Z notes

• Data Representation:

  • Denary (Base 10) uses integer digits
  • Binary (Base 2) uses 0 and 1, with all data and characters represented in binary
  • Binary Coded Decimal (BCD) represents each positive denary digit with a sequence of 4 bits (nibble)
• Two's Complement:

  • Represents negative numbers in binary by making the most significant bit (MSB) a sign bit
  • To convert a negative denary into binary, find the binary equivalent, add extra 0 bits before the MSB, flip the bits, and add 1
• Hexadecimal Systems:

  • Base 16 system with digits 0-9 and A-F
  • Practical applications include defining colors in HTML and MAC addresses
• Character Sets:

  • Include upper & lower case letters, number digits, punctuation marks, and other characters
  • Character encoding standards include ASCII, Extended ASCII, and Unicode
• Bitmap Images:

  • Data encoded by assigning a color to each pixel
  • Image resolution is measured by pixel density, affecting sharpness and detail
• Vector Graphics:

  • Made up of drawing objects defined mathematically
  • Properties of each object determine the shape and appearance, encoded using mathematical formulas
• Sound:

  • Analogue data is continuous electrical signals, digital data is discrete
  • Sound signals are vibrations through a medium, converted to digital signals by sampling
• Compression:

  • Lossless compression allows perfect reconstruction of original data
  • Lossy compression eliminates unnecessary data irreversibly, reducing file size with lower quality
• Networking:

  • LAN connects devices within a small area, WAN within a larger area
  • Client-server model involves a dedicated server providing applications for client computers
• Thin Clients vs. Thick Clients:

  • Thin clients solely run on server resources, while thick clients are independent and do not require the server to run
• Peer-to-peer network model (P2P):

  • Decentralized network where each connected computer stores data and operates independently as a 'peer'
• Client-server vs. Peer-to-peer models:

  • Client-server offers centralized backup and improved security, while Peer-to-peer has lesser initial setup cost and lesser network traffic
• A computer network can be set up in different topologies like Bus, Star, Mesh, or Hybrid

  
• Bus topology consists of a single line connecting all devices with terminators at each end, allowing other computers to read the data being sent from one to another computer
• Star topology includes a central server (‘Switch’) and all other computers connected with a dedicated connection to each, preventing collisions and enabling the server to send packets to different devices simultaneously and bi-directionally
• Mesh network setup involves every device directly interconnected to each other, commonly used for wireless networks like the Internet through the mesh connection of routers
• Hybrid topology is a combination of two or more topologies, like connecting LANs of different topologies
• Wired Networks use cables like copper (twisted-pair cable or coaxial cable) or fiber-optic cables connected to an Ethernet port on the network router

  
• Copper cables are less expensive and easier to install but are affected by electromagnetism and don't perform well with small charges
• Fiber-Optic Cables offer greater bandwidth, improved security, and are lightweight, but they need expensive optical transmitters and receivers
• Wireless Networks use radio waves, microwaves, or satellites to connect devices without cables, each having its benefits and drawbacks
• Radio waves can travel over large distances and are relatively inexpensive but transmit less data at one time and are affected by radio stations with similar frequency
• Microwaves have a larger bandwidth, can transfer more data at a time, but emitting towers are expensive to build and physical obstacles can interfere
• Satellites are cheap for long-distance communication, used for Satellite phones and radio broadcast, but are easy to interfere with and have an expensive setup
• Ethernet is the most common wired medium of transmission, used to transfer data between LANs or WANs, with the possibility of data corruption by signal collisions
• Bit Streaming is a sequence of digital signals transferred over a communication path at high speeds, requiring a fast broadband connection and some form of buffers for continuous data flow
• Two methods of bit streaming are Real-time and On-demand, each serving different purposes in broadcasting and online video viewing
• High broadband speed/bit-rate is crucial for downloading and displaying media simultaneously, especially for higher quality content and real-time streaming
• Cloud Computing provides on-demand computing services through the internet, offering infrastructure, platform, and software resources, with options like Public and Private clouds
• Public clouds are third-party services accessible via a browser, while Private clouds are owned by one organization and not shared with others
• Cloud computing requires less technical knowledge, is flexible for scaling, but may have poor data privacy and access issues during bandwidth problems
• The World Wide Web (WWW) is a collection of web pages stored on websites, transmitted using protocols across the Internet, a massive network of networks using TCP/IP protocol
• Internet is an interconnected network using IP addresses to identify devices, accessed through Internet Service Providers, supporting wired, radio, and satellite communication
• Routers connect networks, allowing internal connections between LANs or external connections from LANs to WANs, acting as gateways and firewalls
• LAN-supporting hardware includes Switches, Servers, Network Interface Cards (NIC), Wireless NICs, Wireless Access Points (WAP), and Cables for communication
• Bridge connects two LANs using the same protocol, storing network addresses for devices between the networks and ensuring message delivery
• Repeater regenerates data signals over the network to prevent signal weakening and corruption, ensuring data integrity during transmission
• Internet-supporting hardware like Modems allows devices to connect to the Internet via telephone lines, converting digital signals to analog for transmission
• PSTN refers to all telephone networks, providing dedicated lines for bi-directional communication between endpoints, even during power outages
• Cell phone networks are wireless networks divided into cells served by base stations, using radio waves for transmission and communication