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 operating modes in 8259A performs a non-specific End Of Interrupt (EOI) operation at the trailing edge of the last INTA pulse automatically?

  1. Fully nested

  2. Automatic EOI

  3. Special Mask

  4. Edge and Level Triggered

  5. Poll Command
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This operating mode in 8259A performs a non-specific End Of Interrupt (EOI) operation at the trailing edge of the last INTA (Interrupt Acknowledge) pulse automatically.

Multiple choice

Physical communication circuits are

  1. perfect

  2. not perfect

  3. both 1 and 2

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

Physical communication circuits are subject to various types of interference, noise, and signal attenuation, which can cause data errors. Because they are not perfect, network protocols must include mechanisms for error detection and correction to ensure reliable data transfer. This reality of physical media is why layers like the Data Link layer are essential.

Multiple choice

A logic gate is an electronic circuit which

  1. Make logic decisions

  2. Allows electron flow only in one direction

  3. Works on binary algebra

  4. Alternates between 0 and 1 values
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A logic gate is a fundamental building block of digital circuits that performs a logical operation on one or more binary inputs. It 'makes decisions' by producing a specific output (0 or 1) based on the logic of the gate (AND, OR, NOT, etc.).

Multiple choice

________________ is the state in instruction cycle that analyses the instruction to determine the type of operation to be performed and operands to be used.

  1. Instruction Address Calculation

  2. Instruction Fetch

  3. Operand Address Calculation

  4. Instruction Operation Decoding

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

This is the state in instruction cycle that analyses the instruction to determine the type of operation to be performed and operands to be used.

Multiple choice

What is the work of Output Feedback (OFB) mode?

  1. It does not produce the same ciphertext as that of plaintext.

  2. In this mode, the secret key is used to encrypt the plaintext block to form a ciphertext block.

  3. It is a block cipher implementation as a self-synchronising stream cipher.

  4. This block cipher implementation is conceptually similar to a synchronous stream cipher.

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

These are both correct about OFB.

Multiple choice

Directions: What is the full form of the abbreviation given in bold?

ECL

  1. Emission Coupled Logic

  2. Emitter-Coupled Logic

  3. Emotive Coupled Logic

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

Emitter-Coupled Logic (ECL) is a high-speed integrated circuit bipolar transistor logic family. It uses an overdriven differential amplifier with single-ended input and limited output voltage swing to avoid saturation.

Multiple choice

Directions: What is the full form of the abbreviation given in bold?

TTL

  1. Transparent Transistor Logic

  2. Translucent Transistor Logic

  3. Transistor Transfer Logic

  4. Transistor Transistor Logic
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Transistor-Transistor Logic (TTL) is a logic family built from bipolar junction transistors and resistors. It is called TTL because both the logic gating function and the amplifying function are performed by transistors.

Multiple choice

The only function of a NOT gate is a

  1. Stop a signal

  2. Recomplement a signal

  3. Invert an output signal

  4. Out as a universal gate
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A NOT gate, also known as an inverter, takes a single input signal and produces the opposite (inverted) output signal.

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).