Loop control in c++

Debre Tabor University
Department of Mathematics
Loop control statments
2016
By: Wudneh Tilahun Mengist

Out lines of the presentation
Introduction
Iteration/About loop
The for loop
The While loop
The Do…While loop
Nested Loop
User defined functions
Prepared by: Wudneh Tilahun, Debre Tabor
University-2016

INTRODUCTION
Generally a program executes its statements from beginning to
the end, but all programs don't follow this. This presentation will
tell us in detail about the program control statements.
STATEMENTS
Statements are the instructions given to the computer to perform
any kind of data movements, be it making decisions or repeating
actions. They form the smallest executable unit of the program.
They are terminated by a semicolon(;). The different types of
statements are:-
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STATEMENT FLOW CONTROL
In a program, statements may be executed sequentially , selectively
or iteratively:-
Sequence:- This is the default flow of the statements and also
known as sequence construct and it also means that
the statements are being executed sequentially.
Selection:- The selection construct means that the execution of
the statements depends on a condition-test, if the
condition is true then the statements would be
executed else they would be skipped. An else-if
statement is a good example of selection statement.
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Iteration:-  The iteration means repetition of a certain set
of statements based on a certain condition-test.
Looping statements can be used to perform the
repetition of a certain set of statements.
 Iteration statements in c++ allows a certain
number of instructions to be performed
repeatedly until a certain condition becomes
false or for a fixed number of times.
 Iteration statements are also called loops or
looping statements.
There are three C++ repetition statements:
 The For Statement or loop
 The While statement or loop
 The do…while statement or loopPrepared by: Wudneh Tilahun, Debre Tabor
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Elemnts that control a loop
Every loop has its elements that control and govern the execution.
Generally, a loop has 4 elements that have different purposes. These
elements are as given below:-
1. Initialization Expression(s):
Before entering the loop the initialization expression(s) initializes
the loop control variables with their first values.
2. Test Expression:
The test expression is that expression whosetruth value decides
whether the loop-body will be executed or not. If the value is true
then the body gets executed else it gets terminated.
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3. Update expression(s): The update expression(s) change the
value(s) of loop variable(s). The update expression execute at the
end of the loop.
4. The Body-of-the-loop: The statements that are to be
executed form the body-of-the-loop.
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THE FOR LOOP
The for loop is the easiest to understand of all because all its loop-
control elements are gathered in one place i.e. at the top. Its syntax is:-
For(initialization expression(s);test—expression; update expression)
body-of-the-loop;
Example of for loop
#include<iostream.h>
int main()
{
int i;
for(i=1;i<=10;i++)
cout<<“n”<<i;
return 0;
}
Condition
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 Firstly, initialization expression is executed i.e., i=1 which
gives the first value 1 to variable i.
 Then, the test-expression is executed i.e., i<=10 which results
into true i.e., 1.
 Since, the test expression is true, the body-of-the-loop i.e.,
cout<<“n”<<i is executed which prints the current value of i
on the next line.
 After executing the loop-body, the update expression i.e., i++
is executed which increments the value of i.
 After the update expression is executed, the test-expression is
again evaluated. If it is true the sequence is repeated from
step no. 3, otherwise the loop terminates.
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ForExpr
Action
true false
ForInit
PostExpr
Evaluated once
at the beginning
of the for
statements's
execution
The ForExpr is
evaluated at the
start of each
iteration of the
loop
If ForExpr is
true, Action is
executed
After the Action
has completed,
the
PostExpression
is evaluated
If ForExpr is
false, program
execution
continues with
next statement
After evaluating the
PostExpression, the next
iteration of the loop starts
Prepared by: Wudneh Tilahun,
Debre Tabor University-2016

Example
for (int i = 0; i < 3; i++)
{
cout << "i is " << i << endl;
}
cout << "all done" << endl;
i 0

