Do While Loop in C Programming
Program Abstraction: This programming tutorial explains the working of Do While loop in the concept of C programming.
Like the name indicate ‘do while’ loop do something first while the condition is hold.
General format of do-while loop:
|
do
{
Body of the loop;
}
while (condition);
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If you can’t understand anything, then this example will help you…
- Program to print first 5 number using do while loop:
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#include<stdio.h>
#include <conio.h>
int main()
{
int n=1;
do
{
printf(“%dn”,n);
n++;
}
while (n<=5);
getch();
}
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How this work?
At first, in ‘do’ block, printf and n++ works without checking any condition. After executing this block of codes, then ‘while’ condition is considered.
Difference between while loop and do while loop:
In while loop, body of the loop will execute if and only if the ‘while’ condition is satisfied, where as in do-while loop, body of the condition will execute at least once even the condition does not satisfied.
Example:
What will be the output of this program:
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#include<stdio.h>
#include <conio.h>
int main()
{
int n=5;
while (n<0)
{
printf(“%dn”,n);
n++;
}
getch();
}
|
So program does not display anything.
Same program in do while loop:
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#include<stdio.h>
#include <conio.h>
int main()
{
int n=5;
do
{
printf(“%dn”,n);
n++;
}
while (n<0);
getch();
}
|
Here what will the output?
do
{
printf(“%dn”,n);
}
Here ‘do’ block first print the value of n, ie 5,
Then execute: while (n<0);
Now check the condition. Here the while condition does not satisfied. But the ‘do-loop’ block should be executed its body at least once. So we got the output as 5 even the condition is false. But never print next numbers (due to n++), because the condition does not hold any more.
Another example for do while loop:
- Print odd numbers between 20 and 35:
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#include<stdio.h>
#include <conio.h>
int main()
{
int n=20;
do
{
if(n%2==1)
printf(“%dn”,n);
n++;
}
while (n<=35);
getch();
}
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if(n%2==1)
we leant already about modules operator (%) in a previous lesson. Here program check every number in between 20 and 35, if a number % 2 become 1, then number should be an odd and prints that number.
while(n<=35);
Check the number limitation exceeding 35.
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