Computer
Architecture
·
Computer
Architecture is the design and organization of a computer system that describes
how different components of a computer work together to perform tasks.
·
It
defines the structure, functionality, and interaction of hardware components
such as the CPU, memory, input/output devices, and storage systems.
·
Computer
architecture acts as a blueprint that explains how instructions are processed
and how data flows within a computer.
Main
Components of Computer Architecture
1.
Central
Processing Unit (CPU)
·
The
CPU is the main processing unit of a computer.
·
It
executes instructions and controls all operations.
·
It
consists of:
§ Arithmetic Logic Unit
(ALU):
ü Performs arithmetic
operations such as addition, subtraction, multiplication, and division.
ü Performs logical
operations such as comparison and decision-making.
§ Control Unit (CU):
ü Controls and
coordinates all activities of the computer.
ü Manages the flow of
data between CPU, memory, and input/output devices.
§ Registers: Small,
high-speed storage locations inside the CPU.
2.
Memory
Unit
§ Stores data,
instructions, and results temporarily or permanently.
§ Includes:
1.
Primary
Memory: RAM and ROM.
2.
Secondary
Memory: Hard drives, SSDs, and other storage devices.
3.
Input
Unit
·
Allows
users to enter data and instructions into the computer.
·
Examples:
Keyboard, mouse, scanner.
4.
Output
Unit
·
Displays
processed information to users.
·
Examples:
Monitor, printer, speakers.
5.
System
Bus
·
A
communication pathway that transfers data, instructions, and signals between
computer components.
Importance
of Computer Architecture
·
Determines
the speed and performance of a computer.
·
Helps
in designing efficient computer systems.
·
Improves
hardware and software compatibility.
·
Defines
how data is processed and stored.
Registers
·
Registers
are small, high-speed storage locations inside the CPU used to temporarily
store data, instructions, and addresses during processing.
·
They
provide faster access to information compared to main memory (RAM).
·
Registers
help the CPU perform calculations, execute instructions, and control computer
operations efficiently.
·
The
size and number of registers affect the performance and speed of a processor.
·
Used
in computers, smartphones, and other digital devices to improve processing
speed.
Types
of Registers
1.
Accumulator (ACC)
•
Stores
intermediate results of arithmetic and logical operations.
•
Helps
the CPU perform calculations quickly.
•
Used
frequently by the Arithmetic Logic Unit (ALU).
2.
Program Counter (PC)
•
Stores
the address of the next instruction to be executed.
•
Helps
the CPU execute instructions in the correct sequence.
•
Automatically
updates after each instruction is processed.
3.
Instruction Register (IR)
•
Holds
the current instruction being executed by the CPU.
•
Helps
the control unit decode and process instructions.
•
Ensures
proper execution of program commands.
4.
Memory Address Register (MAR)
•
Stores
the address of the memory location to be accessed.
•
Helps
the CPU locate data or instructions in memory.
•
Used
during read and write operations.
5.
Memory Data Register (MDR)
•
Stores
data being transferred to or from memory.
•
Acts
as a temporary storage area during memory operations.
•
Helps
transfer information between CPU and memory.
6.
General Purpose Registers (GPR)
•
Store
temporary data and intermediate results during processing.
•
Can
be used for various operations by programs.
•
Improve
the efficiency of CPU operations.
Memory
Management
•
Memory
management is the process of controlling and organizing the computer's main
memory (RAM) by the operating system.
•
It
manages the allocation and deallocation of memory space to different programs
and processes.
•
Ensures
that programs get enough memory to run efficiently and prevents memory
conflicts.
•
Improves
system performance by using memory resources effectively.
•
Handles
tasks such as memory allocation, memory protection, and virtual memory
management.
Functions
of Memory Management
1.
Memory Allocation
•
Assigns
memory space to programs and processes when they need it.
•
Ensures
efficient use of available memory resources.
•
Releases
memory when a program finishes execution.
2.
Memory Deallocation
•
Removes
unused memory from completed processes.
•
Makes
memory available for other programs.
•
•Prevents
unnecessary memory usage.
3.
Memory Protection
•
Prevents
one process from accessing another process's memory without permission.
•
Maintains
security and stability of the system.
•
Protects
important operating system data.
