Q1.

Write a short note on Encoder

An encoder is a combinational logic circuit that compresses multiple binary inputs into a smaller
number of outputs. For example, an 8-to-3 encoder takes 8 inputs and encodes them into 3 output
lines. Encoders reduce the complexity of data handling in digital systems.
Types:
1. Priority Encoder: Assigns priority to inputs when multiple inputs are active.
2. Decimal to Binary Encoder: Encodes decimal inputs to binary outputs.
Applications:
• Used in digital systems like calculators, keyboards, and data selectors.
Example Truth Table for 4-to-2 Encoder:
Input (D0-D3) Output (Y1 Y0)
0001 00
0010 01
0100 10
1000 11

Q2. Write a short note on Decoder

A decoder is a combinational circuit that converts binary input data into a unique output line. It
performs the opposite function of an encoder. For example, a 3-to-8 decoder uses 3 inputs to
produce 8 outputs.
Types:
1. Binary to Decimal Decoder: Converts binary numbers to decimal equivalents.
2. Address Decoder: Decodes memory addresses.
Applications:
• Memory addressing, instruction decoding, and digital systems.
Example Truth Table for 2-to-4 Decoder:
Input (A1 A0) Output (O0 O1 O2 O3)
00 1000
01 0100
10 0010
11 0001

Q3. Write a short note on Multiplexer

A multiplexer (MUX) is a combinational circuit that selects one input from multiple inputs and
forwards it to the output based on selection lines.
Characteristics:
• Uses 2ⁿ inputs, n selection lines, and 1 output.
• Enables efficient data selection.
Applications:
• Data routing, communication systems, and ALUs in processors.
Example Truth Table for 2-to-1 MUX:
Select Line (S) Input (I0 I1) Output (Y)

