# do-while loop

Here are two examples,

## Printing only even number

```#include<iostream.h>
#include<conio.h>

void main()
{
clrscr();
int num,even=0;

cout<<"Enter Number of limit: ";
cin>>num;
// loop execute at  least one time doesn't matter condition true or false

do
{
cout<<even<<" ";  // print even value
even = even+2; // increment value by 2
}
while(even<num); // check condition

getch();
}```
```OUTPUT:-
Enter Number of limit: 9
0 2 4 6 8```

explanation:

In the program, we have declared two variables.

`int number,even=0;`

Where, the user has been asked for input for the variable number while the variable even has been initialized.

As we know that in do-while loop, the body-of-loop execution is first, then the updation takes place and in the last the condition will be checked. so here,

So here first, the value of variable even inside the body-of-loop will be printed which is 0

then updation will take place

`even = i+2;`

means,

`even = 0+2;`

Now the value of variable even has become 2.

after this, in last condition will be checked outside the loop,

`while(even<num);`

means,

`while(2<9);`

Because here, the condition is going true, so the loop will execute again and the loop will continue to execute until the condition becomes false.

Meaning until the value of the variable even gets increased to 9, ie the value of the variable even will be 9, the loop will be terminated. such as,

2time

```even = 2+2; // 4
while(2<9);// true```

3rd time

```even = 4+2; // 6
while(4<9) //true```

4th time

```even = 6+2; // 8
while(6<9)//true```

5th

```even = 8+2; // 10
while(10<9)// false```

in 5th condition becoming false so loop will be terminate.

## a simple menu demonstration of two number operation using switch and do – while loop

```#include<iostream.h>
#include<conio.h>

void main()
{
int ch;
float num1,num2;

// creating menu wizard using do-while loop
do{

clrscr();
cout<<"Enter any two number: ";
cin>>num1>>num2;

cout<<"\nselection operation\n";
cout<<"2> Substriction"<<endl;
cout<<"3> Multiply"<<endl;
cout<<"4> Division"<<endl;
cout<<"0> Exit"<<endl;

cin>>ch;

cout<<endl;

switch(ch)
{
cout<<num1<<"+"<<num2<<" = "<<num1+num2;
getch();
break;

case 2:      cout<<"\nsubstriction are"<<endl;
cout<<num1<<"-"<<num2<<" = "<<num1-num2;
getch();
break;

case 3:      cout<<"\nmultiply are"<<endl;
cout<<num1<<"x"<<num2<<" = "<<num1*num2;
getch();
break;

case 4:      cout<<"\ndivision are"<<endl;
cout<<num1<<"/"<<num2<<" = "<<num1/num2;
getch();
break;
}
}while(ch!=0);
}```
```OUTPUT:-
Enter any two number: 12 13
selection operation
2> Substriction
3> Multiply
4> Division
0> Exit