Whole c++ lectures ITM1 Th

DUHOK PLOYTECHNIC
UNIVERSITY
C++
(lectures)
2015-2016
Prepared By:
Zhiyan A.younis

Computer is a device capable of performing
computations and making logical decisions at speeds
faster than human beings. it is designed to follow
instructions (program). All computer systems consist
of similar hardware devices and software components.
The computer programs that run on a computer are
referred to as software(SW). While the hard
component of it is called hardware (HW).
Programming is the process of writing instructions
for a computer in a certain order to solve a
problem using computer languages..
What is a computer???
2

The CPU:
The CPUs job is to fetch instructions, follow the instructions, and produce some
result. The CPU unit consists of: the control unit and the arithmetic and logic
unit (ALU). The CU is responsible for determining where to get the next
instruction and regulating the other major components of the computer with
control signals. The ALU is designed to perform mathematical operations.
Main memory:
Commonly known as random-access memory, or RAM, the computer´s main
memory is a device that holds information. Specifically, RAM holds the
sequences of instructions in the programs that are running and the data
those programs are using.
Secondary storage:
Secondary storage is a type of memory that can hold data for long periods of
time-even when there is no power to the computer. Frequently used
programs are stored in secondary memory and loaded in to main , memory
as needed. Important information, such as word processing documents,
payroll data, and inventory figures, is saved to secondary storage as well.4

Inputs Devices:
Input is any information the computer collects from the world. The
device that collects the information and sends it to the computer
is called an input device.
Output Devices:
Output is any information the computer sends to the outside
world. Common output devices are monitors, printers and
speakers. Output sent to a monitor is called “softcopy”, while
output sent to a printer is called “hard copy”.
5

Software:
Software refers to the programs that run on a computer. There are
two general categories of software: operating system and
application software.
1-Programming Languages:
There are two categories of programming languages: low-level and high-level. A low
level language is close to the level of the computer, which means it resembles the
numeric machine language of the computer more than the natural language of
humans. The easiest languages for people to learn are high level languages. They
are called “high level” because they are closer to the level of human-readability than
computer readability.
C++ is popular not only because of its mixture of low and high-level features, but also
because of its portability. This means that a C++ program can be written on one type
of computer and then run on many other types of systems.
2- Operating system:
An operating system is a set of programs that
manages the computer´s hardware devices and
controls their processes.
6

C++ Program Development Process
(PDP):
C++ programs typically go through six phases before they can be
executed. These phases are:
1. Edit: The programmer types a C++ source program, and makes
correction, if necessary. Then file is stored in disk with extension
(.cpp).
2. Pre-Processor: Pre-processing is accomplished by the pre-
proceccor before compilation, which includes some substitution
of files and other directories to be include with the source file.
3. Compilation: Converting the source program into object-code.
4. Linking: A linker combines the original code with library
functions to produce an executable code.
5. Loading: The loader loads the program from the disk into
7

Short History about programming langueges:
1954: Fortran.
1957: Cobol.
1958: Lisp.
1964: Basic.
1970: Pascal (From Algol).
1971: C (From a language called B).
1980: C with classes (experimental version).
1983: C++ (by Bjarne Stroustrup).
1986: Objective-C (from C and Smalltalk).
1991: Java.
2000: C#.
8

Algorithm :
algorithm can be defined as a finite sequence of
effect statements to solve a problem.
Example 1: Develop an algorithm that inputs a
series of number and output their average
"Read a number".
"Add a number to anther number".
"Output a number".
10

Flowcharts
A flowchart is a graphical representation of an
algorithm
11

Draw the flowchart required to find the sum of negative numbers
among 50 numbers entered by the user.
12

Character set: In C++ language, upper case and lower
case letters are distinct and hence there are 52 letters
in all. For example bag is different from Bag which is
different from BAG.
Special Characters:
13

Identifiers: An identifier is a name given to
some program entity such as variable ,
constant, array, function, structure, or class.
A variable works as a store for values (letters,
numbers and Boolean). When we choose the name of
an identifier there are some conditions:-
1- Starting with letters or underscore symbol.
2- The length of identifiers should be less than (256)
letters.
3- The C++ language is sensitive for the case of letters
(small and capital).
14

Keywords:The keywords are also
identifiers but cannot be user defined, since they
are reserved words. All the keywords should be in
lower case letters. Reserved words cannot be
used as variable names or constant. The following
words are reserved for use as keywords:
15