0 X0 0

1 X1 1
Q4. Write a short note on De-Multiplexer
A de-multiplexer (DEMUX) is a circuit that takes a single input and channels it to one of several
outputs, determined by select lines.
Characteristics:
• One input, multiple outputs.
• Acts as a reverse of a multiplexer.
Applications:
• Communication systems, memory chip selection, and microprocessors.
Example Truth Table for 1-to-4 DEMUX:
Select Lines (S1 S0) Input (I) Output (Y0 Y1 Y2 Y3)
00 1 1000
01 1 0100
10 1 0010
11 1 0001
Here are detailed and more informative answers to the questions:
Q5. Truth Table, Symbols, and Expressions of All Logic Gates
Logic gates are the fundamental building blocks of digital circuits. They perform basic logical
operations on one or more binary inputs and produce a single binary output.
Types of Logic Gates:
1. AND Gate
o Symbol: A flat-topped shape with two or more inputs converging.
o Expression: Y=A⋅BY = A \cdot B
o Truth Table:
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
2. OR Gate
o Symbol: A curved-topped shape with two or more inputs.
o Expression: Y=A+BY = A + B
o Truth Table:
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
3. NOT Gate
o Symbol: A triangle with a small circle at the tip.
o Expression: Y=A‾Y = \overline{A}
o Truth Table:
A Y
0 1
1 0
4. NAND Gate
o Symbol: An AND gate with a circle at the output.
o Expression: Y=A⋅B‾Y = \overline{A \cdot B}
o Truth Table:
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
5. NOR Gate
o Symbol: An OR gate with a circle at the output.
o Expression: Y=A+B‾Y = \overline{A + B}
o Truth Table:
 A B Y
0 0 1
0 1 0
1 0 0
1 1 0
6. XOR Gate
o Symbol: An OR gate with an additional curve before the inputs.
o Expression: Y=A⊕B=(A⋅B‾)+(A‾⋅B)Y = A \oplus B = (A \cdot \overline{B}) +
(\overline{A} \cdot B)
o Truth Table:
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
7. XNOR Gate
o Symbol: An XOR gate with a circle at the output.
o Expression: Y=A⊕B‾=(A⋅B)+(A‾⋅B‾)Y = \overline{A \oplus B} = (A \cdot B) +
(\overline{A} \cdot \overline{B})
o Truth Table:
A B Y
0 0 1
0 1 0
1 0 0
1 1 1
Q6. Explain Flip-Flops (SR, JK, T, D)
A flip-flop is a bistable multivibrator used to store 1-bit of binary data. Flip-flops are the building
blocks of sequential circuits and are controlled by clock pulses.
Types of Flip-Flops:
1. SR (Set-Reset) Flip-Flop
o Operation: Two inputs: Set (S) and Reset (R).
▪ Set S=1,R=0S = 1, R = 0: Q = 1 (Set state).
▪ Reset S=0,R=1S = 0, R = 1: Q = 0 (Reset state).
o Truth Table:
S R Q
0 0 Hold
0 1 0
1 0 1
1 1 Invalid
2. JK Flip-Flop
o Improved SR Flip-Flop that avoids the invalid state.
o Operation:
▪ J=1,K=0J = 1, K = 0: Set state.
▪ J=0,K=1J = 0, K = 1: Reset state.
▪ J=1,K=1J = 1, K = 1: Toggle state.
3. T (Toggle) Flip-Flop
o Operation: Single input (T). Toggles state when T=1T = 1.
o Use: Counters and frequency dividers.
4. D (Data) Flip-Flop
o Operation: Single input (D). Output follows the input when a clock pulse is present.
o Use: Data storage and registers.
Applications:
• Used in registers, counters, and memory circuits.
Q7. Difference Between Hardwired and Microprogrammed Control Unit
Feature Hardwired Control Unit Microprogrammed Control Unit
Control logic is implemented using fixed Control logic is implemented using a set of
Definition
hardware circuitry. instructions (microprogram).
Faster because operations are Slower due to fetching and decoding
Speed
performed directly through circuits. microinstructions.
Not flexible; changes require hardware Flexible; changes can be made by updating
Flexibility
modification. microinstructions.
Complexity Complex design and debugging process. Simplified design using control memory.
Expensive due to the complexity of
Cost Cost-effective for complex systems.
hardware design.
Used in RISC processors where speed is Used in CISC processors where flexibility is
Usage
critical. important.
Applications:
• Hardwired: High-performance systems, e.g., GPUs.
• Microprogrammed: General-purpose processors, e.g., Intel and AMD CPUs.
Q8. Difference Between SRAM and DRAM
Feature SRAM (Static RAM) DRAM (Dynamic RAM)
Definition Stores data using flip-flops. Stores data using capacitors.
Slower because data needs to be
Speed Faster due to no refresh requirement.
refreshed.
Power Low when idle but high during
Consumes less power overall.
Consumption operation.
Density Lower density, more expensive. Higher density, less expensive.
Usage Used in CPU caches. Used as main memory (RAM).
Data Retention Retains data until power is lost. Loses data quickly without refreshing.

Q9. Difference Between Computer Organization and Architecture

Aspect Computer Organization Computer Architecture
Deals with the operational units and their Focuses on the design and functionality of
Definition
interconnections. the system.
Concerned with specification and
Scope Concerned with implementation.
functionality.
Example How control signals are generated. Instruction set, addressing modes, etc.
Dependency Independent of architecture. Determines the organization.
System design aspects like ISA (Instruction
Focus Hardware components like ALU, CPU, etc.
Set Architecture).

Q10. Micro-Instruction Sequencing

Micro-instruction sequencing defines the order in which microinstructions are executed to perform a
specific operation.
Key Points:
1. Control Memory: Stores microinstructions.
2. Sequencer: Determines the next microinstruction based on the current state.
3. Sequencing Techniques:
o Sequential Execution: Executes instructions in order.
o Conditional Execution: Branches based on conditions.
o Looping: Repeats a set of instructions.
Applications:
• Used in control units for executing complex instructions efficiently.
Q11. Cache Memory in Detail
Cache memory is a small, high-speed memory located close to the CPU. It stores frequently accessed
data to reduce the time required to fetch data from main memory.
Types of Cache:
1. L1 Cache: Smallest and fastest, located within the CPU.
2. L2 Cache: Larger but slower, may be shared among cores.
3. L3 Cache: Largest and slowest, shared across the CPU.
Working:
1. CPU checks cache for data.
2. If found (cache hit), data is retrieved quickly.
3. If not found (cache miss), data is fetched from main memory and stored in the cache.
Cache Mapping Techniques:
1. Direct Mapping: Each block has a fixed cache location.
2. Associative Mapping: Data can be stored in any cache line.
3. Set-Associative Mapping: Combines direct and associative mapping.
Applications:
• Improves performance in applications requiring frequent data access.

