Namaran

print_digits.c

#include <stdio.h>

static void forward(unsigned n)
{
    if (n >= 10)
        forward(n / 10);
    putchar('0' + n % 10);
}

static void backward(unsigned n)
{
    putchar('0' + n % 10);
    if (n >= 10)
        backward(n / 10);
}

int main(void)
{
    forward(1203);
    putchar(' ');
    backward(1203);
    putchar('\n');
}