MadeEasy Subject Test 2019: Digital Logic - Circuit Output

Question

Assume the operands are in 2’s Complement. To decrement A by 1, lines K,Cn and B should be :

• A. K = 1 , Cin = 1 , B = 1
• B. K = 0 , Cin = 1 , B = 1
• C. K = 0 , Cin = 1 , B = 0 
• D. K = 1 , Cin = 0 , B = 0

Answer 1

Answer is option C ?

Comments

Explain brother

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what is answer btw

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Its Option D

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This is the result i didn't understood last one 

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do by logic , let A2A1 = 11 means -1 in 2s complement , so we should get the result -2 i.e S2S1 = 10 by applying the inputs now put all th inputs u will get D as the result

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Brother please Elaborate your Example a little :)

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we can take any number like 11,10,01 it is in 2's complement number  in the form of  A2A1 now apply hit and trial for all option only option(d) is satisfy.