= y x is greater than or equal to
y
<= x <= y x is less than or equal to y
Equality operators
= == x == y x is equal to y
!= x != y x is not equal to y
<
_
>
_
=

1.23 Decision Making: Equality and
Relational Operators (II)
• using statements
– eliminate the need to use the std:: prefix
– allow us to write cout instead of std::cout
– at the top of the program write
using std::cout;
using std::cin;
using std::endl;
to use those functions without writing std::

Outline
1. Load <iostream>
2. main
2.1 Initialize num1 and
num2
2.1.1 Input data
2.2 if statements
1 // Fig. 1.14: fig01_14.cpp
2 // Using if statements, relational
3 // operators, and equality operators
5
6 using std::cout; // program uses cout
7 using std::cin; // program uses cin
8 using std::endl; // program uses endl
9
10 int main()
11 {
12 int num1, num2;
13
14 cout << "Enter two integers, and I will tell youn"
15 << "the relationships they satisfy: ";
16 cin >> num1 >> num2; // read two integers
17
18 if ( num1 == num2 )
19 cout << num1 << " is equal to " << num2 << endl;
20
21 if ( num1 != num2 )
22 cout << num1 << " is not equal to " << num2 << endl;
23
24 if ( num1 < num2 )
25 cout << num1 << " is less than " << num2 << endl;
26
27 if ( num1 > num2 )
28 cout << num1 << " is greater than " << num2 << endl;
29
30 if ( num1 <= num2 )
31 cout << num1 << " is less than or equal to "
32 << num2 << endl;
33
The if statements test the truth
of the condition. If it is true,
body of if statement is
executed. If not, body is
skipped.
To include multiple statements
in a body, delineate them with
braces {}
Enter two integers, and I will tell you
the relationships they satisfy: 3 7
3 is not equal to 7
3 is less than 7
3 is less than or equal to 7
Notice the using statements

Outline
2.3 exit (return 0)
Program Output
34 if ( num1 >= num2 )
35 cout << num1 << " is greater than or equal to "
36 << num2 << endl;
37
39 }
3 is not equal to 7
3 is less than 7
22 is not equal to 12
22 is greater than 12
22 is greater than or equal to 12
7 is equal to 7
7 is greater than or equal to 7

1.24 Thinking About Objects: Introduction to
Object Technology and the Unified Modeling
Language
• Object orientation
– natural way to think about world and writing computer programs
– Attributes - properties of objects
• size, shape, color, weight, etc.
– Behaviors - actions
• a ball rolls, bounces, inflates and deflates
• objects can perform actions as well
– inheritance
• new classes of objects absorb characteristics of existing classes
– information hiding
• objects usually do not know how other objects are implemented
• Abstraction - view the big picture
– See a photograph rather than a group of colored dots
– Think in terms of houses, not bricks

1.24 Thinking About Objects: Introduction to
Object Technology and the Unified Modeling
Language (II)
• class - unit of programming
– "blueprint" of the objects
• objects are created from the class
– contain functions
• implement behaviors
– contain data
• implement attributes
– Classes are reusable
• Unified Modeling Language (UML)
– used to model object-oriented systems and aid with their design
– complex, feature-rich graphical language

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