Constants are identifiers that can hold values but
; their values can not be changed after they
initialized.
Constants types:
1. String Constants :“This is test program”
3.Character Constants: ‘A’, ‘a’, ‘:’, ‘?’, etc…
2. Numeric Constants:integer, floating point,
hexadecimal, and octal.
16

Example:
X+y*X-Z,
where
X=5,
Y=6,
and Z=8.
19

Assignment Operators
Ex:
x=x+5;
y=y*10;
x+=5;
y*=10;
20

Comparision and logical operators
(a) Relational operators: <, >, <= , >=
(b) Equality operators: ==, !=
(c) Logical operators: not(!), and(&&), or(||).
21

Type Conversion
int x;
float y;
x=y;
Statements:
22

STARTING WITH C++
Every C++ program has an anatomy.
Unlike human anatomy, the parts of
C++programs are not always in the
same place. Nevertheless, the parts
are there and your first step in
learning C++ is to learn what they
are.

THE PARTS OF A C++ PROGRAM
There are three main parts in c++
programs:
• Comments
• Header
• body
24

WHAT ARE COMMENTS?
Comments are used to document and explain your
codes and program logic. Comments are not
programming statements and are ignored by the
compiler, but they VERY IMPORTANT for providing
documentation and explanation for others to understand
your program(and also for yourself some days later).
There are two kinds of comments in c/c++:
1. Multi-line Comment: begins with a /* and ends with a
*/, and can span several lines .
2. End-of-line comment :begins with // and lasts till the
end of the current line.
25

HEADER
Any line started with a #, it is called a pre-processor directive. Pre-
processor reads your program before it is compiled and only
executes those lines beginning with a # symbol.
The # include directive causes the pre-processor to include the
contents of another file in the program. The word inside the
brackets, iostream.h is the name of the file that is to be included
.The iostream.h file contains code that allows a C++ program to
display output on the screen and read input from the keyboard .
The iostream file is called a header file, so it should be included at
the top of the program.
C++ provides several libraries of pre-written functions for you that
perform frequently needed operations. You access these libraries
by placing #include statements at the top of your source code file.
The most commonly used libraries are listed below. 26

HEADERS
iostream provides cin and cout
cmath provides math functions like: sin(), aqrt(),
log10()
cstdlib provides miscellaneous routines like rand()
ctime provides function for manipulating time
string allows use of the string type
vector allows use of the vector type
list allows use of the list type
27

Getting Started with C++:
The keyboard and screen I/O
instructions in C++ are:
(a): COUT/ display an object onto the
video screen:
Cout<<var.1<<var2<<…<<var.n;
(b): Cin/ It is used to read an object
from a standard input device
(keyboard):
Cin>>var.1>>var.2>>…>>var.n;
28

Constants
Write a program that reads the radius of a circle, then computes
and outputs its area.
#include<iostream.h>
void main( )
{
const float pi = 3.14;
int r; float c;
cout << “enter the radius of circle:”;
cin>>r;
cout<<endl;
c = r * r * pi;
cout << “the area of circle:” << c;
}
34

The following program computes the arethmatic
operators.
void main( )
{
int a,b,sum,sub,mul,div;
cout << “enter any two numbers<<endl;
cin>> a>>b;
sum=a+b;
sub=a-b;
mul=a*b;
div=a/b;
cout<<”a=”<<a<<”b=”<<b<<”sum=”<<sum<<endl;
cout<<”sub=”<<sub<<endl;
cout<<”mul=”<<mul<<endl;
cout<<”div=”<<div<<endl;
}
35

The following program computes different division
operators.
void main( )
{
int x, y, z, r ;
x= 7 / 2;
cout << "x=" << x <<endl;
y=17/(-3);
cout << "y="<< y <<endl;
z=-17/3;
cout << "z="<< z <<endl;
r=-17/(-3);
cout << "r="<< r <<endl;
}
36

The modulus operator “%” is used with integer
operands (int, short, long,unsigned). It can’t be used
with float or double operands.
void main( )
{
int y1, y2;
y1 = 8 % 3;
y2 = -17 % 3;
cout << "y1="<< y1 <<endl;
cout << "y2="<< y2 <<endl;
}
37

Example 2:
State the order of evaluation for the following expression:
Z = P * R % Q + W / X – Y;
38

