What is the minimum number of two-input NAND gates used to perform the function of two input OR gate ?
A.
one
B.
two
C.
three
D.
four
Answer: Option C
Explanation:
Y=A+B. This is the equation of OR gate. We require 3 NAND gates to create OR gate. We can also write
After 1st NAND operation Y = (A AND B)' Y= A' + B' (Demorgan's Law) After 2nd NAND operation Y= ( A' + B')' Y= A . B (Demorgan's Law) After 3rd NAND operation Y= ( A . B )' Y= A' + B ' (Demorgan's Law)
The number of full and half-adders required to add 16-bit numbers is:
A.
8 half-adders, 8 full-adders
B.
1 half-adder, 15 full-adders
C.
16 half-adders, 0 full-adders
D.
4 half-adders, 12 full-adders
Answer: Option B
Explanation:
The one half-adder can add the least significant bit of the two numbers. Full adders are required to add the remaining 15 bits as they all involve adding carries.