4.
Virtual Memory Management
•
Uses
a portion of secondary storage as an extension of RAM.
•
Allows
larger programs to run even when physical memory is limited.
•
Improves
multitasking capability of the computer.
5.
Address Translation
•
Converts
logical addresses generated by programs into physical memory addresses.
•
Helps
the CPU access the correct memory location.
•
Managed
using techniques such as paging and segmentation.
Types
of Memory Management Techniques
1.
Paging
•
Divides
memory into fixed-size blocks called pages and frames.
•
Allows
efficient use of memory and reduces external fragmentation.
•
Commonly
used in modern operating systems.
2.
Segmentation
•
Divides
memory into variable-sized segments based on program structure.
•
Helps
organize programs into logical parts such as code, data, and stack.
•
Provides
better memory organization.
3.
Swapping
•
Temporarily
moves processes between RAM and secondary storage.
•
Helps
manage limited memory resources.
•
Allows
multiple programs to run simultaneously.
Importance
of Memory Management
•
Improves
computer performance and speed.
•
Allows
multiple programs to run at the same time.
•
Prevents
memory wastage and conflicts.
•
Provides
security and efficient use of memory resources.
Types
of Computer Memory
Computer
memory is divided into two main categories: Primary Memory and Secondary
Memory.
1.
Primary Memory (Main Memory)
•
Primary
memory is the main storage area directly accessed by the CPU.
•
It
stores data and instructions that are currently being processed.
•
It
is faster than secondary memory but has limited storage capacity.
Types
of Primary Memory
a.
RAM (Random Access Memory)
•
RAM
is a temporary (volatile) memory used to store data and programs currently in
use.
•
Data
is lost when the computer is turned off.
•
Examples
include Dynamic RAM (DRAM) and Static RAM (SRAM).
b.
ROM (Read Only Memory)
•
ROM
is a permanent (non-volatile) memory that stores important instructions.
•
Data
remains stored even when power is turned off.
•
Used
to store firmware and boot instructions.
c.
Cache Memory
•
Cache
is a high-speed memory located near or inside the CPU.
•
Stores
frequently used data and instructions for faster access.
•
Improves
the overall performance of the computer.
d.
Registers
•
Registers
are the fastest memory units located inside the CPU.
•
Temporarily
store data, instructions, and processing results.
•
Help
the CPU execute operations quickly.
2.
Secondary Memory (Auxiliary Memory)
•
Secondary
memory is used for permanent storage of data and programs.
•
It
has larger storage capacity but is slower than primary memory.
•
Data
remains stored even when the power is turned off.
Types
of Secondary Memory
a.
Hard Disk Drive (HDD)
•
Stores
large amounts of data permanently.
•
Uses
magnetic storage technology.
•
Commonly
used for operating systems, software, and files.
b.
Solid State Drive (SSD)
•
Uses
flash memory to store data.
•
Faster
and more reliable than traditional hard disks.
•
Commonly
used in modern computers and laptops.
c.
Optical Storage
•
Stores
data using laser technology.
•
Examples
include CDs, DVDs, and Blu-ray discs.
•
Used
for media storage and data backup.
d.
USB Flash Drive
•
A
portable storage device used to transfer and store data.
•
Uses
flash memory technology.
•
Provides
convenient data storage and sharing.
e.
Memory Card
•
A
small portable storage device used in cameras, smartphones, and other devices.
•
Provides
additional storage capacity.
•
Examples
include SD cards and microSD cards.
Organization
of Hard Disk
•
A
hard disk is organized into several parts that work together to store and
retrieve data efficiently.
•
Data
is stored magnetically on rotating platters and accessed by read/write heads.
•
The
organization of a hard disk helps the operating system locate and manage stored
files.
Components
of Hard Disk Organization
1.
Platters
•
Platters
are circular magnetic disks where data is permanently stored.
•
A
hard disk may contain one or more platters.
•
Both
sides of each platter can store data.
2.
Tracks
•
Tracks
are concentric circular paths on the surface of a platter.
•
Data
is written and read along these circular paths.
•
Each
platter surface contains many tracks.
3.
Sectors
•
Sectors
are small divisions of a track used to store data.
