Question

When you first connect the computer to lan how does it understand the network topology?

Answer 1

So basically what we have our disc is all charge. Imagine a switch. It can either be ON (1) or OFF (0). that is what electric charge does to your disc, it can either leave some location on the disc charged (1) or can transfer some charge to another location that doesn't have charge ( converting 0 to 1 ).
So in the end what we have is a series of binary sequences. 

e.g. Something like this. ( at the lowest level / machine language )
 1010111111100001010101010101010010101010000001111010101010010101010101010101011111111010101110000101010101010101010111011111010101010101010101011111010101010101011111010101000000011111010101010101000011111

Terabytes of information in binary, just imagine.

Now we know that machine understands charge ( ON / OFF ) / ( 0 OR 1 ).

Now we have number systems such as binary, decimal, hexadecimal etc.
We are blessed to have great scientists who taught us to convert binary to other number systems such as decimal, Binary coded decimal etc.