CAIE AS Level Computer Science Flashcards

1. Information Representation

1.1. Data Representation


  • Two fundamental characteristics:

  • Base: Number of different digits in the system.
  • Place value: Specific value of a digit based on its position.


  • Number systems:

    • Denary (Base 10)
    • Binary (Base 2): Uses bits (0 or 1), e.g., 65 in binary = 01000001.


  • Denary vs Binary prefixes:

    Denary PrefixFactor ValueBinary PrefixFactor 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:

    extFileSize=extNumberofPixelsimesextColorDepthext{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:
      extBitRate=extSamplingResolutionimesextSamplingRateext{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.