[kyubichan]

Okay it's something like this:

example...

Octal = 12

To convert to decimal:

12 => [ 2 x 8 (to the power of 0) ] + [ 1 x 8 (to the power of 1)]
= [2*1] + [ 1*8]
= 10

So, 12 base 8 is equal to 10 base 10.

To binary:

4 2 1 | 4 2 1 <== bits
0 0 1 | 0 1 0 <== binary
1 2 <== octal

So 12 base 8 is equal to 001010 base 2 (or just 1010).

I'm sorry about not elaborating earlier, I was off to school >.<