How to properly pad binary numbers (with and without radix)

So I've just got a quick question on padding with 0's. The examples I made are below, just assumed that length doesn't matter and there is no sign bit.

a) 1000 = 00000001000
b) 110.101 = 110.00000101
c) 110.101 = 110.10100000

I know that padding the integer part of a binary number in front is fine (notwithstanding buffers and stuff like that). Its more when I deal with radix points that I can never remember how it works. Do you pad beside the radix (b) or at the end of the digit (c). Also, does padding like this effect the complements of these numbers?

Thanks

EDIT: The reason I'm asking this is because I'm converting from binary to hex and binary to octal. To do this I have to grou开发者_运维问答p bits in groups of 4 or 3. I don't have enough bits so I need to add zeros somewhere.

Two's radix works the same way as the base-10 numbers (according to Wikipedia)

Thus, parts (a) and (c) are correct, but part (b) is not.

The bits to the left of the binary point should follow the same algorithm to find their complement, with the MSB of fractional bit being positive.