To base

#include <stdio.h>
void to_base(unsigned long n, int base);

int main(void){
    unsigned long number;
    int base=2;
    printf("Enter an integer (q to quit):\n");
    while(scanf("%lu", &number)==1 && (base>=2 && base<=10)){
        printf("Enter a base to convert to (2-10):");
        scanf("%d", &base);
        printf("Binary equivalent: ");
        to_base(number, base);
        putchar('\n');
        printf("Enter an integer (q to quit):\n");
    }

    printf("Done.\n");

    return 0;
}

void to_base(unsigned long n, int base){
    int r;

    r=n%base;
    if (n>=base)
        to_base(n/base, base);
    putchar('0'+r);

    return;
}