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Decision making & Looping

A sequence of statements are executed until sometermination conditions satisfied.

Program loop: body of loop.

control statement -> tests certain conditions & then

directs repeated execution of statements within the bodyof loop.

Two types: Based on position of control statement.

1) Entry controlled loop: control are tested

before the start of the loop. If false body will not beexecuted.

2) Exit controlled loop: test is performed at theend of the body. i.e body of loop executed at least once.

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Entry Controlled & Exit controlled loop

True

Entry

TestCondition

Body ofThe loop

False

TestCondition

True

Body of

The loop

False

Exit

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While statement

Basic format:

while (test condition)

{

body of the loop

}

* Entry controlled loop statement.Test condition evaluated & if it is true, then body of the loop

is executed. After execution, the test condition is again

evaluated & if it is true, the body is executed again. This

Procedure is repeated until test condition becomes false, & control

transferred out of the loop. i.e body of loop may notexecuted if the condition is false at the very first attempt.

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Example

#include

void main()

{

int counter;counter =0;

while (counter < 5)

{cout

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Example

#include

void main()

{

int counter;

int sum;

sum=0; //initialize sumcounter=0;

while (counter

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The do statementGeneral form:

do

{body of the loop

}

while (test condition);

Exit controlled loop.After do statement, program executes the body of the

Loop.

At the end of the loop, the test condition in the while is

evaluated. If it is true, body of the loop is executed once

again & this process continues as long as the condition istrue. When condition becomes false, the loop will be

terminated.

Body of the loop executed at least once.

do while loop can be nested.

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Example#include

void main(){

int counter;

int sum;

sum=0; //initialize sum

counter=0;do

{

sum=sum+counter;

counter = counter+1;

} while (counter

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The for statement

The general form:

for (intilization; test condition; increment)

{Body of the loop

}

Entry controlled loop.Next statement;

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Explanation

1. The expression initial_value1 is evaluated, usually anassignment statement that sets a variable to aparticular value.

2.The expression condition is evaluated. It is typically a

relational expression.3. If condition evaluates as false (zero), the for statement

terminates and execution passes to the first statementfollowing the for statement that is the next_statement.

4. If condition evaluates as true (non zero), the subsequentC++ statements are executed. (i.e body of the loop)

5. The expression increment is executed, and executionreturns to step no. 2.

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Example

#include

void main()

{

int counter;

int sum;

sum=0; //initialize sum

for(counter=0;counter

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Additional features of for loop

1. More than one variable can be initialized.

Example: for (p=1,n=0;n

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Continued4. It is also permissible to use expressions in the

initialization & increment sections.

Eg: for (x=(m+n)/2; x>0; x=x/2)5. In for loop one or more sections can be omitted.

Eg: i) m=5;

for(;m!=50;)

{ cout

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Nesting of for loop

One for statement within another for statement.

for (i=1;i

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Jumping out of a loop

An early exit from a loop can be accomplished

by using the break statement.

When the break statement is encountered inside

a loop, the loop is immediately exited & theprogram continues with the statement

immediately following the loop.

When the loops are nested , the break would

only exit from the loop containing it.

i.E , the break will exit only a single loop.

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Exiting a loop with break

statement

while (.)

{.

If(condition)

break;

.

}

..

Exit

From

loop

do (.)

{.

If(condition)

break;

.

} while()

..

Exit

From

loop

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for

{.

If(condition)

break;

.

}

..

ExitFrom

loop

for (.)

{.

for(..)

{

If(condition)

break;

}

..

}

..

ExitFrom

inner

loop

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Skipping a part of loop

while (.)

{.

If(condition)

continue;

.

}

..

do (.)

{.

If(condition)

continue;

.

} while()

..

Skip a part of the body of the loop under certain conditions.

Using continue statement. As the name implies, causes the loop to be

continued with next iteration, after skipping rest of the body of the

loop.

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for (.)

{.

If(condition)

continue;

.

}

..

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#include

#include

#include

//Sine of an angle upto given accuracy i.e |term|>accr;

angle=angle*pi/180;term=angle;sum=angle;

while(fabs(term)>accr)

{term=-term*angle*angle/((2*i)*(2*i+1));

sum=sum+term;

i++;

}cout

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#include

#include

#include

//Cosine of a number upto given accuracy

void main(){

int i=0;const double pi=22.0/7;

float sum,angle,term,accr;clrscr();

coutangle>>accr;

angle=angle*pi/180; term=1;sum=1;

while(fabs(term)>accr)

{

term=-term*angle*angle/((2*i+1)*(2*i+2));

sum=sum+term;

i++;}

cout

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#include

#include

#define true 1

#define false 0

//To check whetherthe number is prime or not

void main(){

int n,i,prime;clrscr();

coutn;

if(n==1)

cout

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#include

#include

//Generating prime numbers below the given limit

void main()

{

int n,i,prime,j;clrscr();coutn;

for(i=1;i

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#include

#include

#define true 1

#define false 0

// Generate prime Fibonacci numbersvoid main()

{

int j,prime,num,i,f1,f2,fib;

clrscr();

coutnum;

cout

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{

prime = true;

if(f1%j==0)

{

prime = false;

break;}

}

if(prime==true)

cout

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#include

#include

#define true 1#define false 0

//Generating prime numbers below the given limit

void main(){

int n,i,prime,j;

clrscr();coutn;

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for(i=1;i

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#include

#include

//Find average of m numbers until negative number is typed using

type castingvoid main()

{

int m;

float sum,x,avg;

clrscr();cout