program to find GCD using recursion

//also help to understand the command line argument

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

int gcd(int, int);

int main(int argc, const char* argv[])       //command line argument
{
    int a, b;
    a = atoi(argv[1]);
    b = atoi(argv[2]);
   
    printf("The greatest commaon divisor of %d and %d is %d\n", a, b, gcd(a,b));
    return 0;
}

int gcd(int a, int b)
{
    if (b == 0)
        return a;                   //recursion implementation
    else
        return gcd(b, a % b);
}