•
Each
sector stores a fixed amount of data, usually 512 bytes or 4096 bytes (4 KB).
•
Sectors
are the smallest physical storage units on a hard disk.
4.
Clusters
•
A
cluster is a group of one or more sectors.
•
The
operating system stores files in clusters instead of individual sectors.
•
Larger
files occupy multiple clusters.
5.
Cylinder
•
A
cylinder is formed by tracks of the same position on all platters.
•
It
allows faster data access without moving the read/write head to another track.
•
Cylinders
help organize data across multiple platters.
6.
Read/Write Head
•
A
read/write head reads data from and writes data to the platter surface.
•
Each
platter surface has its own read/write head.
•
The
heads move across the platters to access different tracks.
7.
Spindle
•
The
spindle holds the platters together and rotates them at high speed.
•
Common
speeds are 5400 RPM and 7200 RPM.
•
Faster
rotation provides quicker data access.
Importance
of Hard Disk Organization
•
Enables
efficient storage and retrieval of data.
•
Improves
file management and disk performance.
•
Reduces
the time required to access stored information.
•
Supports
reliable and organized data storage.
Working
of Hard Disk
•
The
platter rotates at high speed using the spindle.
•
The
read/write head moves over the platter surface.
•
The
head reads data from or writes data to specific tracks and sectors.
•
The
disk controller manages the data transfer between the hard disk and computer.
CPU
Architecture
•
CPU
(Central Processing Unit) architecture refers to the design and organization of
the internal components of a processor.
•
It
defines how the CPU processes instructions, manages data, and communicates with
other computer components.
•
CPU
architecture determines the speed, performance, and efficiency of a computer
system.
•
It
includes components such as the Control Unit, Arithmetic Logic Unit, Registers,
and Cache Memory.
•
Modern
CPUs use advanced architectures to perform multiple operations quickly and
efficiently.
Components
of CPU Architecture
1.
Control Unit (CU)
•
Controls
and coordinates all activities of the CPU.
•
Fetches
instructions from memory and decodes them for execution.
•
Manages
the flow of data between CPU, memory, and input/output devices.
2.
Arithmetic Logic Unit (ALU)
•
Performs
arithmetic operations such as addition, subtraction, multiplication, and
division.
•
Performs
logical operations such as comparisons and decision-making.
•
Processes
data according to instructions provided by the Control Unit.
3.
Registers
•
Small
and high-speed storage locations inside the CPU.
•
Temporarily
store data, instructions, and intermediate results.
•
Help
the CPU execute instructions faster.
4.
Cache Memory
•
A
high-speed memory located inside or near the CPU.
•
Stores
frequently used data and instructions.
•
Reduces
the time needed to access information from main memory.
5.
Buses
•
Buses
are communication pathways that transfer data between CPU and other components.
•
Data
Bus transfers actual data.
•
Address
Bus carries memory addresses.
•
Control
Bus carries control signals.
CPU
Instruction Cycle
1.
Fetch
•
The
CPU retrieves an instruction from memory.
•
The
address of the instruction is stored in the Program Counter (PC).
2.
Decode
•
The
Control Unit interprets the instruction.
•
Determines
what operation needs to be performed.
3.
Execute
•
The
CPU performs the required operation using the ALU or other components.
•
Results
are stored in registers or memory.
4.
Store
•
The
result of the operation is saved for future use.
Types
of CPU Architecture
1.
Von Neumann Architecture
•
Uses
a single memory unit to store both data and instructions.
•
Data
and instructions are transferred through the same bus.
•
Works
on the fetch-decode-execute cycle.
•
It
is simple, cost-effective, and widely used in general-purpose computers.
•
A
limitation is the Von Neumann bottleneck, where data and instructions compete
for the same memory path.
•
Used
in desktop computers, laptops, and many general-purpose systems.
2.
Harvard Architecture
•
Uses
separate memory units for data and instructions.
•
Has
separate buses for transferring data and instructions.
•
Allows
data and instructions to be accessed simultaneously.
•
Provides
faster processing compared to Von Neumann architecture.
•
Commonly
used in microcontrollers, embedded systems, and digital signal processors.
3.
RISC Architecture (Reduced Instruction Set Computer)
•
Uses
a small set of simple instructions.
