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Computer Systems 💻 (The Internet & Networks (Network Types (WAN (Wide…

- - - - Routes packets across a WAN. Packets are passed from router to destination.
    - - Forwards the packets only to the intended recipient using its MAC address.
    - - Network Interface Card
      - Required to connect a network-enabled device
  - - - Can be costly to install
      - If cnetral server fails, whole network does
      - If one cable fails the other workstations are not affected.
      - Consistent performance if when network is heavily used.
    - - Very expensive cabling
      - Difficult to install
      - Every node has a connection to every other
      - Easy to add nodes
      - If one route fails, there are others available
  - - - A subset of computers connected together as part of a larger physical network.
    - - Almost all Wi-Fi installations use the 2.4GHz or 5GHz band, operating at these frequencies. These are divided into overlappying channels, and with a centred frquency and bandwidth.
    - - Local Area Network
      - Over a relatively small geographical area
    - - Wide Area Network
      - Over a large geographical area
      - E.g. the internet
    - - Wi-Fi
        
        Wireless Fidelity
        
        No physical wires
      - Risks
        
        Criminal Activity
        
        Bandwidth stealing
        
        Confidentiality
      - WAPs
        
        Wireless Access Points
        
        Emits and recieves radio waves converted into data for physical connection.
  - - - Internet Protocol
      - Every device on a network has a unique IP address for information transfer.
    - - URL as we know them are stored on a domain name server
      - When URLs are entered, they are referenced to an IP.
    - - Each NIC has a media access control address
      - Media Access Control Address
      - 48-bit address written in hexadecimal
  - - - UTP
        
        Made Of Copper
        
        Fast data transmission
        
        Minimal interference
        
        Thin & Flexible
        
        Unshielded Twisted Pair
      - Fibre Optic
        
        Long distance
        
        Light is transmitted along glass fibres
        
        Total internal reflection keeps losses to a minimum
        
        Not subject to interference
        
        Does not deteriorate in exposed locations
      - Coaxial
        
        Bulky compared to UTP
        
        Less convenient to install
- - - - Info lost upon losing power.
      - E.g. RAM
    - - Info retained upon losing power
      - E.g. ROM, Hard Disk
  - - - Laser writes/reads from a disc
      - Comes as read-only, recordable or rewritable
      - Good for distribution (CDs, DVDs)
      - Comparatively low capacity
      - Easy to break
    - - No moving parts
      - Referred to as flash memory
      - Reliable
      - Light
      - Fast
    - - Read with a moving head inside disk drive
      - Moving parts slow it down
      - Vulnerable to magnetic fields
      - Large Capacity
  - - - Capacity
      - Speed
      - Portability
      - Durability
      - Reliability
      - Cost
- - - - Memory Address Register - Holds address of instruction that is to be fetched or stored.
    - - Memory Data Register - The data of program instruction that is fetched from memory is temporarily stored here.
    - - Holds memory address of the next instruction to be processed, incrementing by 1 each time.
    - - Arithmetic Logic Unit - Carries out logical, shift and arithmetic operations.
    - - Executes, decodes, regulates, & sends/receives control signals.
    - - Current Instruction Register - Holds the current instruction which has been fetched.
    - - Holds the result of all calculations