# Program in C to reverse a given Number

Below is the C program to reverse a given number. This C program will accept a number (in a variable named “num”) and performs an operation to reverse the number.

```#include <stdio.h>
#include <stdlib.h>

int main(void) {

int num=1234, newNum=0;

while(num!=0){
newNum=newNum*10 + num%10;
num=num/10;
}

printf("\n");
printf("%d", newNum);

return 1;
}
```

Output: 4321

Explanation:

The statement while(num!=0) will be executed till value of num !=0

num%10 (read as num mod 10) will return the last digit. So in 1st iteration, it will return 4.

So, newNum will become–> 0*10 + 4 –>4

Next line i.e. num/10 will return 123

In the 2nd Iteration, newNum=4*10 + (num%10) –> 4*10 + 3 –> 43 and num = 123/10 = 12.

This loop continues until value of num becomes zero.

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### 9 Responses

1. Anonymous says:

It would be helpfull if every line’s function is explained.

2. LearnCOnline says:

The statement while(num!=0) will be executed till value of num !=0
num%10 (read as num mod 10) will return the last digit.
So in 1st iteration, it will return 4.
So newNum will become–> 0*10 + 4 –>4
next line i.e. num/10 will return 123

2nd Iteration:
newNum=4*10 + (num%10)–>4*10 + 3 –>43
num = 123/10 = 12

This loop continues until value of num becomes zero.
Hope its clear.

3. Dennis says:

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4. Anonymous says:

#include
#include
#include
#include

void main()
{
int num1, num2;
char str[10];
clrscr();

printf(“\nEnte the Number : “);
scanf(“%d”,&num1);

sprintf(str,”%d”,num1);

strrev(str);

num2 = atoi(str);

printf(“\nReversed Number : “);
printf(“%d\n”,num2);
getch();
}
(i think itz btr)

5. Anonymous says:

what about the reverse of a string????

6. Anonymous says:

Good explanation for reverse the number

7. LearnCOnline says:

Thank you everyone for the wonderful comments. I hope this website is helping every one out there.

If you like this website, kindly share it with everyone.

Thanks,
LearnCOnline Team

8. shanth says:

while(num!=0){
rev=num%10;
num=num/10;
}
print rev and watch