⌨️AP Computer Science Principles Unit 4 – Computer Systems & Networks

Key Concepts

• Computer systems consist of hardware, software, and data that work together to perform specific tasks and solve problems
• Networks enable computer systems to communicate and share resources (data, devices, services) with each other
• Data transmission involves sending digital data over a communication channel from a sender to a receiver
• Protocols are sets of rules that govern how devices communicate and exchange data over a network
• Network security measures protect computer systems and data from unauthorized access, use, disclosure, disruption, modification, or destruction
• Troubleshooting is the systematic process of identifying, diagnosing, and resolving problems in computer systems and networks
  • Involves gathering information, analyzing symptoms, identifying potential causes, and implementing solutions
• Computer systems and networks have numerous real-world applications across various industries (healthcare, education, finance, entertainment)

System Components

• Hardware refers to the physical components of a computer system that can be touched (motherboard, CPU, RAM, storage devices)
• Software is a set of instructions that tells the hardware what to do and how to perform specific tasks
  • Includes operating systems (Windows, macOS, Linux), applications, and utilities
• Data is the information processed, stored, and transmitted by computer systems
  • Can be in various forms such as text, numbers, images, audio, and video
• Input devices allow users to enter data and commands into a computer system (keyboard, mouse, touchscreen, microphone)
• Output devices present information to users from a computer system (monitor, printer, speakers)
• Processing devices perform computations and execute instructions (CPU, GPU)
• Storage devices retain data and programs for future use (hard disk drives, solid-state drives, USB flash drives, optical discs)

Network Fundamentals

• A network is a group of interconnected devices that can communicate and share resources with each other
• Network topology refers to the arrangement and layout of devices and connections in a network
  • Common topologies include bus, star, ring, mesh, and tree
• Network types can be classified based on size, geographical coverage, and ownership
  • Local Area Network (LAN) covers a small area (home, office, school)
  • Wide Area Network (WAN) spans a large geographical area (cities, countries, continents)
• Network devices facilitate communication and data transfer between connected devices
  • Switches connect devices within a network and forward data packets to the intended destination
  • Routers connect multiple networks and determine the best path for data packets to reach their destination
• Network media refers to the physical channels used to transmit data between devices
  • Wired media includes coaxial cables, twisted pair cables, and fiber optic cables
  • Wireless media uses radio waves to transmit data (Wi-Fi, Bluetooth, cellular networks)

Data Transmission

• Data transmission is the process of sending digital data from one device to another over a communication channel
• Bandwidth refers to the maximum amount of data that can be transmitted over a channel in a given period of time
  • Measured in bits per second (bps), kilobits per second (Kbps), megabits per second (Mbps), or gigabits per second (Gbps)
• Latency is the time delay between the sender transmitting data and the receiver receiving it
  • Measured in milliseconds (ms) or seconds (s)
• Packet switching is a method of transmitting data over a network by breaking it into smaller units called packets
  • Each packet contains a source address, destination address, and a portion of the data being sent
• Circuit switching is a method of transmitting data over a network by establishing a dedicated communication channel between the sender and receiver
  • Commonly used in traditional telephone networks
• Multiplexing techniques allow multiple signals or data streams to be combined and transmitted over a single communication channel
  • Time-division multiplexing (TDM) allocates time slots to each data stream
  • Frequency-division multiplexing (FDM) assigns different frequency bands to each data stream

Protocols and Standards

• Protocols are sets of rules and conventions that govern how devices communicate and exchange data over a network
• The Open Systems Interconnection (OSI) model is a conceptual framework that standardizes communication functions in a network
  • Consists of seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application
• The Transmission Control Protocol/Internet Protocol (TCP/IP) is a suite of protocols used in computer networks and the Internet
  • Consists of four layers: Network Access, Internet, Transport, and Application
• Hypertext Transfer Protocol (HTTP) is an application-layer protocol used for transmitting web pages and other content over the Internet
• File Transfer Protocol (FTP) is an application-layer protocol used for transferring files between computers over a network
• Simple Mail Transfer Protocol (SMTP) is an application-layer protocol used for sending and receiving email messages
• Domain Name System (DNS) is a hierarchical naming system that translates human-readable domain names into IP addresses
• Standards organizations develop and maintain protocols and standards to ensure interoperability between devices and networks
  • Examples include the Internet Engineering Task Force (IETF), Institute of Electrical and Electronics Engineers (IEEE), and International Organization for Standardization (ISO)

