im trying to understand what is going on with the help of the schematic , in lesson 1.

Please give me some time.

I just need to clarify something.

when you write to all LATA register "0", is that just a number or is a bit? For example if we write

Code:
LATA = 5
Is that a number or is translated to a binary 00000101.

So this writting to lat register

Code:
LATA = 5 

represents the 

LATA = %00000101