C Program to Find Factorial of a Number The factorial of a positive integer.

C Program to Find Factorial of a Positive Number

The factorial of a positive integer n is equal to 1*2*3*...n. You will learn to calculate the factorial of a number using for loop in this example.

The factorial of a positive number n is given by:

factorial of n (n!) = 1*2*3*4....n

The factorial of a negative number doesn't exist. And, the factorial of 0 is 1, 0! = 1

Example: Factorial of a Number

#include<stdio.h>
#include<conio.h>
int main()
{
        int a;
        int fact=1;
        printf("Enter an integer: \n");
        scanf("%d", &a);
        if(a<0)
       {
        printf("See Next Program to find factorial of 0 or negative value Thanks\n");
        }
        else
        {
          if(a>0)
        {  
         for(int i=1; i<=a; i++)  
        {  
           fact=fact*i;  
        }  
           printf("Factorial of the %d = %d", a, fact);
           return fact;
        }
        else
       {  
      if(a==0)  
      {  
           printf("See Next Program to find factorial of 0 or negative value Thanks\n");  
       }  
        }
}
getch();
}

Output

Enter an integer: 10
Factorial of 10 = 3628800

This program takes a positive integer from the user and computes factorial using for loop.

Since the factorial of a number may be very large, the type of factorial variable is declared as unsigned long long.

If the user enters negative number, the program displays error message.

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