CHAP 9-10 Instruction sets, addressing modes,

and formats

1. Define a machine instruction and explain its key elements.

A machine instruction is a command that tells the processor what to do.
Key elements include:
o Opcode: Specifies the operation to perform.

o Source Operand: Provides data for the operation.

o Result Operand: Shows where to store the result.

o Next Instruction Reference: Points to the next command.

2. Describe the role of the opcode in a machine instruction.

The opcode (operation code) tells the processor which action to perform,
like add, subtract, or load data.
3. Differentiate between source operand and result operand
references in an instruction.
o Source Operand: Supplies input data for an operation.

o Result Operand: Shows where to store the result of the operation.

4. Explain the purpose of the instruction set and its significance for
a processor.
The instruction set is the collection of commands a processor can perform.
It defines what the processor can do and how it interacts with memory and
other parts of the computer.
5. How do three-address, two-address, and one-address instructions
differ? Provide examples.
o Three-Address: Uses three locations (e.g., ADD C = A + B).

o Two-Address: Uses two locations (e.g., ADD A = A + B).

o One-Address: Uses one location and a fixed memory spot (e.g.,

LOAD A).
6. Describe the main types of instructions used in a processor’s
instruction set.
o Data Processing: Like add, subtract.

o Data Storage: Storing data to memory.

o Data Movement: Moving data between places.

o Control: Changing instruction flow, like jumping to another

command.
7. Explain the difference between direct and indirect addressing.
 o Direct Addressing: The address of the data is given directly.

o Indirect Addressing: Points to an address that holds the actual

data’s address.
8. How does immediate addressing work, and what are its
advantages and disadvantages?
Immediate Addressing: The actual data is part of the instruction itself.
o Advantage: Fast, as no memory lookup is needed.

o Disadvantage: Limited data size due to fixed space.

9. Define register addressing and explain its main benefits and

limitations.
Register Addressing: Uses the CPU’s small, fast storage areas
(registers).
o Benefits: Quick access since no memory lookup is needed.

o Limitation: Limited space, as there are only a few registers.

10.What is displacement addressing, and in which situations is it

most commonly used?
Displacement Addressing: Combines a fixed address with a register
address to get the data’s location. It’s used for flexibility, like accessing
arrays in loops.
11.Explain how base-register addressing and indexing function. How
are they different?
 Base-Register Addressing: Uses a starting (base) address in memory
plus a small offset.
 Indexing: Uses an address plus an index to locate data, useful for
repetitive operations like arrays.
12.Describe the stack addressing mode and its primary application in
a computer system.
Stack Addressing Mode: Uses a Last-In-First-Out (LIFO) structure to
store data, like temporary calculations. It’s mainly used in function calls to
handle parameters and results.
13.Discuss the factors that influence the design of instruction
formats.
Factors include memory size, how data is stored and moved, processor
speed, and complexity of commands. Designers balance these to make
the processor efficient.
14.Explain the impact of instruction length on processor performance
and memory organization.
 Short Instructions: Faster, but may do less.
 Long Instructions: Can do more complex tasks but take longer to fetch
and use more memory.
 15.Describe the role of the program counter in relative addressing.
The program counter keeps track of the next instruction’s location. In
relative addressing, it helps calculate the address of the instruction to
execute next, useful in loops and conditional jumps.

CHAP 6 INPUT/OUTPUT
1. Explain the role of an I/O module in a computer system. What are
its primary functions?
o An I/O (Input/Output) module acts as a bridge between the CPU and
peripheral devices. Its primary functions include managing data
transfer between the computer’s internal components and external
devices, coordinating control signals, and ensuring proper data
transmission.
2. Describe the three categories of external devices and provide
examples for each category.
o The three categories of external devices are:

 Human-readable devices: Devices that provide information

in a form readable by humans, like monitors and printers.
 Machine-readable devices: Devices that interact with
other systems, like hard drives and sensors.
 Communication devices: Devices used for data transfer
between computers, such as network cards and modems.
3. Compare and contrast Programmed I/O, Interrupt-Driven I/O, and
Direct Memory Access (DMA) in terms of processor involvement
and efficiency.
o Programmed I/O: The CPU is heavily involved, manually
controlling data transfer, which can be inefficient for high data
rates.
o Interrupt-Driven I/O: The CPU only gets involved when it receives
an interrupt from the I/O device, which is more efficient than
Programmed I/O.
o DMA: The I/O module takes over data transfer, allowing the CPU to
perform other tasks. DMA is most efficient for large data transfers,
as it reduces CPU involvement.
4. List and explain the four types of I/O commands that an I/O
module can receive.
o Control command: Instructs the device to perform a specific
action.
o Test command: Checks if a device is available or operational.

o Read command: Transfers data from the device to the main

memory.
 o Write command: Sends data from the main memory to the device.

5. Discuss the difference between Memory-Mapped I/O and Isolated

I/O. What are the advantages and disadvantages of each
approach?
o Memory-Mapped I/O: I/O devices share memory addresses with
regular memory, simplifying the system but limiting address space.
o Isolated I/O: Uses separate address space for I/O, preserving
memory addresses but requiring additional instructions for
communication.
6. What are the limitations of Programmed I/O and Interrupt-Driven
I/O when dealing with high data transfer rates?
o Programmed I/O: Inefficient as it monopolizes the CPU for data
transfer tasks, unsuitable for high data rates.
o Interrupt-Driven I/O: Better than Programmed I/O but still causes
delays due to CPU involvement, which can be problematic at very
high data rates.
7. Describe how Direct Cache Access (DCA) is used to handle high
data transfer demands and how it differs from Direct Memory
Access (DMA).
o DCA: Transfers data directly into the CPU cache, reducing memory
access time and improving speed. Unlike DMA, DCA places data
closer to the CPU for faster processing.
o DMA: Transfers data to main memory, where the CPU accesses it
later, making it slightly slower than DCA.
8. Outline the evolution of the Universal Serial Bus (USB) and
compare the data rates provided by USB 1.0, USB 2.0, USB 3.0,
and USB 3.1.
o USB 1.0: Introduced at 1.5 Mbps and 12 Mbps for Low-Speed and
Full-Speed modes.
o USB 2.0: Improved to 480 Mbps (High-Speed).

o USB 3.0: Increased to 5 Gbps (SuperSpeed).

o USB 3.1: Boosted to 10 Gbps (SuperSpeed+), supporting higher

speeds for data transfer and faster charging.
9. Explain the concept of PCI Express (PCIe) and Serial Advanced
Technology Attachment (SATA). How are these technologies used
in connecting peripherals?
o PCIe: A high-speed interface for connecting devices like graphics
cards and network cards directly to the motherboard.
o SATA: Primarily connects storage devices like hard drives and SSDs
to the motherboard, offering reliable data transfer.
10.Discuss the importance of Ethernet as a networking technology.
How has it evolved to meet the demands of modern networks?
o Ethernet is essential for wired networking, providing a stable and
fast connection. Over time, Ethernet has evolved from slower
speeds (10 Mbps) to high-speed gigabit (1 Gbps) and even 10 Gbps
options, supporting higher data demands in modern networks.
11.Explain how Wi-Fi technology has transformed Internet access in
both public and enterprise environments. What are the benefits of
modern Wi-Fi standards?
o Wi-Fi enables wireless internet access, offering mobility and
convenience in homes, offices, and public spaces. Modern standards
like Wi-Fi 6 provide faster speeds, reduced congestion, and
improved performance in crowded environments, transforming how
people connect and access data.