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

Pop bits off your input and push them onto your output. Multiplying and dividing by 2 are the push and pop operations. In pseudo-code:

reverse_bits(x) {
    total = 0
    repeat n times {
       total = total * 2
       total += x % 2 // modulo operation
       x = x / 2
    }
    return total
}

See modulo operation on Wikipedia if you haven't seen this operator.

Further points:

• What would happen if you changed 2 to 4? Or to 10?
• How does this effect the value of n? What is n?
• How could you use bitwise operators (<<, >>, &) instead of divide and modulo? Would this make it faster?
• Could we use a different algorithm to make it faster? Could lookup tables help?