I wanted to know how I would subtract two hexadecimal values from each other when more than one borrow is needed.
Given 0x00000200 - 0x00000004
Here is what I tried (starting from the right most digit), I borrow a 1 from the third column and the second column becomes F. I then borrow a 1 from the second column and that becomes E and the first column becomes a F. Now I do the actual subtraction and I get 1EC.
The actual answer is 1FC, am I missing something here? Don't you need to borrow from the second column?
If that were correct, you’d get $186$ when subtracting $4$ from $200$ in ordinary decimal notation, instead of the correct $196$.
Henceforth everything is in hexadecimal. When you borrow $1$ from the third column, the top of the second column becomes $10$, not $\text{F}$; then you borrow $1$ from that, and it drops to $\text{F}$, while you get $10$ at the top of the first column. Then $10-4=\text{C}$, $\text{F}-0=\text{F}$, and $1-0=1$, giving you the correct answer of $1\text{FC}$.