Could someone post a snippet of assembly language code showing how subtraction with borrow works? I am trying to do 12 bit math on a

4 bit processor, but any example such as doing 16 bit math on an 8 bit processor will do. I don't care which processor either; I am just trying to find an example of someone using the carry bit as a borrow bit so I can work things out in my mind. The addition with carry makes perfect sense, but I don't "get it" when it comes down to doing subtraction with borrowing. An example would help a lot.Thanks!