To Find Factorial of a Number

To Find Factorial of a Number

 

Factorial of a Number

 

For any positive number n, its factorial is given by:

factorial = 1*2*3*4....n

If a number is negative, factorial does not exist and factorial of 0 is 1.
This program takes an integer from a user. If user enters negative integer, this program will display error message and if user enters non-negative integer, this program will display the factorial of that number.

Source Code

/* C program to display factorial of an integer if user enters non-negative integer. */

 #include <stdio.h>
  int main()
{
    int n, count;
    unsigned long long int factorial=1;     /* you can only write int */    
    printf("\nEnter an integer: \n");
    scanf("%d",&n);
    if ( n< 0)
        printf("\nError!!! Factorial of negative number doesn't exist.\n");
    else
    {
       for(count=1;count<=n;++count)    /* for loop terminates if count>n */
       {
          factorial= factorial * count;       /* factorial=factorial*count */
       }
    printf("\nFactorial = %lu\n",factorial);  /* lu is for unsigned long long int */
    }
    return 0;
}

Output 1

Enter an integer: -5
Error!!! Factorial of negative number doesn't exist.

Output 2

Enter an integer: 10
Factorial = 3628800