fib.c

#include <stdio.h>
#include <stdlib.h>

static unsigned int fib(unsigned int param)
{
    if (param < 0) {
        return 0;
    }
    if (param == 1 || param == 2) {
        return 1;
    }
    return fib(param - 1) + fib(param - 2);
}

int main(int argc, char *argv[])
{
    //  No Error Processing
    printf("%d", fib(atoi(argv[1])));
}