What number is represented by the byte 00000001?

The short answer: one is always one in any number base.

Here's a method to decode binary numbers. Make a column for each digit, and starting from the right, put a "1" and then as you move left put double the value of the column next to it. Remember, right-to-left ( THIS WAY ). You'll get something like this, which is a horizontal version of the helper table shown in the quz:

128  64  32  16   8   4   2   1   <-- 8 columns for 8 digits

Then, put your binary number on the next line, spread into the columns. Now below that, multiply each top number by the binary digit and put the result below. It's easy, since binary digits are either 1 or 0, so you either put the number on top again or zero.

Then finally, add up all the numbers on the bottom row and that's your answer. Using 00000111 for an example:

128  64  32  16   8   4   2   1   <-- starting columns
  0   0   0   0   0   1   1   1   <-- multiply by your binary digits
--- --- --- --- --- --- --- ---
  0   0   0   0   0   4   2   1   <-- add these up:  4 + 2 + 1  =  7

Also, since zeros in front don't count you can skip them. So in this case we really only needed 3 columns.

In this specific case, 00000001 has only the rightmost digit set to 1, so the result is 1. As I mentioned in the title, this would be true no matter what number system was being used.