Computer Knowledge

Digital Logic and Microprocessors

749 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

A circuit outputs a digit in the form of 4 bits. 0 is represented by 0000,1 by 4,..., 9 by 1001. A combinational circuit is to be designed that takes these 4 bits as input and outputs 1 if the digit ³ 5, and 0 otherwise. If only AND, OR and NOT gates may be used, what is the minimum number of gates required?

  1. 2

  2. 3

  3. 4

  4. 5
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The condition digit >= 5 for a 4-bit input (d3 d2 d1 d0) is true for inputs 5 (0101) through 9 (1001). The Boolean expression is f = d3 + d2*d1 + d2*d0, which can be implemented with 4 gates (two ANDs, two ORs).

Multiple choice

The recognizing capabilities of NDFSM and DFSM where NDFSM - non deterministic finite state machine and DFSM - deterministic finite state machine

  1. may be different

  2. must be different

  3. must be same

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Non-deterministic finite state machines (NDFSM) and deterministic finite state machines (DFSM) are equivalent in terms of the class of languages they can recognize, which is the class of regular languages.

Multiple choice

What is the major difference between Moore and Mealy machines?

  1. The output of the former depends on the present state and present output.

  2. The output of the former depends only on the present state.

  3. The output of the former depends only on the present input.

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In a Moore machine, the output is determined solely by the current state. In a Mealy machine, the output depends on both the current state and the current input.

Multiple choice

Which of the following is/are Universal Logic Gates?

  1. NAND

  2. NOT

  3. NOR

  4. Both (1) and (3)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

NAND and NOR are Universal Logic Gates because these gates have the properties of combinations in them which can be used to accomplish any of the basic operations and can thus produce an inverter, OR / AND gate.

Multiple choice

Which of the following is the indicator of flags in status register in ALU?

  1. Carry

  2. Zero

  3. Sign

  4. All of the above

  5. Parity

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Flags hold a single bit to indicate certain conditions that arise during arithmetic and logical operations. The imporatant flag indicators are Carry , Zero , Sign and Parity .  Flags hold a single bit to indicate certain conditions that arise during arithmetic and logical operations. The imporatant flag indicators are Carry , Zero , Sign and Parity . 

Multiple choice

How can we implement DRAM cells?

  1. By using capacitors

  2. By using flags

  3. By using flip flops

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

DRAM cells are implemented by using capacitors, because they periodically refreshed, in a very short time.