ALL TOPICS IN BULK - Incomplete

• CPU (Central Processing Unit):

  • Carries out program instructions using data
  • Components inside the CPU include ALU (Arithmetic Logic Unit) and Control Unit
  • Cache is a small, fast memory that holds frequently accessed items
  • Registers are ultra small and ultra fast, storing specific data
  • Special purpose registers include Memory Address Register, Memory Data Register, Program Counter, and Accumulator
  • Von Neumann architecture is built on these components
• Fetch Execute Cycle:

  • Fetch: Get instruction from memory using program counter address
  • Decode: Control unit interprets the instruction
  • Execute: Carry out the instruction, usually done by ALU
  • Data is fetched during execute
  • Results may be written back to memory at the end of the cycle
• Clock Speed and Cores:

  • Clock speed determines how often the fetch execute cycle is carried out
  • Clock speed is measured in gigahertz (billions of cycles per second)
  • Increasing clock speed makes the CPU work harder and do more cycles per second
  • Multiple cores allow for parallel processing, executing instructions simultaneously
• Cache Size:

  • Bigger cache stores more regularly used items, reducing reliance on slower RAM
  • Increases performance when cache size is increased
• Embedded Systems:

  • Computers inside other devices like household appliances and cars
  • Simple and have one specific purpose related to the device
• Storage Types:

  • Primary storage consists of RAM and ROM
  • Secondary storage is non-volatile and stores programs and data long term
  • Virtual memory is used when RAM is full, slowing down the computer
  • ROM contains the program that runs when the computer starts up
• Secondary Storage Types:

  • Magnetic storage (e.g., HDDs) uses magnetic polarity levels for binary representation
  • Optical storage (e.g., DVDs) uses light reflections for binary representation
  • Solid-state storage (e.g., SSDs) is fast, durable, and uses logic gates
• Binary Units:

  • Bit (0 or 1)
  • Nibble (4 bits)
  • Byte (8 bits)
  • Kilobyte (1000 bytes)
  • Each subsequent unit is a thousand times the previous one
• Binary, Hexadecimal, Decimal Conversion:

  • Binary, Hexadecimal, and Decimal have different place value tables
  • Conversion involves understanding the base values of each system
• Binary Addition and Shifts:

  • Binary addition follows the same rules as normal addition
  • Left shift doubles the number, right shift halves the number
  • Overflow error occurs when the result exceeds the storage capacity
• Character Sets:

  • ASCII and Unicode are character sets with binary codes for characters
  • ASCII has an 8-bit character code, while Unicode has room for thousands of characters
• Images:

  • Represented as pixels, with resolution indicating the number of pixels
  • Color depth is the number of bits per pixel, not the number of colors
• Sound:

  • Analog sound is converted to digital sound through sampling
  • Sample rate is the number of samples per second
  • Bit depth is the number of bits allocated to each sample
• Compression:

  • Reduces file size, lossy compression deletes part of the file
  • Lossless compression rearranges the file to be more efficient
• Network Types:

  • LAN (Local Area Network) and WAN (Wide Area Network)
  • Client-server network has central control, peer-to-peer network does not
• Network Topologies:

  • Star topology has a central node, easy to add new devices
  • Mesh topology has connections to every other device, high performing but complex
• Network Hardware:

  • WAP (Wireless Access Point) provides a wireless signal
  • Router forwards packets between networks
  • NIC (Network Interface Card) enables device connection to the network
  • MAC address is a unique worldwide address specific to hardware
• Transmission medium: NICs have built-in MAC addresses which are unique worldwide and pinpoint the correct device on a network
• Switches use MAC addresses within a single network to ensure packets go to the correct destination
• Data is split into packets when sent over networks, with IP addresses included in packet headers for routing
• Domain Name System (DNS) translates URLs into IP addresses for website access
• The cloud hosts resources and files accessible through the internet, offering high capacity and flexibility
• Protocols are sets of rules enabling device communication, organized in layers for flexibility
• CCP splits data into packets and handles errors like collisions
• Email protocols POP and IMAP handle email reception from mail servers
• Wired networks, like Ethernet, are more reliable with less interference and better security compared to wireless networks
• Cybersecurity attacks: SQL injection, brute force, denial of service, social engineering, and malware
• Prevention techniques: penetration testing, firewalls, physical security, anti-malware, user access levels, and encryption
• Operating system manages hardware and other programs.
• Utility software supports the general running of a computer system, including encryption, data compression, and defragmentation
• Legal aspects: Data Protection Act, Computer Misuse Act, Copyright Designs and Patents Act, open source vs. proprietary software, privacy issues
• Ethical issues: censorship, mass unemployment, surveillance, cultural and environmental impacts
• Magnetic storage?

  ~ A type of secondary storage which uses different levels of magnetic polarity

  EG: HDD

  ADVANTAGES:

  ~reliable

  ~large capacity, more data can be stored

  DISADVANTAGE:

  ~not durable because of its moving parts

  ~noisy
• Optical storage?

  ~A type of secondary storage which uses different reflections of light

  EG: a DVD

  ADVANTAGES:

  ~Portable and reliable as its small and compact

  DISADVANTAGES:

  ~Not durable as it can be easily scratched

  ~Low capacity per disk
• Solid state?

  ~A type of secondary storage which uses electronic circuitry

  EG: SSD

  ADVANTAGE:

  ~Have fast read and write speeds

  ~Durable

  DISADVANTAGE:

  ~Expensive
• Binary addition:

  • 1+1 = 0 carry 1
  • 1+1+1 = 1 carry 1
  • 1+0 = 1
• What does a binary left shift do?

  Shifts the bits of a binary number to the left, multiplying the number by 2.
• What does a binary right shift do?

  Shifts the bits of a binary number to the right, filling the leftmost positions with zeros and dividing by 2.
• What is an overflow error?

  Occurs when the result takes up more storage space than is possible
• Character set?

  ~A group of character codes

  EG: ASCII, Unicode

  
  

  ASCII = 8 bits per character, holds up to 256 characters

  DISADVANTAGE: not enough characters for other languages except English

  Unicode = can represent thousands of characters