All you really need to know is this:
8 4 2 1 Hex Dec Oct ------------------------------- 0 0 0 0 0 0 0 0 0 0 1 1 1 1 0 0 1 0 2 2 2 0 0 1 1 3 3 3 0 1 0 0 4 4 4 0 1 0 1 5 5 5 0 1 1 0 6 6 6 0 1 1 1 7 7 7 1 0 0 0 8 8 10 1 0 0 1 9 9 11 1 0 1 0 A 10 12 1 0 1 1 B 11 13 1 1 0 0 C 12 14 1 1 0 1 D 13 15 1 1 1 0 E 14 16 1 1 1 1 F 15 17
Want to convert a hex number to binary? Just decode each hex digit (I know, it's not really a digit) to its 4-bit binary equivalent, left to right:
e.g. B5 hex => 10110101 binary
Want to convert that to an octal number? Just group the bits by threes, starting with the Least Significant Bits (LSB), then insert the octal equivalent for each group of three:
10 110 101 => 265 octal
That's the problem. These things are usually taught in big charts of numbers. It is a question of learning styles. I stare at these charts and my eyes glaze over! Can't do it. But when you put me in front of the panel and you showed me how there's a 4s place, 2s place, and 1s place, that made perfect sense. Just flip the switches that add up to the instruction for each set. I can do that.