while:- It is a repeated structure statement
which repeats a statement given as long as the condition is true.
while(condition)
statement1;
statement1
is executed till the condition is true.
example:
int i = 1;
while (i <= 20)
{
cout<< i << “\t”;
++i;
}
Output: 1 2 3......... 20
do while:- Like while statement it repeats a
statement given as long as the condition is satisfied unlike in while statement
the condition is checked at the end of the structure.
do
{
statement1;
}
while(condition);
statement1 is executed till the
condition is true. Here while statement contains a semicolon.
example:
int i = 1;
do
{
cout<< i << “\t”;
++i;
} while(i <= 20);
Output: 1 2 3......... 20
for:- It is a repeated structure which can
repeat a statement as long as the given condition is satisfied.
for(statement1;
condition; statement2)
statement3;
where
statement1 initialises control variable, condition is used to check whether
statement written after loop can be repeated or not , statement2 is used to
modify the control variable. Statement3 is a simple statement (having only one
statement) or compound statement (a set of statements written within braces {}
) which can be repeated as long as condition is true or satisfied.
example:
for(i = 1; i <= 20; i++)
{
cout<< i << “\t”;
++i;
}
Output: 1 2 3......... 20
Nested loop:- When one repeated structure is written within one or
more such repeated structures then the entire structure is known as nested
loop.
example:
int i = 1;
while(i <= 3)
{
int j = 1;
while(j <= 2)
{
cout<< i << “;” << j << “ ”;
j++;
}
i++;
}
Output: 1;1 1;2
2;1 2;2 3;1
3;2
Lets have some examples.
Q. Write a program to read two positive integers and
check whether they are coprime or not.
#include<iostream>
void
main()
{
int a, b, p, q;
cout<< “Enter two numbers”;
cin>> a >> b;
p = a;
q = b;
while (b != 0)
{
int r = a % b;
a = b;
b = r;
}
if(a == 1)
cout<< p <<
“ and ”<< q << “are coprime”;
else
cout<< p <<
“ and ”<< q << “are not coprime”;
}
Q.Write a program to read a
list of numbers terminated by -1 and determine positive average of positive numbers.
#include<iostream>
void
main()
{
int a, s = 0, i = 0;
cout<< “Enter a list of
numbers terminated by -1”;
do
{
cin>> a;
if(a < 0)
continue;
s = s + a;
++i;
}while(a != -1);
cout<< “No of +ve numbers
read”<< i << endl << “Avg=”<< s/float(i);
}
Q. Write a program to
display odd factors of a positive integer.
#include<iostream>
#include<iomanip.h>
void
main()
{
int a, n;
cout<< “Enter the value of
a”;
cin>> a;
for(i = 1; i <= n; i += 2)
if(a % i == 0)
cout<<setw(5)<<i;
}
Q. Write a program to
print following pattern.
54321
5432
543
54
5
#include<iostream>
#include<iomanip.h>
void main()
{
int i, j;
for (i = 1;i <= 5;i++)
{
for (j = 5; j >= i; j--)
cout<< setw(5) << j;
cout<< endl;
}
}
Q. Write a program to display factorial of a
given positive integer.
Q. Write a program to read a positive integer and
check whether it is prime or not.
Q. Write a program to display binary equivalent
of a given decimal no.
Q. Write a program to find sum of the digits and
reverse of an n digit number.
Q. Write a program to display followin pattern.
1
212
32123
4321234
543212345
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