# Factorial of a Number in C using do-while Loop

Before going to the program first let us understand what is a Factorial of a Number?

Factorial of a Number:

The factorial of a Number n, denoted by n!, is the product of all positive integers less than or equal to n.

The value of 0! is 1 according to the convention for an empty product.

For example,

5 ! = 5 * 4 * 3 * 2 * 1 = 120

## Program code for Factorial of a Number in C:

```#include<stdio.h>
#include<conio.h>
void main()
{
int n,i=1,f=1;
clrscr();

printf("\n Enter The Number:");
scanf("%d",&n);

//LOOP TO CALCULATE THE FACTORIAL OF A NUMBER
do
{
f=f*i;
i++;
}while(i<=n);

printf("\n The Factorial of %d is %d",n,f);
getch();
}
```

## Working:

• First the computer reads the number to find the factorial of the number from the user.
• Then using do-while loop the value of ‘i’ is multiplied with the value of ‘f’.
• The loop continues till the value of ‘i’ is less than or equal to ‘n’.
• Finally the factorial value of the given number is printed.

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

Let us assume that the number entered by the user is 5.

1. It assigns the value of n=5 , i=1 , f=1
2. Then the loop continues till the condition of the do-while loop is true.

2.1.   do

f=f*i    (f=1*1)    So  f=1

i++      (i=i+1)    So  i=2

i<=n    (2<=5) , do-while loop condition is true.

2.2.   do

f=f*i    (f=1*2)    So  f=2

i++      (i=i+1)    So  i=3

i<=n    (3<=5) , do-while loop condition is true.

2.3.   do

f=f*i    (f=2*3)    So  f=6

i++      (i=i+1)    So  i=4

i<=n    (4<=5) , do-while loop condition is true.

2.4.   do

f=f*i    (f=6*4)    So  f=24

i++       (i=i+1)    So  i=5

i<=n    (5<=5) , do-while loop condition is true.

2.5.   do

f=f*i    (f=24*5)    So  f=120

i++       (i=i+1)    So  i=6

i<=n    (6<=5) , do-while loop condition is false.

2.6.   It comes out of the do-while loop.

1. Finally it prints as given below

The Factorial of 5 is 120

1. Thus the program execution is completed.

## Output:  ### 5 Responses

1. Vamshi says:

Awesome

• devang says:

Thank you Vamshi.. 🙂

2. Manoj j says:

Thanks. Helped me a lot.

3. Chandini says:

Thank u so much

4. D.venkatesh says:

thank you very much