Q12. Characteristics of Memory

1. Access Time: Time taken to access a specific memory location.
2. Storage Capacity: Amount of data a memory unit can store.
3. Volatility: Determines whether memory retains data without power (e.g., RAM vs ROM).
4. Cost: Varies based on speed and technology (e.g., SRAM > DRAM).
5. Physical Size: Determines the compactness of the memory unit.
6. Durability: Determines resistance to data degradation over time.
Q13. Write a Note on Interleaved Memory
Interleaved memory is an advanced memory organization technique designed to enhance system performance
by enabling parallel access to memory blocks. Instead of accessing a single memory block at a time, the
memory is divided into smaller banks, and multiple banks can be accessed concurrently.
Key Concepts:
1. Structure:
o The memory is divided into nn banks, each capable of independent operation.
o Each bank has its own address decoder and can be accessed simultaneously.
2. Working Principle:
o Low-order Interleaving: The least significant bits of the memory address determine the bank
number.
o High-order Interleaving: The most significant bits determine the bank number.
o Allows overlapping access cycles to reduce idle time and improve throughput.
3. Applications:
o Used in high-performance computing systems like supercomputers.
o Often found in graphics processors and parallel processing architectures.
Advantages:
• Increased data throughput.
• Reduced memory latency and improved overall system performance.
Disadvantages:
• Requires sophisticated hardware for managing simultaneous accesses.
• May not be effective for sequential memory access patterns.
Q14. Flynn’s Classification
Flynn’s taxonomy categorizes computer architectures based on instruction and data streams. It
provides a framework to analyze parallelism in computing systems.
Categories:
1. SISD (Single Instruction, Single Data):
o A single instruction operates on a single data set at a time.
o Sequential execution, no parallelism.
o Example: Traditional uniprocessor systems.
2. SIMD (Single Instruction, Multiple Data):
o A single instruction operates on multiple data sets simultaneously.
o High data-level parallelism.
o Example: GPUs and vector processors.
3. MISD (Multiple Instruction, Single Data):
o Multiple instructions operate on a single data stream.
o Rarely used in practice, mainly theoretical.
o Example: Some fault-tolerant systems.
4. MIMD (Multiple Instruction, Multiple Data):
o Multiple instructions operate on multiple data streams.
o Supports task-level parallelism.
o Example: Multi-core processors and distributed systems.
Applications:
• SISD: Personal computers, laptops.
• SIMD: Image and signal processing.
• MIMD: Supercomputers, servers.

Q15. IEEE 754 Standard

The IEEE 754 standard is a widely used representation for floating-point numbers in computers. It
defines how real numbers are stored and manipulated.
Components:
1. Sign (1 bit): Determines whether the number is positive (0) or negative (1).
2. Exponent: Stores the range of the number.
3. Mantissa (Fraction): Represents the significant digits of the number.
Formats:
1. Single Precision (32-bit):
o 1-bit sign, 8-bit exponent, 23-bit mantissa.
o Suitable for applications where precision can be compromised.
2. Double Precision (64-bit):
o 1-bit sign, 11-bit exponent, 52-bit mantissa.
o Used in scientific and high-precision applications.
Formula:
Value=(−1)S×1.M×2E−B\text{Value} = (-1)^{S} \times 1.M \times 2^{E-B},
Where SS: Sign, MM: Mantissa, EE: Exponent, BB: Bias (e.g., 127 for single precision).
Advantages:
• Standardized representation ensures portability.
• Supports a wide range of values with high precision.
Q16. Bus Arbitration Mechanism
Bus arbitration manages access to a shared system bus in a multi-device environment, ensuring fair
and efficient communication.
Key Techniques:
1. Centralized Arbitration:
o A central arbiter controls the bus access.
o Examples:
▪ Daisy Chaining: Devices are connected in sequence, and access is passed
down the chain.
▪ Polling: The arbiter queries devices in a fixed order.
▪ Priority-Based: Devices are assigned priority levels.
2. Distributed Arbitration:
o No central arbiter; devices use protocols to decide bus access.
o Example: Ethernet.
Factors to Consider:
• Fairness among devices.
• Minimizing bus contention.
• Maximizing bus utilization.

