Reverse bit pattern in C

Question

I am converting a number to binary and have to use putchar to output each number.

The problem is that I am getting the order in reverse.

Is the

Answer 1

I know: that is not exactly C, but I think that is an interesting answer:

int reverse(int i) {
  int output;
  __asm__(
     "nextbit:"
        "rcll $1, %%eax;"
        "rcrl $1, %%ebx;"
        "loop nextbit;"
        : "=b" (output)
        : "a" (i), "c" (sizeof(i)*8) );
  return output;
}

The rcl opcode puts the shifted out bit in the carry flag, then rcr recovers that bit to another register in the reverse order.