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Memory and Storage - Coggle Diagram

- - - - Each character is represented by a binary value
      - Includes uppercase/lowercase letters, numbers and punctuation
      - A character set defines the characters a computer can represent
    - - American Standard Code for Information Interchange
      - Originally developed for the English alphabet
      - Uses 7 bits
      - Represents 128 characters
      - Includes letters, numbers, punctuation and spaces
    - - Uses 8 bits
      - Represents 256 characters
      - Includes additional characters such as © and ®
    - - Represents characters from different languages and emoji
      - 16-bit Unicode: 65,536 combinations (2 bytes)
      - 32-bit Unicode: over 4 billion combinations (4 bytes)
    - - ASCII character "7" is different from integer 7
      - Character "7" is stored using its character code
      - Integer 7 is stored as a numeric binary value
      - Characters cannot be used directly for arithmetic
      - In Python, convert string input using int()
    - - Joins strings together using +
      - Example: "Mike" + " " + "Bell" produces "Mike Bell"
  - - - Denary: base 10, digits 0-9
      - Binary: Base 2, digits 0-1
      - 8-bit column values: 128, 64, 32, 16, 8, 4, 2, 1
      - Binary to denary: add the column values where there is a 1
      - Denary to binary: use the column values to make the required total
    - - Base 16
      - Uses 0-9 and A-F
      - A = 10, B = 11, C = 12, D = 13, E = 14, F = 15
      - Used because it is shorter and easier to read/write than binary
      - Each hex digit represents 4 bits
    - - Hex to denary: multiply left digit by 16, then add right digit
      - Denary to hex: divide by 16; quotient is first digit, remainder is second
      - Binary to hex: split into two 4-bit nibbles and convert each
      - Hex to binary: convert each hex digit into 4 bits
    - - 0 + 0 = 0
      - 0 + 1 = 1
      - 1 + 0 = 1
      - 1 + 1 = 0, carry 1
      - 1 + 1 + 1 = 1, carry 1
    - - Occur when the result is too large for the available number of bits
      - Example: a result requiring 9 bits cannot fit into one 8-bit byte
    - - Left shift: moves bits left; fills empty spaces with 0
      - Right shift: moves bits right; fills empty spaces with 0
      - Left shift one place = multiply by 2
      - Right shift one place = divide by 2, rounding down
      - Shifting can lose accuracy if 1s are removed
  - - - Bitmap/raster: made up of pixels
      - Vector: uses shapes/paths rather than individual pixels
      - Formats: BMP, JPG, GIF, PNG, TIFF (bitmap); SVG (vector)
    - - Pixel = smallest identifiable area of an image
      - Each pixel represents one colour using binary
      - Resolution = number/concentration of pixels in an image
      - Expressed as width × height, e.g. 1920 × 1080
      - Higher resolution = larger file size
    - - Number of bits used to represent each pixel
      - More bits = more possible colours
      - 1 bit = 2 colours
      - 2 bits = 4 colours
      - 8 bits = 256 colours
      - 16 bits = 65,536 colours
      - 24 bits = 16.7 million colours
      - Number of colours = 2ⁿ
    - - Colours made from red, green and blue
      - Each RGB value ranges from 0-255
      - Each colour requires 8 bits
      - Total = 24 bits per pixel
      - 32-bit colour uses an extra 8 bits for transparency
    - - Data about the image, rather than the image itself
      - Includes colour depth, resolution, date created and author
      - Stores information needed to describe the image
    - - Higher resolution = more pixels = larger file
      - Higher colour depth = more bits per pixel = larger file
      - File size (bits) = width (pixels) × height (pixels) × bit depth (bits per pixel)
  - - - Analogue sound = continuous signal
      - Digital sound = discrete values
      - Sound is digitised by repeatedly measuring the sound wave
      - ADC: converts analogue input into digital signals
      - DAC: converts digital signals into outputs
    - - Sample = measurement of a sound wave's amplitude at a given time
      - Sample rate = number of samples per second
      - Measured in Hertz (Hz)
      - 1 Hz = 1 sample per second
      - CDs typically use 44,100 Hz (44.1 kHz)
    - - Number of bits used to record each sample
      - More bits = more accurate measurement of wave height
      - Higher bit depth = larger file size
    - - Higher sample rate = more samples per second
      - Greater accuracy and more detail
      - Higher sample rate = larger file size
    - - File size (bits) = sample rate (Hz) × bit depth (bits per sample) × duration (seconds)
      - Divide by 8 to convert bits into bytes
    - - MP3 removes sounds that are less noticeable
      - Lossless examples: FLAC, ALAC, WMA Lossless
      - WAV and AIFF are uncompressed
      - AAC is typically higher quality than P£