Q17. Write a Short Note on Buses

A bus is a communication system that transfers data between components inside a computer or
between computers.
Types of Buses:
1. Data Bus: Transfers actual data between components.
2. Address Bus: Transfers memory or I/O addresses, unidirectional.
3. Control Bus: Carries control signals like read/write operations.
Bus Characteristics:
1. Width: Determines the amount of data transmitted in one cycle.
2. Speed: Influences data transfer rate.
3. Architecture:
o Single Bus: Simplifies design but may cause bottlenecks.
o Multiple Bus: Improves performance but increases complexity.
Applications:
• Facilitates data transfer in motherboards, peripherals, and networked devices.
Q18. Explain Von Neumann Model
The Von Neumann Model, introduced by John von Neumann, is a computer architecture where both
program instructions and data are stored in the same memory. It forms the foundation for most
modern computers.
Key Components:
1. CPU: Contains the ALU for calculations, Control Unit to manage operations, and Registers for
temporary storage.
2. Memory: Stores both data and instructions (RAM for primary memory, disk for secondary
storage).
3. I/O Devices: Allow interaction with the computer (e.g., keyboard, monitor).
4. Bus System: Transfers data, addresses, and control signals between components.
Working:
1. Fetch: Retrieve instruction from memory.
2. Decode: Understand the instruction.
3. Execute: Perform the operation using the ALU.
4. Store: Save results back to memory.
Advantages:
• Simplicity and cost-effectiveness due to shared memory.
• Flexibility in storing instructions and data.
Disadvantages:
• Von Neumann Bottleneck: Shared memory bus limits speed.
• Limited Parallelism: Sequential instruction fetching.
In comparison to the Harvard architecture, Von Neumann uses a single memory for both instructions
and data.
Q19. Data Hazards and Bench Hazards
Data Hazards:
Data hazards occur in pipelined processors when instructions that are executed concurrently depend on each other's data.
They delay instruction execution and degrade performance.
Types of Data Hazards:
1. Read After Write (RAW):
o Also called true dependency.
o Occurs when an instruction tries to read a result that has not yet been written by a preceding
instruction.
2. Write After Read (WAR):
o Also called anti-dependency.
o Occurs when an instruction writes to a location before a preceding instruction reads it.
3. Write After Write (WAW):
o Also called output dependency.
o Occurs when multiple instructions write to the same location in an incorrect order.
Solutions:
• Pipeline stalling.
• Data forwarding (bypassing).
• Reordering instructions.
Branch Hazards:
Branch hazards occur when the pipeline makes incorrect predictions about the flow of control (e.g., jumps or conditional
branches).
Effects:
• Causes delays as the pipeline needs to discard partially processed instructions.
Solutions:
• Branch prediction algorithms.
• Delayed branching.
Q20. Register Organization, Instruction Format, and Addressing Modes
Register Organization:
Registers are the smallest and fastest memory units within the CPU. They temporarily store data and
instructions for immediate access.
Types of Registers:
1. General Purpose Registers (GPRs): Hold intermediate data and operands.
2. Special Purpose Registers: Include:
o Program Counter (PC): Tracks the next instruction.
o Accumulator (AC): Stores arithmetic results.
o Instruction Register (IR): Holds the current instruction.
Instruction Format:
Instruction format specifies how an instruction is represented. It includes:
1. Opcode: Specifies the operation to be performed.
2. Operand: Specifies the data or memory location.
3. Addressing Mode: Indicates how to interpret the operand.
Examples:
• 1-Address Instruction: Contains one operand and an implicit accumulator.
• 2-Address Instruction: Two operands (source and destination).
• 3-Address Instruction: Three operands for complex operations.
Addressing Modes:
Addressing modes define how the operand's location is determined.
1. Immediate: Operand is specified directly in the instruction.
2. Direct: Address of the operand is specified.
3. Indirect: Address points to another address containing the operand.
4. Indexed: Base address plus an offset.
5. Register: Operand is in a register.