Write C++ program to perform the above equation:
void main( )
{
int Z, P, R, Q, W, X, Y;
cout << "enter P:"; cin >> P;
cout << "enter R:"; cin >> R;
cout << "enter Q:"; cin >> Q;
cout << "enter W:"; cin >> W;
cout << "enter X:"; cin >> X;
cout << "enter Y:"; cin >> Y;
Z= P * R % Q + W / X - Y;
cout << "the result="<< Z;
}
39

Example:
Write the following equation as a C++ expression and
state the order of
evaluation of the binary operators:
Solution:
f = sqrt ((sin(x) – pow(x,5)) / (log(x) + x/4))
Order of evaluation:
41

Manipulator Functions:
Write C++ program to convert a base of a number:
void main( )
{
int value;
cout << "enter number:"; cin >> value;
cout << "Decimal base=”<<dec<<value<<endl;
cout << "Hexadecimal base=”<<hex<<value<<endl;
cout << "Octa base=”<<oct<<value<<endl;
}
43

Manipulator Functions:
Setw: It is used to specify the minimum number of
character positions on the O/P field a variable will
consume: setw(int w)
Write C++ program to use tab:
#include<iomanip.h>
void main( void)
{
int a,b;
a=200;
b=300;
cout<<a<<’t’<<b<<endl;
}
44

SELECTION STATEMENTS
• The Single If Statement
• The if-else Statement
• The nested if statement
• The case-switch Statement
45

SELECTION STATEMENTS
The Single If Statement Structure
46

The Single Block If Statement Structure :
48

49

50

The If/else Statement Structure:
51

Example 1:
cin >> value;
if ( value >= 0 )
cout << “positive”;
else
cout << “negative”;
52

Example 2:
cin >> num1 >> num2;
if ( num1 > num2 )
cout << num1;
else
cout << num2;
53

1. THE SWITCH SELECTION STATEMENT (SELECTOR):
General Form of Switch Selection statement:
switch ( selector )
{
case label1 : statement1 ; break;
:
case label-n : statement-n ; break;
default : statement-e ; break;
}
60

Example 1:
switch (value)
{
case 0: cout << “grade is A”;
break;
case 1: cout<< “grade is B”;
break;
case 2: coucout << “grade is C”;
break;
default: cout << “grade is X”;
break;
}
61

Notice that the break statement tells where to stop
execution.
Example:
void main()
{int mark; cout<<”enter mark :”; cin>>mark;
switch (mark/10)
{
case 5:cout<<”passn”;break;
case 6:cout<<”mediumn”;break;
--
--
case 10:cout<<”excellentn”;break;
default:cout<<”fail!n”;break;
}
62

Write C++ program to read two integer numbers, and read the
operation to perform on these numbers:
void main( )
{
int a, b;
char x;
cout << “Enter two numbers n”;
cin >> a >> b;
cout << “+ for addition n”;
cout << “- for subtraction n”;
cout << “* for multiplication n”;
cout << “/ for division n”;
cout << “enter your choice n”;
cin >> x;
63

switch ( x )
{
case ‘+’: cout << a + b;
break;
case ‘-’: cout << a - b;
break;
case ‘*’: cout << a * b;
break;
case ‘/’: cout << a / b;
break;
default: break;
}
}
64

2. NESTED SWITCH SELECTION STATEMENT:
General Form of Nested Switch Selection statement:
switch ( selector1 )
{case label1 : statement1 ; break;
case label3 : switch ( selector2 )
{ case label1 : statement1 ; break;
: }
case label-n : statement-n ; break;
default : statement-e ; break;
}
65

Write C++ program to read integer number, and print the name of
the computerized department:
void main( )
{
int i,j;
cout << “Enter the number for the department name n”;
cin >> i>>j;
switch (i)
{
case 1: cout << “Software Engineering Department”; break;
case 2: cout << “Control and computers Department”; break;
case 3: cout << “Computer Sciences Department”;
cout<<”Enter the no. of branch”;
66

switch(j)
{
case 1: cout << “Software”; break;
case 2: cout << “Information system”; break;
case 3: cout << “Security”;
case 4: cout << “AI”;
}
default: cout << “Invalid day number”; break;
}
}
67

3. CONDITIONAL STATEMENT:
General Form of Conditional statement:
( condition ? True : False )
Example 1:
cin >> value;
cout << (value >= 0 ? “positive” : “negative” );
Example 2:
cin >> x >> y;
cout << ( x < y ? -1 : (x == y ? 0 : 1) );
68

