seriously speaking just excellent explanation... operation s are so complicated but it is now very cleared to me... as u have explained it so well thank you so much....
Those are just a bunch of extra bits, that are not part of the original message, to increase the length of the message to a number suitable for the algorithm
I show only one step of these 16 steps because all are identical. And then we will perform these 16 steps for each remaining 3 functions. So total steps for a single block is 64.