遞迴實現十進位轉二進位

/* binary.c -- prints integer in binary form */#include <stdio.h>void to_binary(unsigned long n);int main(void){    unsigned long number;    printf("Enter an integer (q to quit):\n");    while (scanf("%ul", &number) == 1)    {        printf("Binary equivalent: ");        to_binary(number);        putchar('\n');        printf("Enter an integer (q to quit):\n");    }    printf("Done.\n");     return 0;}void to_binary(unsigned long n)   /* recursive function */{    int r; r = n % 2;    if (n >= 2)       to_binary(n / 2);    putchar('0' + r);      return;}