factorial of a number in C

C program to find the factorial of a number is given below. Factorial of a number n is the product of all number in decreasing order starting from the number n to 1. Factorial doesn't exist for a negative number.

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

```include <stdio.h>
int main()
{
int n, i;
unsigned long long factorial = 1;
printf("Enter an integer: ");
scanf("%d",&n);
if (n < 0)
printf("Factorial of a negative number doesn't exist. Please enter a valid number");
else
{for(i=1; i<=n; ++i)
{factorial *= i;              // factorial = factorial*i;
}
printf("Factorial of %d = %llu", n, factorial);
}
return 0;}```

```output:Enter an integer: 5
Factorial of 5=120```

Factorial of a number using recursion

``````#include <stdio.h>
long int multiplyNumbers(int n);

int main()
{
int n;
printf("Enter a positive integer: ");
scanf("%d", &n);
printf("Factorial of %d = %ld", n, multiplyNumbers(n));
return 0;
}
long int multiplyNumbers(int n)
{
if (n >= 1)
return n*multiplyNumbers(n-1);
else
return 1;
}``````

```output:Enter an integer: 4
Factorial of 4=24```
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• Input (stdin)

Output (stdout)

Input (stdin)

Expected Output

Compiler Message

Input (stdin)

`2    3`

`5`
`5`
`5`