Q21. Addressing Modes

Addressing modes dictate how the operand of an instruction is specified and accessed.
Purpose:
1. Provides flexibility in instruction design.
2. Reduces program size by offering multiple ways to specify data.
Common Addressing Modes:
1. Immediate Mode: Operand is part of the instruction itself.
o Example: ADD A, 5 (5 is directly added to A).
2. Direct Mode: The instruction specifies the memory location of the operand.
o Example: MOV A, [1000] (Load the value from address 1000 into A).
3. Indirect Mode: The instruction specifies an address that contains the actual address of the operand.
o Example: MOV A, [B] (Load the value from the address stored in B).
4. Indexed Mode: Adds an index value to a base address to determine the operand’s location.
o Example: MOV A, [Base + Index].
5. Register Mode: Operand resides in a register.
o Example: ADD A, B (Add the contents of B to A).
6. Relative Mode: Used in branch instructions; offset is added to the program counter.
Advantages:
• Efficient use of memory.
• Supports complex data structures like arrays and pointers.
Q22. Cache Write Policies
Cache memory write policies govern how data is written to the cache and the main memory. These
policies impact performance and consistency.
Common Cache Write Policies:
1. Write-Through:
o Data is written to both the cache and main memory simultaneously.
o Advantages: Ensures data consistency.
o Disadvantages: Slower due to frequent main memory writes.
2. Write-Back:
o Data is written to the cache only, and main memory is updated later.
o Advantages: Reduces memory write operations.
o Disadvantages: Requires dirty bit tracking and can cause data inconsistency during
failures.
3. Write Allocate:
o On a write miss, data is loaded into the cache before writing.
o Improves locality.
4. No-Write Allocate:
o Data is directly written to the main memory, bypassing the cache.
Considerations:
• Write policies are chosen based on system requirements for speed and consistency.

Q23. Booth’s Algorithm

Booth’s Algorithm is a method for efficient multiplication of binary numbers, particularly for signed
numbers. It reduces the number of operations required.
Steps:
1. Initialization:
o Load the multiplicand (M), multiplier (Q), and an auxiliary register (A) set to 0.
2. Examine Multiplier:
o Check Q's least significant bit (Q0) and an additional bit (Q-1).
3. Operation:
o Q0 = 1, Q-1 = 0: Subtract M from A.
o Q0 = 0, Q-1 = 1: Add M to A.
o Q0 = Q-1: No operation.
4. Shift: Perform arithmetic right shift of (A and Q).
5. Repeat: Continue for the number of bits in the multiplier.
Advantages:
• Handles signed numbers easily.
• Efficient for numbers with consecutive 0s or 1s.
Q24. Beginning Product in Multiplication
The beginning product refers to the initial setup and first steps in binary multiplication, especially in
algorithms like Booth's. It involves preparing operands, initializing registers, and determining the
initial partial product that will be modified through successive steps.
Steps:
1. Operand Setup:
o Multiplicand (M): The number being multiplied.
o Multiplier (Q): The number by which the multiplicand is multiplied.
2. Initialization:
o Set Accumulator (A) to 0.
o Set Q-1 (extra bit) to 0.
o Both multiplicand and multiplier are loaded into memory or registers.
3. Partial Products:
o The least significant bit (LSB) of the multiplier decides whether to add, subtract, or
skip the multiplicand during each step.
4. Shifting:
o Arithmetic or logical shifts are performed to align the product and intermediate
results.
Example:
For multiplicand M=1011M = 1011 and multiplier Q=0110Q = 0110, the initial product setup would
involve placing them in appropriate registers, preparing to perform shifts and additions/subtractions
based on the bits of Q.
Applications:
Used in processors for efficient multiplication, especially in algorithms like Booth’s, which simplify
multiplication of signed binary numbers.