GATE CSE 1992 | Question: 02-ii

Question

All digital circuits can be realized using only

• A. Ex-OR gates
• B. Multiplexers
• C. Half adders
• D. OR gates

Comments

Half-Adder, and MUX both need help of constant 1, and can realize all logic circuits, hence B,C are the correct options.

Answer 1

Answer: B, C

NOR gate, NAND gate, Multiplexers and Half adders can also be used to realise all digital circuits.

Comments

I don't think they have used any Partially functional Complete term in Gate, So it is either complete or not complete.

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So do we consider Half adder as functionally complete or not in GATE?

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@sambhrant , @vishalshrm539 

find "It is not functionally complete then" on https://gateoverflow.in/157184/functionally-complete-sets

Answer 2

Half adders are not fully functionally complete they are partially functionally complete.

So, most appropiate answer should be MULTIPLEXERS i.e. (b)

 

Thanks :)

Comments

given the logic 0 and 1 as input , we can use half adders to compute any function

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Even MUX requires, 0 and 1 inputs to be functionally complete.

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@sushmita, Even multiplexer requires logic 0 & 1 to become functionally complete. Same is the case with half-adder. So why only multiplexer is answer?

@arjun sir, I feel answer by Rajarshi Sarkar should be the selected answer.

Answer 3

They didn't Ask you only functional complete

 They just asking "All digital circuits can be realized using only"

so, here comes both partially FC and FC

So, Answer should be B and C

Answer 4

Only Mux is functionally complete.

Desired option Is only B..

Comments

in case of half adder sum =AxorB and Carry=AB

in this question if Sum expression and carry expression independently fuctionally complete then it is included my answer but in this case it is not possible my answer is Multiplexer