fib.c

#include <stdio.h>

int main(int argc, char *argv[])
{
    printf("Language: C\n");
    printf("%d\n", fib(atoi(argv[1])));
    return 0;
}

int fib(int n)
{
    if (n == 0)
        return 0;
    if (n == 1)
        return 1;
    return fib(n-1) + fib(n-2);
}

fib.nim

import os
import strutils


proc fib(n: int): int =
    if n == 0:
        return 0
    if n == 1:
        return 1
    return fib(n - 1) + fib(n - 2)

echo("Language: nim")
echo(fib(commandLineParams()[0].parseInt()))

fib.py

import sys

def fib(n):
    if n == 0: return 0
    if n == 1: return 1
    return fib(n - 1) + fib(n - 2)

print('Language: Python (' + sys.executable + ')')
print(fib(int(sys.argv[1])))

fib.rs

fn fib(n: i32) -> i32 {
    match n {
        0 => 0,
        1 => 1,
        _ => fib(n - 1) + fib(n - 2)
    }
}

fn main() {
    println!("Language: Rust");
    println!("{}", fib(40));
}