self-doubt

Question

How do we perform 0 – 1 in 2’s complement subtraction  using 1-bit register??

Comments

$0-1=-1$

if u want to represent in $1$ bit, then sign bit not shown, only 1 will be in result

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For 0 - 1 

Using 2's complement in we could represent only -1 and 0 when no of bits=1.

The 2's complement of 1 is  1 and  when we add 0 with 2's complement of 1 then we  get1 as the answer and no carry and that is why we have a borrow of 1??

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Result should be in 1 bit

right?

• So, first do subtraction
• then do 2's complement
• and then take 1 rightmost bit as result