How is the binary subtraction done in the photo attached? I know there are several ways to compute it, but I'm specifically asking for the way my professor did it in that photo.
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@an4s Glad to see that three of the serial down votes were removed. Sometimes this happens but it will be all right :) – Ѕᴀᴀᴅ Jun 24 '18 at 16:23
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@AlexFrancisco Yes, I realized it was one user who was not happy with my review to their answer. They downvoted 5 of my answers, of which 3 were reversed. – an4s Jun 24 '18 at 16:46
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You need to ask your professor for what the specific notation means, but it appears that s/he is just starting from the right hand side, and they are putting a line through the digit on the top line whenever they need to take a term from the next column.
So the zero in the third column becomes a "10" in binary as a 1 is taken from the fourth column. Since the number in the fourth column is a 0, a 1 can't be taken from it, so it becomes a "10" by taking a 1 from the fifth column (so that 1 becomes a 0). Now the the "10" in the fourth column becomes a 1 (since we need to take a one for the third column). That leaves a 1, which is written on the top row of the fourth column. I hope you get the idea as one continues in this way. This sounds like the Tom Lehrer song about new math.
number.seven
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Starting at the right:
- zero from one is one
- one from one is zero
- one from zero is not possible
- try to borrow from next column but cannot
- borrow from next to next column
- leaving one in next column and zero in next to next column
- one from two is one
- zero from one is one
- one from what is now zero is not possible
- borrow from next column
- leaving zero in next column
- one from two is one
- zero from what is now zero is zero
- zero from zero is zero
- zero from zero is zero
Henry
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