Write C++ program to read integer number, and print if its
even or odd:
void main( )
{
int value;
cout << “Enter the number n”;
cin >> value;
cout<<(value%2==0?”even”:”odd”);
}
69

LOOP STATEMENTS:
General Form of For statement:
for ( initialization ; continuation condition ; update )
statement1 ;
for ( initialization ; continuation condition ; update )
{
statement1 ;
statement2 ;
}
70

LOOP STATEMENTS:
Example 1:
for ( i = 0; i < 10; i ++ )
cout << i;
Output:
0 1 2 3 4 5 6 7 8 9
Example 2:
for ( i = 0; i < 10; i += 2 )
cout << i;
Output:
even numbers only
0 2 4 6 8
71

LOOP STATEMENTS:
Example 3:
for ( i = 1; i < 10; i += 2 )
cout << i;
Output:
odd numbers only
1 3 5 7 9
72

LOOP STATEMENTS:
Example 1
Write C++ program to add the numbers between 1 and
100:
void main( )
{
int sum = 0;
for ( int i = 1; i <= 100; i ++ )
sum = sum + i;
cout << “sum is: “ << sum;
}
73

LOOP STATEMENTS:
Write C++ program to add the numbers between 1 and
100:
void main( )
{
int sum = 0;
for ( int i = 1; i <= 100; i ++ )
sum = sum + i;
cout << “sum is: “ << sum;
}
74

LOOP STATEMENTS:
Write C++ program to find the factorial of n (using for
statement ):
n! = n * n-1 * n-2 * n-3 * … * 2 * 1
void main( )
{
int n, f = 1;
cout << “enter positive number: “;
cin >> n;
for ( int i = 2; i <= n; i ++ )
f = f * i;
cout << “factorial is: “ << f;
}
75

LOOP STATEMENTS:
Write C++ program to the result of the following:
void main( )
{
int sum = 0;
for ( int i = 1; i <= 20; i ++ )
sum = sum + ( i * i );
cout << “The sum is: “ << sum;
}
76

LOOP STATEMENTS:
Example 4
Write C++ program to read 10 integer numbers, and find
the sum of positive number only:
void main( )
{
int num, sum = 0;
for ( int i = 1; i <= 10; i ++ )
{
cout << “enter your number: “;
cin >> num;
if ( num > 0 ) sum = sum + num;
}
cout << “The sum is: “ << sum;
}
77

LOOP STATEMENTS:
Example 5
Write C++ program to print the following series: 1, 2, 4, 8,
16, 32, 64
void main( )
{
int x;
for ( x = 1; x < 65; x *= 2 )
cout << x <<” “;
}
78

LOOP STATEMENTS:
Example 6
Write C++ program to print the following:
void main( )
{
int x;
for ( x = 1; x < 7; ++ x )
cout << x <<”t“ << 11 – x << endl;
}
1 10
2 9
3 8
4 7
5 6
6 5
79

LOOP STATEMENTS:
Example 9
Write C++ program to print the following figure:
+
+ +
+ + +
+ + + +
+ + + + +
+ + + + + +
+ + + + + + +
+ + + + + + + +
+ + + + + + + + +
+ + + + + + + + + +
80

LOOP STATEMENTS:
General Form of While statement:
• while (condition )
statement1 ;
• while (condition )
{ statement1 ;
statement2 ;
:
statement-n ; }
81

i = 0;
while ( i < 10 )
{
cout << i;
i ++;
}
Output:
0 1 2 3 4 5 6 7 8 9
i=10
LOOP STATEMENTS:
82

Example 2:
i = 0;
while ( i < 10 )
{
cout << i;
i += 2;
}
LOOP STATEMENTS:
Output: print even numbers only
that are between(0,10)
0 2 4 6 8
83

