Print decimal binary in C

print.c

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

void print_dec_bin(uint64_t d);

int main(int argc, char const *argv[]) {
  print_dec_bin(0);
  print_dec_bin(1);
  print_dec_bin(7);
  return 0;
}

void print_dec_bin(uint64_t n) {
  int c, k;
  printf("%ld: ", n);
  for (c = 63; c >= 0; c--) {
    k = n >> c;
    if (k & 1) {
      putc('1', stdout);
    } else {
      putc('0', stdout);
    }
    if (!(c % 8)) {
      putc(' ', stdout);
    }
  }
  putc('\n', stdout);
}