Example
for (int i = 0; i < 3; i++)
{
}
i is 0
i 0

Example
for (int i = 0; i < 3; i++)
{
}
i is 0
i 1

Example
for (int i = 0; i < 3; i++)
{
}
i 1

Example
for (int i = 0; i < 3; i++)
{
}
i is 0
i is 1
i 1

Example
for (int i = 0; i < 3; i++)
{
}
i is 0
i is 1
i 2

Example
for (int i = 0; i < 3; i++)
{
}
i is 0
i is 1
i is 2
i 2

Example
for (int i = 0; i < 3; i++)
{
}
i is 0
i is 1
i is 2
i 3

Example
for (int i = 0; i < 3; i++)
{
}
i is 0
i is 1
i is 2
all done
i 3

Let us see how it’s work
int main()
{
return 0;
}
Example:- write a c++ program which evaluate
the sum of the first +ve n integer.
Alterna

int main()
{
int n, i=1;
cout << "Enter a positive integer : ";
cin >> n;
for(long sum=0; i <= n;i++)
sum += i;
cout << "The sum of the first " << n << " integers is " << sum;
return 0;
}
Example:- write a c++ program which evaluate
the sum of the first +ve n integer.
Alterna

Example- let n=10
i --
sum 0
for(long sum=0; i <= 10;i++)
sum += i;
cout << "The sum of the first " << n
<< " integers is " << sum;

Example- let n=10
i 1
sum 0
sum += i;

Example- let n=10
sum += i;
i 1
sum 0
1<=10 is True

Example- let n=10
sum += i;
i 1
sum 0
Sum=sum+i=0+1=1

Example- let n=10
sum += i;
i 1
sum 1

Example- let n=10
sum += i;
i 1
sum 1
i=i+1=1+1=2

Example- let n=10
sum += i;
i 2
sum 1

Example- let n=10
sum += i;
i 2
sum 1
2<=10 is True

Example- let n=10
sum += i;
i 2
sum 1
Sum=sum+i=1+2=3

Example- let n=10
sum += i;
i 2
sum 3

Example- let n=10
sum += i;
i 3
sum 3

Example- let n=10
sum += i;
i 3
sum 6

Example- let n=10
sum += i;
i 4
sum 6

Example- let n=10
sum += i;
i 4
sum 10

Example- let n=10
sum += i;
i 5
sum 10

Example- let n=10
sum += i;
i 5
sum 15

Example- let n=10
sum += i;
i 6
sum 15

Example- let n=10
sum += i;
i 6
sum 21

Example- let n=10
sum += i;
i 7
sum 21

Example- let n=10
sum += i;
i 7
sum 28

Example- let n=10
sum += i;
i 8
sum 28

Example- let n=10
sum += i;
i 8
sum 36

Example- let n=10
sum += i;
i 9
sum 36

Example- let n=10
sum += i;
i 9
sum 45

Example- let n=10
sum += i;
i 10
sum 45

Example- let n=10
sum += i;
i 10
sum 55

Example- let n=10
sum += i;
i 11
sum 55

Example- let n=10
sum += i;
i 11
sum 55
11<=10 is False
The for loop terminated and
go to the next statement.

Example- let n=10
sum += i;
i 11
sum 55
Output
The sum of the first 10 integers is 55

THE WHILE LOOP
• The second loop provided by c++ is the while loop. It is an
entry controlled loop. The syntax for a while loop is:-
while (expression)
loop-body
• Where the loop may contain a single statement, a compound
statement or an empty statement.
• The loop iterates while the expression is true.
• When the expression becomes false, the program control
terminates the loop.
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• In a while loop, a variable should be initialized before
the loop as uninitialized variables cannot be used in the
loop.
• The loop variable should be updated inside the body-of-
the-loop.
• Following example explains the working of a while loop;
which is a c++ program which calculates the factorial of
a positive integer.
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int main()
{
int i,n;
long fact=1;
cout<<“Enter a positive integer”;
cin>>n;
i=1;
while(i<=n)
{
fact=fact*i;
i=i++;
}
cout<<“The factorial of the num.=“<<fact;
return 0;
}

Example- let n=10
while(i<=10)
{
fact=fact*i;
i=i++;
}
i --
fact --

Example- let n=10
while(i<=10)
{
fact=fact*i;
i=i++;
}
i 1
fact 1

Example- let n=10
i 1
fact 1
1<=10 is True
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 1
fact 1
fact=1*1=1
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 1
fact 1
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 1
fact 1
i=i+1=1+1=2
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 2
fact 1
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 2
fact 1
while(i<=10)
{
fact=fact*i;
i=i++;
}
2<=10 is True

