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();
}

Related: Factorial of a Number in C++ using do-while Loop

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.

3. Finally it prints as given below

The Factorial of 5 is 120

4. Thus the program execution is completed.

Output:

TO DOWNLOAD THE PROGRAM CODE :CLICK HERE