Computer Knowledge

Digital Logic and Microprocessors

735 Questions

Digital logic and microprocessors form the core of computer science, covering logic gates, combinational and sequential circuits, and CPU architecture. These topics are crucial for computer knowledge sections in technical exams. Test your digital electronics basics here.

Logic gates and circuitsCombinational vs sequential circuitsMicroprocessor instructionsTruth tables and boolean functions

Digital Logic and Microprocessors Questions

Multiple choice

Which of the following ports in 8255 microprocessor are basically bidirectional I/O pins that act as latched outputs or buffered inputs depending upon the control word loaded into the control word register?

  1. D0-D7

  2. PB0-PB7

  3. PA0-PA7

  4. PC0-PC7

  5. RD
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

These ports in 8255 microprocessor are basically bidirectional I/O pins that act as latched outputs or buffered inputs depending upon the control word loaded into the control word register.

Multiple choice

AND gate has 7 inputs. How many input words are in its truth table?

  1. 64

  2. 32

  3. 16

  4. 128

  5. 256
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

AND gate having 2 input has 4 input in truth table. AND gate having 3 input has 8 input in truth table. AND gate having 4 input has 16 input in truth table. AND gate having 5 input has 32 input in truth table. AND gate having 6 input has 64 input in truth table. AND gate having 7 input has 128 input in truth table.

Multiple choice

Consider two processes P1 and P2 accessing the shared variables X and Y protected by two binary semaphores Sx and Sy respectively, both initialized to 1. P and V denote the usual semaphore operators, where P decrements the semaphore value and V increments the semaphore value. The pseudo-codes of P1 and P2 are as follows:

In order to avoid deadlock, the correct operators at L1,L2,L3 and L4 are respectively

  1. P(SY),P(SX);P(SX),P(SY)

  2. P(SX),P(SY);P(SY),P(SX)

  3. P(SX),P(SX);P(SY),P(SY)

  4. P(SX),P(SY);P(SX),P(SY)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Here semaphores are required to obtain mutual exclusion since both access X & Y. So at L1 P (Sx) which means now S wait x = at L2 P (Sy) Sy wait, this prevents process P2 to start access X &Y. V(Sx) & V(Sy) in the end of P1 makes Sx & Sy signal so that at L3 & L4 P(Sx) & P(Sy) can start.