Attempting to follow the pseudo-code here -- What exactly has been changed in PoW algorithms in the v7 fork?, I was curious about this part of the Monero hashing algorithm ...
scratchpad = fill_scratchpad(state)
What is the scratchpad for? When you "fill" the scratchpad, are you simply taking the value (state) from teh step above and prepending zeroes to it until you have 2 MB worth of data?