•
Instructions
are executed quickly, usually in a single clock cycle.
•
Requires
fewer transistors and provides high efficiency.
•
Uses
more registers to improve performance.
•
Examples:
ARM processors used in smartphones and tablets.
4.
CISC Architecture (Complex Instruction Set Computer)
•
Uses
a large set of complex instructions.
•
A
single instruction can perform multiple operations.
•
Reduces
the number of instructions needed to complete a task.
•
Requires
more hardware complexity.
•
Examples:
x86 processors used in personal computers.
Difference
Between RISC and CISC
RISC CISC
Uses
fewer and simpler instructions Uses
many complex instructions
Faster
execution of instructions Instructions
may take more cycles
Uses
more registers Uses
fewer registers compared to RISC
Lower
power consumption Higher
power consumption
Example:
ARM Example:
x86
I/O
Management
•
I/O
(Input/Output) Management is the function of an operating system that controls
and manages communication between the CPU, memory, and input/output devices.
•
It
provides a standard way for applications to interact with hardware devices.
•
Ensures
efficient data transfer between the computer and external devices.
•
Manages
device allocation, device drivers, buffering, and error handling.
•
Improves
the performance and reliability of input/output operations.
Functions
of I/O Management
1.
Device Control
•
Controls
and coordinates the operation of input and output devices.
•
Sends
commands to devices through device drivers.
•
Ensures
devices work properly with the operating system.
2.
Device Scheduling
•
Determines
the order in which I/O requests are processed.
•
Reduces
waiting time and improves system performance.
•
Manages
multiple requests from different programs.
3.
Buffering
•
Uses
temporary memory areas to store data during transfer.
•
Helps
match the speed difference between CPU and I/O devices.
•
Improves
efficiency of data transfer operations.
4.
Error Handling
•
Detects
and manages errors during I/O operations.
•
Reports
device failures and communication problems.
•
Helps
maintain system reliability.
I/O
Interface
•
An
I/O Interface is a hardware or software connection between the CPU and
input/output devices.
•
It
allows communication and data exchange between the computer system and external
devices.
•
Converts
signals and data formats so devices can communicate with the CPU.
•
Provides
control signals, status information, and data transfer mechanisms.
Components
of I/O Interface
1.
Data Register
•
Stores
data being transferred between CPU and I/O devices.
•
Acts
as a temporary storage area during communication.
2.
Status Register
•
Stores
information about the current condition of an I/O device.
•
Indicates
whether a device is ready, busy, or has an error.
3.
Control Register
•
Stores
commands and control information sent to devices.
•
Helps
the CPU manage device operations.
I/O
Requests Handling
•
I/O
request handling is the process of managing requests made by programs to
perform input or output operations.
•
The
operating system manages these requests using device drivers and I/O
controllers.
Steps
of I/O Request Handling
1.
Request Generation
•
A
program sends an I/O request to the operating system.
•
The
request specifies the required operation and device.
2.
Request Processing
•
The
operating system checks the request and identifies the required device.
•
It
communicates with the device driver to perform the operation.
3.
Device Operation
•
The
device controller performs the requested input or output task.
•
Data
is transferred between the device and memory.
4.
Completion and Notification
•
The
device sends a signal when the operation is completed.
•
The
operating system informs the requesting program about the result.
I/O
Devices
•
I/O
devices are hardware components used to provide input to and receive output
from a computer system.
•
They
allow users and computers to communicate with each other.
Types
of I/O Devices
1.
Input Devices
•
Used
to enter data and instructions into a computer.
•
Convert
user actions into digital signals.
•
Examples:
Keyboard, mouse, scanner, microphone, webcam.
2.
Output Devices
•
Used
to display or produce processed information.
•
Convert
digital data into a human-readable form.
•
Examples:
Monitor, printer, speakers, projector.
3.
Storage Devices
•
Used
to store and retrieve data permanently or temporarily.
•
Provide
additional storage capacity for computers.
•
Examples:
Hard disk, SSD, USB flash drive, memory card.
Importance
of I/O Management
•
Provides
communication between CPU and external devices.
•
Improves
speed and efficiency of data transfer.
•
Allows
multiple devices to work together smoothly.
•
Ensures
proper control and error handling of I/O operation.