3.1 The Central Processing Unit & Architecture
3.1.1 The Central Processing Unit (CPU)
The CPU is the "brain" of the computer, responsible for executing instructions and performing calculations. It consists of several key components:
Key Components:
- Arithmetic Logic Unit (ALU) - Performs mathematical and logical operations
- Control Unit (CU) - Manages instruction execution and coordinates other components
- Registers - High-speed storage locations for immediate data access
3.1.2 Von Neumann Architecture
The Von Neumann architecture is the foundation of modern computers, featuring:
Core Principles:
- Stored Program Concept - Both data and instructions are stored in the same memory
- Single Bus System - One pathway for data and instructions
- Sequential Execution - Instructions processed one at a time
Fetch-Decode-Execute Cycle Demo
Click the button to see the CPU cycle in action:
FETCH
Get instruction from memory
DECODE
Interpret the instruction
EXECUTE
Perform the operation
3.1.3 Cores, Cache and Internal Clock
Multi-Core Processing:
- Single Core - One processing unit
- Multi-Core - Multiple processing units on one chip
- Advantages - Parallel processing, better performance
Cache Memory:
- L1 Cache - Fastest, smallest, built into CPU
- L2 Cache - Larger than L1, shared between cores
- L3 Cache - Largest, shared by all cores
Clock Speed:
- Measured in Hz - Cycles per second
- Higher = Faster - More instructions per second
- Heat Generation - Faster clocks produce more heat
3.1.4 Instruction Set
The instruction set is the collection of commands a CPU can understand and execute:
Types of Instructions:
- Data Transfer - Move data between locations (LOAD, STORE)
- Arithmetic - Mathematical operations (ADD, SUB, MUL)
- Logic - Boolean operations (AND, OR, NOT)
- Control Flow - Program flow control (JUMP, BRANCH)
3.1.5 Embedded Systems
Specialized computer systems designed for specific tasks:
Characteristics:
- Purpose-Built - Designed for specific applications
- Resource Constrained - Limited memory and processing power
- Real-Time Operation - Must respond within strict time limits
- Examples - Car ECUs, smart appliances, IoT devices
3.3 Data Storage
3.3.1 Primary Memory
Primary memory provides direct access to the CPU and includes:
RAM
Random Access Memory - Volatile, fast access
ROM
Read-Only Memory - Non-volatile, permanent storage
Cache
Ultra-fast temporary storage
RAM Types:
- DRAM - Dynamic RAM, needs refreshing
- SRAM - Static RAM, faster but more expensive
- DDR - Double Data Rate, transfers on both clock edges
3.3.2 Secondary and Offline Storage
Non-volatile storage for long-term data retention:
Secondary Storage:
- Hard Disk Drives (HDDs) - Magnetic storage, high capacity
- Solid State Drives (SSDs) - Flash memory, fast access
- Optical Drives - CDs, DVDs, Blu-ray discs
Offline Storage:
- Tape Drives - Sequential access, archival storage
- External Drives - Portable storage solutions
- Network Attached Storage - Shared storage over network
3.3.3 Magnetic, Optical and Solid-State Storage
Magnetic
HDDs, tape drives
High capacity, slower access
Optical
CDs, DVDs, Blu-ray
Portable, read-only or rewritable
Solid-State
SSDs, flash drives
Fast access, no moving parts
3.3.4 Virtual Memory
Virtual memory extends available memory by using secondary storage:
Key Concepts:
- Paging - Memory divided into fixed-size pages
- Swapping - Moving data between RAM and disk
- Virtual Address Space - Logical memory addresses
- Benefits - Multitasking, memory protection, larger address space
3.3.5 Cloud Storage
Remote storage accessed via the internet:
Advantages:
- Accessibility - Access from anywhere with internet
- Scalability - Easily increase storage capacity
- Backup - Automatic data redundancy
- Cost-Effective - Pay for what you use
Considerations:
- Internet Dependency - Requires stable connection
- Security - Data stored on third-party servers
- Latency - Network delays affect access speed
3.4 Network Hardware
3.4.1 Network Interface Cards (NICs)
Hardware components that connect devices to networks:
Ethernet NIC
Wired network connection
Wi-Fi Adapter
Wireless network connection
Integrated NIC
Built into motherboard
Functions:
- Physical Connection - Provides network interface
- Data Conversion - Digital to network signals
- MAC Address - Unique hardware identifier
- Protocol Handling - Manages network protocols
3.4.2 Media Access Control (MAC) Addresses
Unique identifiers for network interfaces:
Characteristics:
- 48-bit Address - Usually shown as 12 hex digits
- Globally Unique - No two devices have the same MAC
- Hardware Level - Burned into network interface
- Format - XX:XX:XX:XX:XX:XX (e.g., 00:1B:44:11:3A:B7)
MAC Address Demo
Click to generate a MAC address
3.4.3 Internet Protocol (IP) Addresses
Logical addresses used for routing data across networks:
IPv4 Addresses:
- 32-bit Address - Four octets (e.g., 192.168.1.1)
- Classes - Class A, B, C for different network sizes
- Public vs Private - Internet-routable vs local network
- Subnetting - Dividing networks into smaller segments
IPv6 Addresses:
- 128-bit Address - Eight groups of hex digits
- Larger Address Space - Solves IPv4 exhaustion
- Auto-configuration - Devices can self-assign addresses
- Format - 2001:0db8:85a3:0000:0000:8a2e:0370:7334
3.4.4 Routers
Network devices that forward data between different networks:
Functions:
- Packet Forwarding - Routes data to destination networks
- Path Selection - Determines best route for data
- Network Segmentation - Separates broadcast domains
- Protocol Translation - Connects different network types
Types:
- Home Routers - Connect home networks to internet
- Enterprise Routers - Handle large-scale network traffic
- Core Routers - Backbone internet infrastructure
- Wireless Routers - Combine routing with Wi-Fi access
Practice Quiz
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