Factorial value of any integer by C language using while loop

 A C program to find the factorial value using while loop:

At first we have to know , what is factorial??

• In mathematics , the factorial of positive integer  n! , that is      n!=n x (n-1) x (n-2) x (n-3) ..........  x 3 x 2 x 1 .

For example , 6! = 6 x 5 x 4 x 3 x 2 x 1. However , 0!=1 .

       Now , we will do this through the C using while loop  . In C programming , we can do this various way . But we only run the program only while() loop .

Here is the source code :

 #include<stdio.h>  
 int main()  
 {  
       int x,y=1;  
       printf("Enter any integer :");  
       scanf("%d",&x);  
       if(x<0)  
       printf("Factorial of negative number does not exist .");  
       else{  
       while(x>=1)  
       {  
       y=y*x;  
   x--;  
       }  
         printf("The factorial of the above number is :%d",y);  
   }  
       return 0;  
 }  

Let us understand the above program with an example,

 we consider an integer 6 .

Using while() loop, 

    when x=6(Input)

    loop will be started after giving input .

     y= 6*1(as y=1)

next loop ,

    y=  6*(6-1) that is , y=6*5

next loop,

    y=30*(5-1) that is , y=30*4

next loop,

     y=120*(4-1) that is , y=120*3

next loop ,

     y=360*(3-1) that is , y=360*2

next loop,

     y=720*(2-1) that is , y=720*1

At this time , the loop will stop , as per condition .