Example- let n=10
i 2
fact 1
while(i<=10)
{
fact=fact*i;
i=i++;
}
fact=1*2=2

Example- let n=10
i 2
fact 2
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 3
fact 2
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 3
fact 6
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 4
fact 6
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 4
fact 24
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 5
fact 24
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 5
fact 120
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 6
fact 120
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 6
fact 720
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 7
fact 720
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 7
fact 5040
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 8
fact 5040
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 8
fact 40320
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 9
fact 40320
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 9
fact 362880
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 10
fact 362880
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 10
fact 3628800
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 11
fact 3628800
while(i<=10)
{
fact=fact*i;
i=i++;
}

Example- let n=10
i 11
fact 3628800
while(i<=10)
{
fact=fact*i;
i=i++;
}
11<=10 is False
The for loop terminated and
go to the next statement.

Example- let n=10
i 11
fact 3628800
while(i<=10)
{
fact=fact*i;
i=i++;
}
Output
The factorial of the num.=3628800

While Semantics
Expression
Action
true false
Expression is
evaluated at the
start of each
iteration of the
loop
If Expression is
true, Action is
executed If Expression is
false, program
execution
continues w ith
next statement

Computing an Average
int main()
{
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
cout<<"Enter the numbers to be calculated"<<endl;
while (numberProcessed < listSize)
{
double value;
cin >> value;
sum += value;
numberProcessed++;
}
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
return 0;
Let us see how it works

Computing an Average
int listSize = 4;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
numberProcessed++;
}

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
Suppose input contains: 1 5 3 1 6
listSize 4

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
4listSize
0

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
4listSize
0
0

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
0
0
--

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
0
0
1

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
0
0
1
1

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
0
1
1
1

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
1
1
1

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
1
1
--

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
1
1
5

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
1
1
5
6

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
1
6
5
2

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
2
6
5
6

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
2
6
--
2

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
2
6
3
2

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
2
6
3
9

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
2
9
3
3

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
3
9
3
3

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
3
9
--
3

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
3
9
1
3

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
3
9
1
10

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
value
4listSize
3
10
1
4

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
4listSize
3
10
average 2.5
4

Execution Trace
int listSize = 4;
double sum = 0;
double value;
cin >> value;
sum += value;
numberProcessed++;
}
numberProcessed
sum
average
4listSize
3
10
2.5
4

Example : while
int a,b,sum;
cout << “This program will return the ”;
cout << “summation of integers from a to b.nn”;
cout << “Input two integers a and b:”;
cin >> a >> b;
while (a <= b)
{
sum += a;
a++;
}
cout << “The sum is ” << sum << endl;
sum = 0;
sum = sum + a;
Don’t forget to set
sum = 0;
Prepared by: Wudneh Tilahun, Debre
Tabor University-2016

THE DO-WHILE LOOP
Unlike the for and while loop do-while loop is an exit controlled loop
i.e., it evaluates the test-expression at the bottom of the loop after
the body-of-the-loop. This means that the do-while loop always
executes at least once. The syntax for do-while loop is:-
do
{
statement;
}
while(test-expression)
The brackets { } are not necessary when there is only one statement in
the loop-body.
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An example for do-while loop is:-
int i=1,n=10002;
do
{
cout<<n;
n++;
i++;
}
while(i==1);
In the above example the test expression is never true but still
every time the loop is executed the loop would execute only once
and print “10002”.
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do-while
Condition
Statement
list
T
F
do
{
Statement list
} while (Condition);
string ans = “n”;
while (ans != “Y”)
{
cout << “Would you marry me?”;
cin >> ans;
}
cout << “Great!!”;
; is required
do
{
cout << “Would you marry me?”;
cin >> ans;
} while (ans != “Y”);
cout << “Great!!”;

Example 1: do-while
int i;
....
do
{
cout << “Please input a number between ”
<< “10 and 20:”;
cin >> i;
} while (i < 10 || i > 20);
......

Primality Test
A prime number is a positive integer that cannot be
factorized, i.e., no numbers other that 1 and itself
can divide it.
is 893 a prime?
Is (893 % 2 == 0) ?
Is (893 % 3 == 0) ?
Is (893 % 4 == 0) ?
Is (893 % 5 == 0) ?
Is (893 % 6 == 0) ?
.
.
.
Is (893 % 892 == 0) ?
We can write a loop
to test these.

