###### UGC NET CS 2014 Dec-Paper-2

October 7, 2023###### Graphs

October 7, 2023# UGC NET CS 2014 Dec-Paper-2

Question 6 |

The BCD adder to add two decimal digits needs minimum of

6 full adders and 2 half adders | |

5 full adders and 3 half adders | |

4 full adders and 3 half adders | |

5 full adders and 2 half adders |

Question 6 Explanation:

→ Each digit is represented by a 4-bit BCD code.

→ To add two 4-bit number, we need 1 Half Adder(to add LSBs) and 3 Full Adders(remaining three bits of both number along with carry bits).

→ To make the resultant Sum as valid BCD sum, we need to add 0110 to the sum.

→ This can be done with 1 Half adder and 2 Full Adder

(Note: LSB bit of 0110 is always zero. So there is no need of ADDER to add LSBs.)

→ Here, Half adder is used to add next significant bits.

Total 5 Full Adders and 2 Half Adders are needed

→ To add two 4-bit number, we need 1 Half Adder(to add LSBs) and 3 Full Adders(remaining three bits of both number along with carry bits).

→ To make the resultant Sum as valid BCD sum, we need to add 0110 to the sum.

→ This can be done with 1 Half adder and 2 Full Adder

(Note: LSB bit of 0110 is always zero. So there is no need of ADDER to add LSBs.)

→ Here, Half adder is used to add next significant bits.

Total 5 Full Adders and 2 Half Adders are needed

Correct Answer: D

Question 6 Explanation:

→ Each digit is represented by a 4-bit BCD code.

→ To add two 4-bit number, we need 1 Half Adder(to add LSBs) and 3 Full Adders(remaining three bits of both number along with carry bits).

→ To make the resultant Sum as valid BCD sum, we need to add 0110 to the sum.

→ This can be done with 1 Half adder and 2 Full Adder

(Note: LSB bit of 0110 is always zero. So there is no need of ADDER to add LSBs.)

→ Here, Half adder is used to add next significant bits.

Total 5 Full Adders and 2 Half Adders are needed

→ To add two 4-bit number, we need 1 Half Adder(to add LSBs) and 3 Full Adders(remaining three bits of both number along with carry bits).

→ To make the resultant Sum as valid BCD sum, we need to add 0110 to the sum.

→ This can be done with 1 Half adder and 2 Full Adder

(Note: LSB bit of 0110 is always zero. So there is no need of ADDER to add LSBs.)

→ Here, Half adder is used to add next significant bits.

Total 5 Full Adders and 2 Half Adders are needed

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