Different results for factorial calculation in C, Python and JavaScript

Question

I wrote some simple code in Python, JavaScript and C. I found that the Python and JavaScript results are the same, but C gives me another -wrong- result and I can't understand what is the error.

C code:

int fact(int n){
    if(n==1){
        return 1;
    }else{
        return (n*fact(n-1));
    }
}

int main(void){
    printf("%i \n",fact(13));
}

JS code:

function fact(n){
    if (n==1){
        return (1);
    }else{
        return (n*fact(n-1));
    }
}

console.log(fact(13));

Python code:

def fact(n):
    if(n == 0):
        return 1
    else:
        return n * fact(n - 1)

print(fact(13))

Can you explain?

Answer 1

Being interpreted languages, they (probably) automatically choose the data type for variables according to the size of the data.

However, in C you specified that "int" has to be used - and it is way too small to hold 13!

If you switch "int" for "unsigned long long int" (yes, use "long" twice), then your program will return proper results for a longer time, until it fails again - exceeding the size of 64-bits.