Example: Silly Primality Test
int main()
{
long int p,r,i=2;
cout << “Enter a positive integer:";
cin >> p;
do
{
r = p % i;
i++;
}
while (i < p && r != 0);
if (i == p)
cout << " p is a prime number.";
else
{
cout << "p is not a prime number.";
cout << "The least factor is " << --i;
}
return 0;
}

NESTED LOOPS
C++ allows its users to use a number of loops inside a single loop,
hence it means that c++ allows the use of nested loops. A user can
use nested loops according to his own requirement. The following
example explains the use of nested loops:-
for(i=1;i<=4;i++)
{
cout<<“n”;
for(j=1;j<=i;j++)
cout<<“*”;
}
In the above program the inner loop will execute for i number of
times and i has values 1,2,3,4.
Left as Reading Assignment!!!!
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The output of the above program segment would be:-
*
**
***
****
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Nested loops (loop in loop)
cin >> a >> b;
for (int i = 0; i < a; i++)
{
for (int j=0; j<b; j++)
{
cout << “*”;
}
cout << endl;
}
***
***
***
***
b
a

Nested loops (2)
int a,b;
cin >> a >> b;
for (int i = 0; i < a; i++)
{
{
if (j > i)
break;
cout << “*”;
}
cout << endl;
}
*
**
***
****
b
a

Nested loops (3) *
**
***
****
b
a
int a,b;
cin >> a >> b;
for (int i = 0; i < a; i++)
{ for (int j=0; j<b && j < i; j++)
{
cout << “*”;
}
cout << endl;
}
j <= i;
if (j > i) break;

Nested loops (4)
int a,b;
cin >> a >> b;
for (int i = 0; i < a; i++)
{
{
if (j < i)
cout << “ ”;
else
cout << “*”;
}
cout << endl;
}
*************
************
***********
**********
b
a
=

Nested loops (5)
int a,i,j;
cin >> a;
for (i = 0; i < a; i++) {
for (j=0; j<a; j++) {
if (j < a-i)
cout << " ";
else cout << "*";
}
for (j=0; j<a; j++) {
if (j > i) break;
cout << "*";
}
cout << endl;
}
*
***
*****
*******
*********
***********

User Defined functions
 Standard (Predefined) Functions
 User-Defined Functions
 Value-Returning Functions
 The return Statement
 Function Prototype
 Flow of Execution

Top-Down Structured Design with Functions
Recall two types of functions
 Value returning function
 computes a single value
 returns value to calling code
 uses return command
 Void function (procedure)
 called as a statement
 executes some task
 This chapter focuses on the value returningPrepared by: Wudneh Tilahun,

Function definition …
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• A function in C++ language is a block of code that
performs a specific task.
A function definition has the following syntax:
<type> <function name>(<parameter list>)
{
<local declarations>
<sequence of statements>
return <value>
}
User defined function
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Advantages of Using Functions
1. To help make the program more
understandable
2. To modularize the tasks of the program
 building blocks of the program
3. Write a module once
 those lines of source code are called multiple
times in the program

Advantages of Using Functions
4. While working on one function, you can focus on
just that part of the program
 construct it,
 debug it,
 perfect it.
5. Different people can work on different functions
simultaneously.
6. If a function is needed in more than one place in
a program, or in different programs, you can
write it once and use it many times

Standard (Predefined) Functions
 Predefined functions
 Part of the C++ language
 Provided in function libraries
 Examples:
abs(x), sin(x), log(x), pow( x, n)
 These functions will return a value
 To be printed cout << sin (x);
 To be assigned y = pow (3, 4.5);
 To be used in an expression 3.14 * sqr(r)
Make sure to use the
required #include file

Value-Returning Functions
For the compiler to use a function you have
written, it must know when it finds that
function call in your source code …
1. The name of the function
2. The number of parameters, if any
3. The data type of each parameter
4. Data type of the value returned by the
function
5. The code required to do the calculation
Information provided by the
heading of the function
Information provided in the
body of the function
All the properties together
make up the definition of
the function

 Consider a function for the area of a circle:
double circleArea (double radius)
{
return 3.14159 * radius * radius;
}
 Note the
 Heading (type, name, parameters)
 The body
 The return statement