Example 3:
i = 1;
while ( i < 10 )
{
cout << i;
i += 2;
}
LOOP STATEMENTS:
Output: odd numbers only
1 3 5 7 9
i=11
84

void main( )
{int i = 1;
int sum = 0;
while ( i <= 99 )
{
sum = sum + i;
i = i + 2;
}
cout << “sum is: “ << sum << endl;
}
WRITE C++ PROGRAM TO FIND THE SUMMATION OF THE FOLLOWING
SERIES:
SUM = 1 + 3 + 5 + 7 + … + 99
IN OTHER WORDS: FIND THE SUMMATION OF THE ODD NUMBERS,
BETWEEN 0 AND 100)
85

void main( )
{
int num , cubenum ;
cout << “Enter positive number n”;
cin >> num;
while ( num > 0 )
{
cubenum = num * num * num;
cout << “cube number is :” << cubenum << endl;}
WRITE C++ PROGRAM TO FIND THE CUB OF A NUMBER, WHILE IT IS
POSITIVE:
86

void main( )
{int i = 1, n ,sum = 0;
cout << “enter positive number”;
cin >> n;
while ( i <= n )
{sum += i * i ;
i++;
}cout << “sum is: “ << sum << endl;
}
WRITE C++ PROGRAM TO FIND THE SUMMATION OF THE FOLLOWING
SERIES:
87

void main( )
{int mark, i, sum = 0;
float av = 0;
i = 1;
while ( i <= 8 )
{cout << “enter mark: “;
cin >> mark;
sum = sum + mark;
i++;
}cout << “sum is: “ << sum << endl;
av = sum / 8;
cout << “average is: “ << av;
}
WRITE C++ PROGRAM TO FIND THE SUMMATION OF
STUDENT’S MARKS, AND IT’S AVERAGE, ASSUME THE
STUDENT HAVE 8 MARKS:
88

do
statement1 ;
while (condition );
do
{
statement1 ;
statement2 ;
:
statement-n ;
}
while (condition );
DO / WHILE STATEMENT:
89

Example 1:
i = 0;
do
{
cout << i;
i ++;
}
while ( i < 10 )
Output:
0 1 2 3 4 5 6 7 8 9
i=10
90

Example 2:
i = 0;
do
{
cout << i;
i += 2;
}
while ( i < 10 )
Output:
even numbers only
0 2 4 6 8
i=10
91

void main( )
{int accept = 1;
int x, low = 50, high = 70;
do
{cout << “enter number: “;
cin >> x;
if ( x >= low && x <= high )
accept =1;
else
accept = 0;}
while ( ! accept );}
WRITE C++ PROGRAM TO VALID INPUT CHECKING, THAT
ACCEPT THE NUMBERS BETWEEN 50 ... 70 ONLY:
92

void main( )
{ int mark, i, sum = 0;
float av = 0;
i = 1;
do { cout << “enter mark: “;
cin >> mark;
sum = sum + mark;
i++;}
while ( i <= 8 )
cout << “sum is: “ << sum << endl;
av = sum / 8;
cout << “average is: “ << av; }
Write C++ program to find the summation of students
marks, and its average , assume the student have 8
marks:
93

void main( )
{int n, f = 1;
cout << “enter positive number: “;
cin >> n;
do
{f = f * n;
n - -;}
while ( n > 1 );
cout << “factorial is: “ << f;}
N! = N * N-1 * N-2 * N-3 * … * 2 * 1
Write c++ program to find the factorial of N:
94

BREAK CONTROL STATEMENT
Example 1:
for ( i = 1; i < 100; i ++ )
{
cout << i;
if ( i == 10 ) break;
}
Output:
1 2 3 4 5 6 7 8 9 10
the break statement causes a loop to terminate early. Sometimes
it’s necessary to stop a loop before it goes through all its
iterations. When it is encountered, the loop stops and the
program jumps to the statement immediately following the loop.
95

BREAK CONTROL STATEMENTS
Example 2:
for ( i = 1; i < 10; ++ i )
for ( j = 1; j < 20; ++ j )
{
cout << i * j << endl;
if ( j == 10 ) break;
}
In a nested loop, the break statement only
interrupts the loop it is placed in.
96

BREAK CONTROL STATEMENTS
Write C++ program to check if zero or negative value
found:
void main( )
{ int value , I ; i=0;
while (i<=10) {
cout<<”enter a number n”;
cin>>value; if (value<=0) {
cout<<”Zero or negative value found
n”;
The continue statement causes a loop to stop its current
iteration and begin the next one!
97

CONTINUE CONTROL STATEMENTS:
Example 1:
do
{
cin >> x;
cin >> n;
if ( n < 1 ) continue;
cout << x;
-- n;
}
while ( n < 1 ); 98

