CAIE AS Level Computer Science Flashcards

1. Information Representation

1.1. Data Representation

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• Two fundamental characteristics:

  
  

  • Base: Number of different digits in the system.

  • Place value: Specific value of a digit based on its position.

  
  

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• Number systems:

  
  

  • Denary (Base 10)

  • Binary (Base 2): Uses bits (0 or 1), e.g., 65 in binary = 01000001.

  
  

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• Denary vs Binary prefixes:
  
  

  Denary Prefix	Factor Value	Binary Prefix	Factor Value
  kilo-(k)	$10^3$	kibi-(Ki)	$2^{10}$
  mega-(M)	$10^6$	mebi-(Mi)	$2^{20}$
  giga-(G)	$10^9$	gibi-(Gi)	$2^{30}$
  tera-(T)	$10^{12}$	tebi-(Ti)	$2^{40}$
  Character Encoding Standards

  • ASCII: Represents English alphabet characters, with 128 possible characters (7 bits).

  • Extended ASCII: Extends ASCII to include various Latin alphabets.

  • Unicode: Superset of ASCII capable of representing many global languages, supports 256 characters (8 bits).

  1.2. Multimedia - Graphics, Sound

  Bitmap Images

  • Definition: Images made by assigning colors to pixels using bit patterns.

  • Resolution: Number of pixels; higher resolution = sharper, detailed images.

  • Color Depth: Number of bits for color representation; $2^n$ colors for an n-bit image.

  • File Size Calculation:

  $ext{File Size} = ext{Number of Pixels} imes ext{Color Depth}$$$ ext{File Size} = ext{Number of Pixels} imes ext{Color Depth}$$

  Sound Representation

  • Analog vs. Digital:

    • Analog data: Continuous signals, while Digital data consists of discrete signals.

  • Conversion: Analog signals are converted to digital via sampling at regular intervals.

  • Sampling rate: Number of samples taken per unit time; impacts accuracy of sound representation.

  • Bit Rate: Number of bits to store one second of sound:
    $ext{Bit Rate} = ext{Sampling Resolution} imes ext{Sampling Rate}$$$ ext{Bit Rate} = ext{Sampling Resolution} imes ext{Sampling Rate}$$

  Vector Graphics

  • Definition: Made of objects defined mathematically; can be resized without quality loss.

  1.3. Compression

  Lossless Compression

  • Original data is perfectly reconstructed; e.g., .bmp, .png files.

  Lossy Compression

  • Data is irreversibly eliminated to reduce size (e.g., .mp3, .jpeg).

  2. Communication

  2.1. Networks

  LAN vs. WAN

  • LAN: Local, connects devices within a small area; typically fast with low congestion.

  • WAN: Connects devices over larger areas; typically slower with higher congestion.

  Networking Types

  • Client-server model: Dedicated server handles multiple clients.

  • Peer-to-Peer (P2P): Each connected device acts as a client and server.

  Network Topologies

  1. Bus: Single cable; all devices on the same line.

  2. Star: Central node (hub) with dedicated connections.

  3. Mesh: Each device connected to all others.

  Networking Devices

  • Router: Connects different networks, manages traffic.

  • Switch: Connects devices in a LAN, directs data packets.

  3. Hardware

  3.1. Computer Components

  • Input: Gathers data from users.

  • Output: Displays data for user understanding.

  • Storage: Refers to both primary (RAM) and secondary (HDD/SSD) storage.

  3.2. Logic Gates

  • AND, OR, NOT gates perform basic logical functions in computing.

  Processor Fundamentals

  4.1. Central Processing Unit (CPU)

  • Architecture: Follows Von Neumann model, where data and programs share memory.

  • Registers: Fast storage locations in CPU that hold data and instructions.

  4.2. Assembly Language

  • Low-level programming closely related to machine code.

  4.3. Bit Manipulation

  • Enables operations like shifting bits to multiply or divide numbers.