 Consider a function for the area of a circle:
float CircleArea(float r){
float Pi = 3.1415;
float Area= Pi * r * r;
return Area;}
 Note the
 Heading (type, name, parameters)
 The body
 The return statement

Parameters
 Function definition syntax:
functionType functionName (formal parameter list)
{
statements
}
 Call (invocation of the function)
cout << "Enter radius for circle area -> ";
cin >> radius;
area = circleArea (radius);
Parameters in the declaration
: formal parameters
Parameters in the call:
actual parameters

The return Statement
 A value returning statement must have a
return statement
 Else a warning from the compiler
 Also the function will actually return a "garbage"
value
 Syntax:
return expression;
 View example

Function Prototype
 Recall that the compiler must know certain
things about your function
 When it finds a function call in your source code
 Must know information in heading
 Your program must have at least the
heading of a function before it is invoked
 Usually listed before function main ( )
 View example

Flow of Control
 First statement executed in any program is
the first statement in the function main( )
 When another function called
 logical control passed to first statement in that
function’s body
 program proceeds through sequence of
statements within the function
 When last statement of function executed
 control returns to where function was called
 control given to next command after the call

How to call function ???
• A function call has the following syntax:
<function name>(<argument list>)
• A function call argument list must match in both data type
and number of parameter
• Example:- from the above function
– the function name is CircleArea and
– the argument list is radius.
so that we can call the above function as
float Area=CircleArea(radius);
University-2016

Example:-Write the program of the area of a circle?
#include <iostream.h>
#include <math.h>
float CircleArea(float r)
{
float Pi = 3.1415;
float Area= Pi * r * r;
return Area;
}
int main()
{
cout << "Enter radius: ";
float Radius;
cin >> Radius;
float Area = CircleArea(Radius);
cout << "Circle has area " << Area<<“Sqr units”;
return 0;
}
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Example:
The following example is the source code
for a function called max(). This
function takes two parameters x and y and
returns the maximum froom the two:
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int max(int x, int y)
{ // returns larger of the two given integers:
if (x < y) return y; else return x;
}
int main()
{ // tests the max() function:
int m, n;
do
{ cin >> m >> n;
cout << "tmax(" << m << "," << n << ") = " <<
max(m,n) << endl;
}
while (m != 0);
return 0;
} Prepared by: Wudneh Tilahun, Debre Tabor
University-2016

Class activity
The Factorial Function
The factorial of a positive integer n is the
number n! obtained by multiplying n by all the
positive integers less than n:
n! = (n)(n - 1) • • • (3)(2)(1)
For example, 5! = (5)(4)(3)(2)(1) = 120.
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Class activity
The Permutation Function
A permutation is an arrangement of elements
taken from a finite set. The permutation function
P(n,k) gives the number of different
permutations of any k items taken from a set of n
items. One way to compute this function is by the
formula
For example, P(5,2) =
𝟓!
𝟓−𝟐 !
=
(5)(4)3!
𝟑!
= 20.
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long fact(int n)
{ // returns n!=n*(n-1)*(n-2)*...*(2)(1)
if (n< 0)
return 0;
int f= 1;
while (n >1)
f *= n-- ;
return f;
}
int main()
{
int m;
cout<<"Enter the posertive integern";
cin>>m;
cout << "The value of "<<m<<"!="<<fact(m)<< endl;
return 0;
University-2016

long fact(int n)
{ // returns n!=n*(n-1)*(n-2)*...*(2)(1)
if (n< 0)
return 0;
int f= 1;
while (n >1)
f *= n-- ;
return f;
}
long perm(int n, int k)
{ // returns P(n,k), the number of permutations of k from n:
if (n < 0 || k < 0 || k > n)
return 0;
return fact(n)/fact(n-k);
University-2016

int main()
{
int i,j;
cout<<"Enter two numbers"<<endl;
cin>>i>>j;
if(i<j)
cout<<"invalid entry, pls try again"<<endl;
else
cout<<"The value of P("<<i<<", "<<j<<")="<<perm(i,j);
return 0;
}
University-2016

Newton-Raphson Method
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Newton-Raphson Method
#include<iomanip.h>
#include<math.h>
double f(double x)
{
return pow(x,3)-17 ;
}
double g(double x)
{
return 3*pow(x,2) ;
}
int main()
{
int i,n;
double x[100];
cout<<"enter the initial point x0n";
cin>>x[0]; Prepared by: Wudneh Tilahun, Debre Tabor
University-2016

