Machine-translated by Google. Questions are authored in English.
Top

Discussion

Which Boolean expression describes the output ‘X’ in the arrangement given below :

Logic diagram: inputs A, B and C-bar; C-bar goes through a NOT gate, the NOT output and B feed an OR gate, and the OR output and A feed an AND gate whose output is X.

  • A.X = a + (b · c)
  • B.X = a · (b + c)
  • C.X = (a · b) + c
  • D.X = a + b + c

Answer: B

The expression is X = a · (b + c). Reading the diagram from the left: the third input is C-bar, which passes through a NOT gate, so the signal that leaves the NOT gate is C. That signal and B go to the OR gate, which gives (b + c). The output of the OR gate and the input A go to the AND gate, so


\[ X = a \cdot (b + c) \]

The option a + (b · c) would need an AND on the first stage and an OR on the last, which is the reverse of the arrangement, and (a · b) + c would put a and b together. The expression a + b + c would be a single OR gate of the three inputs. The answer is X = a · (b + c).

No comment is present. Be the first to comment.
Loading…

Post your comment

Please log in or register to post a comment.