Security and Privacy

• Network security involves protecting computer systems, networks, and data from unauthorized access, use, disclosure, disruption, modification, or destruction
• Confidentiality ensures that data is accessible only to authorized users and is protected from unauthorized disclosure
  • Achieved through encryption, access controls, and secure communication channels
• Integrity ensures that data remains accurate, complete, and unaltered during transmission and storage
  • Achieved through error detection and correction, digital signatures, and hashing algorithms
• Availability ensures that data and resources are accessible to authorized users when needed
  • Achieved through redundancy, backup systems, and disaster recovery plans
• Authentication is the process of verifying the identity of a user or device before granting access to resources
  • Achieved through usernames and passwords, biometric data, digital certificates, and multi-factor authentication
• Authorization is the process of granting or denying access to resources based on a user's authenticated identity and permissions
  • Achieved through access control lists (ACLs), role-based access control (RBAC), and attribute-based access control (ABAC)
• Firewalls are security devices that monitor and control incoming and outgoing network traffic based on predetermined security rules
  • Can be hardware-based or software-based
• Virtual Private Networks (VPNs) create secure, encrypted connections over public networks (Internet) to protect data privacy and integrity

Troubleshooting and Maintenance

• Troubleshooting is the systematic process of identifying, diagnosing, and resolving problems in computer systems and networks
• The first step in troubleshooting is to gather information about the problem, including symptoms, error messages, and any recent changes to the system
• Next, analyze the information collected to identify potential causes of the problem
  • Use a process of elimination to narrow down the list of possible causes
• Once the root cause is identified, implement a solution to resolve the problem
  • This may involve updating software, replacing hardware components, or modifying configuration settings
• After implementing the solution, test the system to ensure that the problem has been resolved and no new issues have been introduced
• Document the troubleshooting process, including the problem description, steps taken, and the resolution for future reference
• Preventive maintenance involves regularly scheduled tasks to keep computer systems and networks running smoothly and prevent potential problems
  • Includes updating software, cleaning hardware components, and performing data backups
• Monitoring tools and techniques help detect and diagnose problems before they cause significant disruptions
  • Examples include network monitoring software, system logs, and performance metrics

Real-World Applications

• Healthcare: Computer systems and networks enable electronic health records (EHRs), telemedicine, and medical imaging
  • Facilitates efficient patient care, improves diagnostic accuracy, and enhances collaboration among healthcare providers
• Education: Computer systems and networks support online learning platforms, educational resources, and collaborative tools
  • Enables distance learning, personalized instruction, and access to a wide range of educational materials
• Finance: Computer systems and networks are critical for electronic trading, online banking, and secure financial transactions
  • Ensures fast, reliable, and secure processing of financial data and reduces the risk of fraud and errors
• Entertainment: Computer systems and networks power streaming services (Netflix, Spotify), online gaming, and social media platforms
  • Provides users with on-demand access to a vast library of content and enables interactive experiences and social connections
• Transportation: Computer systems and networks enable intelligent transportation systems, GPS navigation, and autonomous vehicles
  • Improves traffic management, enhances safety, and optimizes route planning and logistics
• Manufacturing: Computer systems and networks support computer-aided design (CAD), computer-aided manufacturing (CAM), and industrial automation
  • Increases production efficiency, reduces costs, and improves product quality and consistency
• E-commerce: Computer systems and networks are the backbone of online marketplaces (Amazon, eBay) and digital payment systems
  • Enables businesses to reach a global customer base, streamlines transactions, and facilitates secure online payments