How to Compare 2 Numbers Using 4bit Adder

Discussion in 'Homework Help' started by athulascc, Mar 27, 2015.

Aug 15, 2014
88
1
hi\
I need to compare Number A and B.
I can recognize equal state .

Also I know if A>B carry out will be 0.

but how to recognize A<B?

Aug 15, 2014
88
1

I think if A>B then answer is positive therefore Cout=0 , since for A=B Cout=0 when Cout=0 ; A>B or A=B

otherwise A<B

correct?

3. MikeML AAC Fanatic!

Oct 2, 2009
5,450
1,066
Can you subtract the two numbers, and look at the carry?

Aug 15, 2014
88
1
yes. they have given hint
B3 B2 B1 B0 - A3 A2 A1 A0 + 2^4
< 2^4

Aug 15, 2014
88
1
I know substractor does not show answer well when it is out of range or negative.

so I think only looking at carry out is not enough

6. WBahn Moderator

Mar 31, 2012
18,079
4,917
In your first post you said that you know how to recognize A=B and you know how to recognize A>B (though I'm not convinced you do, but let's assume). Well, then if you determine that A=B is not true AND you determine that A>B is not true, what does that leave as the only possible result?

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