Introduction to Computer Org &
Architecture
What is a Computer?
A computer is an electronic device, operating under the control of instructions stored in its own
memory that can accept data (input), process the data according to specified rules, produce
information (output), and store the information for future use.
Why do we use Computers?
IT DOESN’T GET TIRED
!!
THE ABILITY TO WORK
ON PROJECTS WITH
AMAZING SPEED
RELIABILITY (LOW
FAILURE RATE)
VERY ACCURATE
ABLE TO STORE HUGE
AMOUNTS OF DATA
AND INFORMATION
ABLE TO
COMMUNICATE WITH
OTHER COMPUTERS
Computer Architecture
Computer architecture is the functional design and structure of a computer system. It focuses on
how a computer’s hardware components, like the CPU and memory, work together to execute
instructions efficiently. It involves decisions about the instruction set, data paths, and control
units to optimize performance and functionality.
Architecture describes what a computer does and serves as the blueprint for designing
computer systems. It is developed before computer organization during the system design
process.
Computer Organization
Computer organization focuses on the physical implementation of a computer system
based on its architecture. It deals with how different hardware components, like the CPU,
memory, and input/output devices, are connected and work together to execute tasks.
While computer architecture explains what a computer does, computer organization
describes how it does it.
Computer organization ensures the architectural design is translated into a functional,
physical system.
Computer Organization vs Architecture
Functions of a Computer
There are four basic functions that a computer can perform:
◦ Data processing
◦ Data may take a wide variety of forms and the range of processing requirements is broad
◦ Data storage
◦ Short-term
◦ Long-term
◦ Data movement
◦ Input-output (I/O) - when data are received from or delivered to a device (peripheral) that is directly
connected to the computer
◦ Data communications – when data are moved over longer distances, to or from a remote device
◦ Control
◦ A control unit manages the computer’s resources and orchestrates the performance of its functional parts in
response to instructions
COMPUTER
Main
memory
I/O
Computer Structure
System
Bus
•CPU – controls the operation of the computer and performs
CPU
CPU
Registers
Internal
Bus
Control
Unit
CONTROL
UNIT
Sequencing
Logic
Control Unit
Registers and
Decoders
Control
Memory
Figure 1.1 A Top-Down View of a Computer
ALU
its data processing functions
• Main Memory – stores data
• I/O – moves data between the computer and its external
environment
• System Interconnection – some mechanism that provides for
communication among CPU, main memory, and I/O
What does a CPU do?
The main function of a computer processor is to execute instructions and
produce an output. CPU work Fetch, Decode, and Execute are the
fundamental functions of the computer.
• Fetch: the first CPU gets the instruction. That means binary numbers that
are passed from RAM to CPU.
• Decode: When the instruction is entered into the CPU, it needs to decode
the instructions. with the help of ALU(Arithmetic Logic Unit), the process of
decoding begins.
• Execute: After the decode step the instructions are ready to execute.
• Store: After the execute step the instructions are ready to store in the
memory.
CPU Components
•Control Unit:
• Directs and coordinates CPU operations.
• Interprets instructions and manages data flow.
•Arithmetic Logic Unit (ALU):
• Executes arithmetic (addition, subtraction) and logical (AND, OR)
operations.
• The computational powerhouse of the CPU.
•Registers (Memory Units):
• Small, fast storage locations within the CPU.
• Hold instructions, data, and addresses for quick access.
•Interconnections:
• Buses and circuits that link the Control Unit, ALU, and Registers.
• Facilitate the efficient movement of data and control signals.
Single vs
Multi-core
Computer
Structure
•Single-Core Architecture
•One Processing Unit: Executes one instruction stream at a time.
•Sequential Processing: Limited multitasking; relies on rapid task switching.
•Simpler Design: Less complex, but with inherent performance limits.
•Clock Speed Dependent: Performance improvements mainly from increasing clock speed.
•Multicore Architecture
•Multiple Processing Units: Several cores on one chip work concurrently.
•Parallel Processing: Ideal for multitasking and multithreaded applications.
•Enhanced Performance: Distributes workload, improving efficiency and speed.
•Energy Efficiency: Often more power-efficient per task when handling parallel workloads.
•Complex Scheduling: Requires advanced OS and software support for optimal
performance.
Registers in CPU
Memory buffer register (MBR)
• Contains a word to be stored in memory or sent to the I/O unit
• Or is used to receive a word from memory or from the I/O unit
Memory address register (MAR)
• Specifies the address in memory of the word to be written from or read into the MBR
Instruction register (IR)
Instruction buffer register (IBR)
Program counter (PC)
Accumulator (AC) and multiplier
quotient (MQ)
• Contains the 8-bit opcode instruction being executed
• Employed to temporarily hold the right-hand instruction from a word in memory
• Contains the address of the next instruction pair to be fetched from memory
• Employed to temporarily hold operands and results of ALU operations
Main Memory (RAM –
Random Access Memory)
•Temporary Storage:
Stores data while the computer is running;
data is lost when the computer is turned off.
•Random Access:
Allows quick, direct access to any part of the
memory.
•Brain Analogy:
Similar to human brain memory, it helps
process and store essential information.
•Fast Processing:
Enables smooth program execution and rapid
data processing.
RAM vs Hard Drive storage
Input / Output (I/O): Internal vs External
•External I/O:
•Purpose: Facilitates communication between the computer and external devices.
•Examples: Keyboard, mouse, monitor, printer, scanner.
•Role: Enables user interaction by receiving input and delivering output.
•Internal I/O:
•Purpose: Manages data flow between internal components – i.e. system interconnection
•Examples: Communication between CPU, memory, storage devices, and internal controllers.
•Role: Ensures smooth and efficient data transfers within the system.
•Overall Importance:
•Integrates external interactions with internal processing.
•Critical for overall system performance and responsiveness.
External I/O
• What is I/O?
• The system for communication between a computer and
external devices.
• Input Devices:
• Examples: Keyboard, mouse, scanner.
• Purpose: Send data and commands into the computer.
• Output Devices:
• Examples: Monitor, printer, speakers.
• Purpose: Display or present processed data.
• Role of I/O:
• Bridges the gap between user commands and computer
processing.
• Ensures smooth data flow in and out of the system.
System
Interconnection
The network of connections that links various components of
a computer system, enabling data communication.
•Key Components:
•Buses & Interconnects: High-speed pathways (e.g.,
system bus, memory bus) that carry data and control
signals.
•Controllers & Switches: Manage data routing between
components like the CPU, memory, storage, and I/O
devices.
•Role in the System:
•Data Transfer: Ensures quick and efficient movement
of data and instructions between internal components.
•Coordination: Synchronizes operations across different
parts of the system to prevent bottlenecks.
•Performance Enhancement: A well-designed
interconnection architecture improves overall system
speed and responsiveness.
•Benefits:
•Efficiency: Streamlines internal communication.
•Scalability: Supports the integration of more
components or advanced technologies.
End of Lecture 
ANY QUESTIONS?