ARRAYS:
An array is a consecutive group of homogeneous memory
locations.
Each element (location) can be referred to using the array name
along with an integer that denotes the relative position of that
element within the array. The data items grouped in an array
can be simple types like int or float, or can be user-defined
types like structures and objects. There are array of one or two
dimensions…
Array of One Dimension:
It is a single variable specifies each array element. The
declaration of
one dimensional arrays is:
data-type Array-name [ size ];99

Examples: int age [10]; int num [30];
float degree[5]; char a [15];
The item in an array are called elements (in contrast to the items
in a structure which are called members). The elements in an
array are of the same type only the values vary.
100

ARRAY OF ONE DIMENSION:
Initializing Array Elements
The first element of array age:
age [0] = 18;
- The last element of array age:
age [9] = 19;
- All elements of array age:
age [9] = { 18, 17, 18 ,18 ,19, 20 ,17, 18 ,19,19 };
- int x [ ] = { 12, 3, 5, 0, 11, 7, 30, 100, 22 };
- int y [10] = { 8, 10, 13, 15, 0, 1, 17, 22};
101

Write C++ program to display 2nd and 5th
elements of array distance:
void main( )
{ double distance[ ] = { 23.14, 70.52, 104.08,
468.78, 6.28};
cout << “2nd element is: “ << distance[1] << endl;
cout << “5th element is: “ << distance[4];
}
102

Write C++ program to read 5 numbers and print it in
reverse order:
void main( )
{ int a [5]; cout << "Enter 5 numbers n";
for ( int i =0; i <5; i++ )
{ cout << i << “: “;
cin >> a [ i ];
cout << “n”;
} cout << “The reverse order is: n”;
for ( i =4; i >=0; i - - )
cout << i << “: “ << a [ i ] << endl; } 103

Write C++ program, to find the summation of array
elements:
void main ( )
{ int const L = 10; int a [L]; int sum = 0;
cout << "enter 10 numbers n";
for ( int i =0; i <L; i++ )
{cout << “enter value “ << i << “: “;
cin >> a [ i ];
sum += a [ i ];
}
cout << "sum is: " << sum << endl;
104

Write C++ program, to find the minimum value in
array of 8 numbers:
void main ( )
{ int n = 8;
int a [ ] = { 18, 25, 36, 44, 12, 60, 75, 89 };
int min = a [ 0 ];
for ( int i = 0; i < n; i++ )
if ( a [ i ] < min ) min = a [ i ];
cout << "The minimum number in array is: "
<<min; }
105

ARRAY OF TWO DIMENSION:
Examples:
int a [10] [10];
int num [3] [4];
Arrays can have higher dimension. There can be arrays of two
dimension which is array of arrays. It is accessed with two index.
Also there can be arrays of dimension higher than two.
General Form of 2D-Array:
data-type Array-name [ Row-size ] [ Col-size ];
106

ARRAY OF TWO DIMENSION:
Initializing 2D-Array Elements:
- The first element of array age:
a [2] [3] = { {1, 2, 3} , {4, 5, 6} };
107

Write C++ program, to read 15 numbers, 5 numbers per row, the
print them:
void main ( )
{int a [ 3 ] [ 5 ]; int i , j;
for ( i = 0 ; i < 3; i++ )
for ( j = 0 ; j < 5; j++ )
cin >> a [ i ] [ j ];
for ( i = 0 ; i < 3; i++ )
{for ( j = 0 ; j < 5; j++ )
cout << a [ i ] [ j ];
cout << endl;
} } 108

Structures are typically used to group several data items
together to form a single entity. It is a collection of
variables used to group variables into a single record.
Thus a structure (the keyword struct is used in C++) is
used. Keyword struct is a data-type, like the following
C++ data-types ( int, float, char, etc... ). This is unlike
the array, which all the variables must be the same
type. The data items in a structure are called the
members of the structure.
General Form of Structure:
struct struct-name
{
variables …
}; 110

For example:
Struct time
{ int hour;
Int minute;
Int second;
};
Its important to note that the structure declaration not
define a variable. It simply tells the compiler what a
time structure is made of. In essence, it creates a new
data type named time. You can define variables of this
type with simple definition statements, for example:
Time x; int a;
111

Accessing structure members
The dot operator (.) allows you to access structure members in a
program.
Examples: x.hour= 4; // assingment
cin>> y.minute; //reading
cout<<z.hour<<z.minute<<z.second; //printing
comparing structure variables
you cannot perform comparison operation directly on structure
variables. For example, assume that circle1 and circle2 are circle
structure variables. The following statement will cause an error.
If (circle1 == circle2)// error!
In order to compare two structures, you must compare the
individual members, as shown in the following code.
If ( circle1.radius == circle2.radius && circle1.diameter ==
circle2.diameter && circle1.area == circle2.area) then 112

