C PROGRAM FOR FACTORIAL

What is factorial of a number?

- actorial is denoted by the symbol '!'.example for , factorial of a number 4 is denoted as 4!. Factorial of a number is defined as the product of “the number and all integers less than that number except zero and negative integers”.

- Natural numbers ( non-negative integers ) which are greater than zero are used for factorial concept.

Factorial Example:

Zero factorial (0!) = 1
one factorial (1!) = 1
Two factorial (2!) = 2*1 = 2
Three factorial (3!) = 3*2*1 = 6
Four factorial (4!) = 4*3*2*1 = 24
Five factorial (5!) = 5*4*3*2*1 = 120
etc…

The common mathematical formula for finding factorial of the number ‘n’ is given below.

n! = n ( n – 1)( n – 2)( n – 3) …… (1)

Program

#include <stdio.h>
int main()
{
   int i,fact=1,num;  
   printf("\nPlease enter a number to find factorial : "); 
   scanf("%d",&num);
   if (num<0)
   {
      printf("\nPlease enter a positive number to");
      printf("find factorial and try again. \n");     
      printf("\nFactorial can't be found for negative");
      printf("values. It can be only positive or 0 \n");
      return 1;
   }
for(i=1;i<=num;i++)
   fact=fact*i;
printf("\n");
printf("Entered number is %d and it's factorial (%d!) is %d\n",num,num,fact);
    return 0;
}

Output

Please enter a number to find factorial : 7
Entered number is 7 and it’s factorial (7!) is 5040