## Binary floating point Subtraction - binary-data

I was solving a binary subtraction and got stuck at a point. I am unable to understand how to subtract a larger number from a smaller number.
My operands are 0.111000*2^-3 and 1.0000*2^-3.
I have easily subtracted the fractional part but when coming to the MSB, I dont know how to do it. From where should I borrow to perform the operation. I know subtracting 1 from 0 requires a borrow and it turns sign bit to negative. But here, the storing is not under concern. My problem is with the operation itself. Could anyone explain wats the result and how to perform it??
Thanks

Very late, but had the same question so putting this here for others, having the same problem.
If your problem lies only at the fraction part, you could try this method:
1.000
- 0.111
-------
Step 1: Add sign bit of both binary numbers so you can add.
0 1.000
1 0.111
------- +
1 1.111
Now invert and add one to convert from 2's complement to sign-magnitude:
1 1.111 -> 0.001

Here is a great example that may help you:
http://sandbox.mc.edu/~bennet/cs110/pm/sub.html
If doing this programmatically, you can cheat and see which is larger before you perform the subtraction (which is what I do).

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