ISRO2015-7

Question

If half adders and full adders are implements using gates, then for the addition of two $17$ bit numbers (using minimum gates) the number of half adders and full adders required will be

• A. $0,17$
• B. $16,1$
• C. $1,16$
• D. $8,8$

Comments

explain it in detail

 

 

plz

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We have two 17 bit numbers, one adder is used for adding one bit so for the least significant bit we don't need any full adder as we always  have 0 as initial carry for the LSB so we can add LSB using half adder but for rest of the 16 bits from 2nd bit from right to MSB we need full adder because carry can be generated by them hence there is need of 16 full adder.

Hence option C) is correct

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same question - https://gateoverflow.in/1494/gate1999-2-16

Answer 1

for implementation n-bit of parallel adder n bit full adder required.

n bit full adder = (n-1) full adder and 1 half adder required.

so accoring to the question 16 full adder and 1 half adder required.

so option c is correct.