Initializing a structure
The members of a structure variable may be initialized with starting values when the
structure variable is defined. For example:
Struct GeoInfo
{ char cityName[30];
Char state[3];
Long population;
Int distance;
};
GeoInfo location= {“ Asheville”,”nc”,50000,28};
You do not have to provide initializers for all the members of a structure variable.
For example:
GeoInfo location = {“tampa”};
GeoInfo location = {“tampa”,”GA”};
If you leave a structure member uninitialized, you must leave all the members that
follow it uninitialized as well:
GeoInfo location = {“tampa”,”GA”, ,90};//illegal!!!
113

Example: write a program to find the radius and the area of a
circle if you have the diameter (use struture).
#include <iostream.h>
#include <math.h>
Struct circle
{ double radius; double diameter; double area; };
const double pi= 3.14159;
Void main()
{ circle c;
Cout<<”enter diameter: “;cin >> c.diameter; c.radius= c.
diameter/2;
c.area = pi * pow (c. radius, 2.0)
cout<<” the radius @ the area of the circle are :n”;
cout << “radius : “<<c.radius<<endl;
cout <<” area : “ << c.area << endl; }
114

write a program to read and print the following information (student-name, mark [5], group) for (5) student and find
the average for each student.
Struct student
{ char name[20]; int mark[5]; char group; float average };
Void main()
{ student s[5]; int s1,i,j; For (i =0; i<5 ; i++)
{ s1=0; Cout<< “enter student name : “;
Cin >>s[i].name;
For (j =0; j<5 ; j++)
{ Cout<< “n enter student mark : “;
Cin >>s[i].mark[j];
s1=s1+ s[i].mark[j]; }
s[i].average = s1/5;
Cout<< “n enter student group“ ;
cin>>s[i].group; }
//printing information
For (i =0; i<5 ; i++)
{ Cout<< “n student name : “<<s [i].name; Cout<< “n student marks : “;
For (int j =0; j<5 ; j++)
{ cout << s[i].mark[j]<<”tt”;}
Cout<< “n student group“ ;<< s[i].group;
Cout<< “n student average“ ;<< s[i].average; } }
115

A pointer is a variable which holds the memory address of another
variable. The pointer has the following advantages:
1. It allows passing variables, arrays, functions, strings and structures as
function arguments.
2. A pointer allows returning structured variables from functions.
3. It provides functions which can modify their calling arguments.
4. It supports dynamic allocation and deallocation of memory segments.
5. With the help of a pointer, variables can be swapped without physically
moving them.
6. It allow to establish links between data elements or objects for
somecomplex data structures such as linked lists, stacks, queues, binary
trees,tries and graphs.
7. A pointer improves the efficiency of certain routines.
In C++ pointers are distinct such as integer, float, character, etc. A
pointer
variable consists of two parts, namely, (i) the pointer operator and (ii)
the 117

Pointer Operator:
A pointer operator can be represented by a combination of (*) with
a
variable, for example int *ptr; where ptr is a pointer variable which
holds theaddress of an integer data type.
General Form of Pointer:
Data_type *pointer_variable;
Example: int x, y; int *ptr1, *ptr2;
Address Operator:
An address operator can be represented by a combination of &
with a
pointer variable. For example, if a pointer variable is an integer
type and also declared (&) with the pointer variable, then it
means that the variable is of type “address of”. For example
m=&ptr;. Note that the pointer operator & is an operator that
returns the address of the variable following it. 118

Note:
Notice the difference between the reference and
dereference operators:
& is the reference operator and can be read as
"address of"
* is the dereference operator and can be read
as "value pointed by"
Thus, they have complementary (or opposite)
meanings. A variable referenced with & can be
dereferences with *.
119

Examples:
(1) Ptr1 = &x; The memory address of variable x is assigned to
the pointer variable ptr1.
(2) Y=*prt1; The contents of the pointer variable ptr1 is assigned
to the variable y, not the memory address.
(3) Ptr1=&x; The address of the ptr1 is assigned to the pointer
variable ptr2. The contents Ptr2=ptr1; of both ptr1 and ptr2 will
be the same as these two pointer variables hold the same
address.
120