Newton-Raphson Method cont …
cout<<"Enter the number of iteration: ";
cin>>n;
for(i=1;i<=n; i++)
{
x[i]=x[i-1]-f(x[i-1])/g(x[i-1]);
cout<<"The result of iteration number "<<i<< " is
"<<setprecision(5)<<x[i]<<endl;
}
return 0;
}
University-2016

Newton-Raphson Method updated
#include<iomanip.h>
#include<math.h>
double f(double x)
{
return log(x)-cos(x);
}
double g(double x)
{
return (1/x)+sin(x) ;
}
int main()
{
int i,n;
double x[100], er;
cout<<"enter the initial point x0n";
cin>>x[0]; Prepared by: Wudneh Tilahun, Debre Tabor
University-2016

Newton-Raphson Method updated cont …
cout<<"Enter the number of iteration: ";
cin>>n;
cout<<"enter the tolerance ERROR";
cin>>er;
for(i=1;i<=n; i++)
{
x[i]=x[i-1]-f(x[i-1])/g(x[i-1]);
cout<<"The result of iteration number "<<i<< " is
"<<setprecision(5)<<x[i]<<endl;
if(fabs(x[i]-x[i-1])<er)
break;
else
continue;
}
return 0;
}
University-2016

Practice exercises
• Write and run a program that prints the sum, difference, product,
quotient, and remainder of
two integers that are input interactively.
int main()
{ // prints the results of arithmetic operators
int m,n;
cout << "Enter two integers: ";
cin >> m >> n;
cout << "The integers are " << m << " and " << n
<< endl;
cout << "Their sum is " << (m + n) << endl;
cout << "Their difference is " << (m - n) <<
endl;
cout << "Their product is " << (m * n) << endl;
cout << "Their quotient is " << (m / n) << endl;
cout << "Their remainder is " << (m % n) <<
endl;
}
University-2016

Practice exercises
• Write a program that converts inches to centimeters. For
example, if the user enters 16.9 for a length in inches, the
output would be 42.926 cm. (One inch equals 2.54
centimeters.)
• We use two variables of type float
int main()
{ // converts inches to centimeters:
float inches,cm;
cout << "Enter length in inches: ";
cin >> inches;
cm = 2.54*inches;
cout << inches << " inches = " << cm << "
centimeters.n";
}
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Practice exercises
• Write a program that implements the quadratic formula to solve
quadratic equations.
• int main()
{ // implements the quadratic formula
double a,b,c;
cout << "Enter the coefficients:" << endl;
cout << "ta: ";
cin >> a;
cout << "tb: ";
cin >> b;
cout << "tc: ";
cin >> c;
cout << "The equation is: " << a << "*x*x + " << b
<< "*x + " << c << " = 0" << endl;
double d = b*b - 4*a*c;
double sqrtd = sqrt(d);
double x1 = (-b + sqrtd)/(2*a);
double x2 = (-b - sqrtd)/(2*a);
cout << "The solutions are:" << endl;
cout << "tx1 = " << x1 << endl;
cout << "tx2 = " << x2 << endl;
cout << "Check:" << endl;
cout << "ta*x1*x1 + b*x1 + c = " << a*x1*x1 + b*x1 + c <<
endl;
cout << "ta*x2*x2 + b*x2 + c = " << a*x2*x2 + b*x2 + c <<
endl;
}
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The End
Thank you for your attention!!
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Syntax of for Loop
• The initial statement, loop
condition, and update statement are
called for loop control statements
– initial statement usually initializes a variable
(called the for loop control, or for indexed, variable)
for (initialization; condition; update)
statement;
Back to for Loop
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Syntax of while Loop
• The loop continues to iterate until the condition
becomes true.
• The while loop tests the condition at the top of the loop
and so the statement will not execute if the condition is
initially false.
while(condition)
{
statement;
} Back to for Loop
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Syntax of do…while Loop
• The statement executes first, and then the expression is
evaluated
• To avoid an infinite loop, body must contain a statement
that makes the expression false
• The statement can be simple or compound
• Loop always iterates at least once
do
{
statement;
}
while(expression);
Back to for Loop
University-2016

Loop control in c++

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