# C program for Palindrome Number using do-while Loop

Before going to the program first let us understand what is a *Palindrome Number?*

#### Palindrome Number:

It is a number which remains same even when the number is reversed.

For example,

Numbers like 0,1,2,11,44,121,222,242,345543 are called as Palindrome Numbers.

## Program code to find whether a Number is Palindrome or Not:

#include<stdio.h> #include<conio.h> void main() { int n,a,r,s=0; clrscr(); printf("\n Enter The Number:"); scanf("%d",&n); a=n; //LOOP TO FIND REVERSE OF A NUMBER do { r=n%10; s=s*10+r; n=n/10; }while(n>0); /* CHECKING IF THE NUMBER ENTERED AND THE REVERSE NUMBER IS EQUAL OR NOT */ if(a==s) { printf("\n %d is a Palindrome Number",a); } else { printf("\n %d is a not Palindrome Number",a); } getch(); }

**Related: **C++ program for Palindrome Number using do-while Loop

## Working:

- First the computer reads the number to find the reverse of the number.
- Then using do-while loop the reverse number is calculated.
- Then finally the reverse number is compared with the entered number and if they are equal then it is printed as “(Given number) is a palindrome number ” else it is printed as “(Given number) is not a palindrome number “.

## Step by Step working of the above Program Code:

Let us assume that the number entered by the user is 121.

- It assigns the value of s=0,n=121.
- Then it assigns the value of a=n (a=121).
- Then the loop continues till the condition of the do-while loop is true.

3.1. do

r=n%10 (r=121%10) So r=1

s=s*10+r (s=0*10+1) So s=1

n=n/10 (n=121/10) So n=12

n>0 (12>0) do-while loop condition is true

3.2. do

r=n%10 (r=12%10) So r=2

s=s*10+r (s=1*10+2) So s=12

n=n/10 (n=12/10) So n=1

n>0 (1>0) do-while loop condition is true

3.3. do

r=n%10 (r=1%10) So r=1

s=s*10+r (s=12*10+1) So s=121

n=n/10 (n=1/10) So n=0

n>0 (0>0) do-while loop condition is false

3.4. It comes out of the while loop and checks whether the number is palindrome or not.

- a==s (121==121) if condition is true

It prints 121 is a palindrome number.

- Thus the program execution is completed.

In the above working, step:4 if condition can also be false for some other number like ’12’.

Then for that it goes to the else part and prints 12 is not a palindrome number.

## Output:

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