Example: write a program to store the address of a
variable in a pointer.
Void main()
{ int x= 25; int* ptr;
ptr = &x; //store the address of x in ptr
Cout<<”the value in x is : “<< x <<endl;
cout<<” the address of x is “ << ptr <<endl; }
121

Example: write a program to read the radius of a circle
from keyboard then calculate its area and print it (use
pointer)
# include <iostream.h>
Void main()
{ double r; double *p;
P=&r;
Cout<<”enter the radius:”;
Cin>>*p;
*p= *p * *p *3.14;
Cout<<”the area =”<<*p;
}
122

write a program to read a number from keyboard then
calculate its factorial and store it in the same location
in the memory , finally print it (use pointer)
Void main()
{ int i,a,no;
No=1; int* p;
P=&a;
Cin>>*p;
For(i=1;i<= *p ; i++)
{ no=no*i; }
*p=no;
cout<<”the factorial = “<<*p; } 123

A PROGRAM TO DISPLAY THE CONTENT OF POINTERS
USING AN ARRAY OF POINTERS
void main(void)
{
Char *ptr[3];
Ptr[0]=”Ahmed”;
Ptr[1]=”Reem”;
Ptr[2]=”Ali”;
Cout<<”contents of pointer 1 =”<<ptr[0]<<endl;
}
contents of pointer 1 = Ahmed
contents of pointer 2 = Reem
contents of pointer 3 = Ali
124

Functions:
A function is a set of statements designed to accomplish
a particular task . Experience has shown that the best
way to develop and maintain a large program is to
construct it from smaller pieces or (modules). Modules
in C++ are called functions . Functions are very useful
to read, write, debug and modify complex programs.
They can also be easily incorporated in the main
program. In C++,the main() itself is a function that
means the main function is invoking the other
functions to perform various tasks.
125

Defining a Function
A function definition has a name, parentheses pair containing zero ormore parameters
and a body. For each parameter, there should be a corresponding declaration that
occurs before the body. Any parameter not declared is taken to be an integer by
default. The general format of the function definition is :
General Form of Function:
return-type function-name ( parameters-list )
{
(body of function)
statement1 ;
statement2 ;
:
statement-n ;
(return something)
}
126

The type of the function may be int, float, char, etc. It may be
declared as type (void), which informs the compiler not to the
calling program. For example:
Void function_name (---)
Int function_name (---)
Any variable declared in the body of a function is said to be local
to that function. Other variables which are not declared either
as arguments or in the function body are considered “global” to
the function and must be definedexternally. For example
Void square (int a, int b) → a,b are the formal arguments.
Float output (void) → function without formal arguments
127

Example 1:
void printmessage ( )
{
cout << “University of Technology”;
}
void main ( )
{ printmessage( ); }
Example 2:
int max (int a, int b)
{ int c;
if (a > b) c = a;
else c = b;
return (c);
}
void main ( )
{ cout << max (5, 6);} 128

Return Statement:
The keyword return is used to terminate function and return a
value to its caller. The return statement may also be used to
exit a function without returning a value. The return
statement may or may not include an expression. Its
general syntax is:
Return;
Return (expression);
The return statements terminate the execution of the function
and pass the control back to the calling environment.
129

Example 1
Write C++ program to calculate the squared value of a number passed from
main function. Use this function in a program to calculate the squares of
numbers from 1 to 10:
int square ( int y )
{ int z;
z = y * y;
return ( z );
}
void main( )
{
int x;
for ( x=1; x <= 10; x++ )
cout << square ( x ) << endl;
}
130

Example 2
Write C++ program using function to calculate the average of two numbers entered by the user in the
main program:
float aver (int x1, int x2)
{ float z;
z = ( x1 + x2) / 2.0;
return ( z);
}
void main( )
{ float x; int num1,num2;
cout << "Enter 2 positive number n";
cin >> num1 >> num2;
x = aver (num1, num2);
cout << x;
}
131

Example 4
Write a function to find the largest integer among three integers entered by the user in the main
function.
int max(int y1, int y2, int y3)
{ int big; big=y1;
if (y2>big) big=y2;
if (y3>big) big=y3;
return (big);
}
void main( )
{ int largest,x1,x2,x3;
cout<<"Enter 3 integer numbers:";
cin>>x1>>x2>>x3;
largest=max(x1,x2,x3);
cout<<largest;
}
132

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