 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