AQA GCSE (8525) SLR 13 – Data representation

This download provides you with a zip file which contains all the resources you will need to deliver this topic.

It includes:

  • Student Learning Record Workbook (for use by students)
  • Student Learning Record Answers (for use by teachers)
  • End of Topic test and answers
  • Lesson PowerPoint’s for every lesson
  • Any associated answers or references sheets for class activities

This topic covers:

  • 3.3.1 – 3.3.8 from the specification (8525)

3.3.1 Number bases

  • Understand the following number bases:
    decimal (base 10)
    binary (base 2)
    hexadecimal (base 16)
  • Understand that computers use binary to represent all data and instructions.
  • Explain why hexadecimal is often used in computer science.

3.3.2 Converting between number bases

  • Understand how binary can be used to represent whole numbers.
  • Understand how hexadecimal can be used to represent whole numbers.
  • Be able to convert in both directions between:
    binary and decimal
    binary and hexadecimal
    decimal and hexadecimal

3.3.3 Units of information

  • Know that:
    a bit is the fundamental unit of information
    a byte is a group of 8 bits.
  • Know that quantities of bytes can be described using prefixes.
  • Know the names, symbols and corresponding values for the decimal prefixes:
    kilo, 1 kB is 1,000 bytes
    mega, 1 MB is 1,000 kilobytes
    giga, 1 GB is 1,000 Megabytes
    tera, 1 TB is 1,000 Gigabytes
  • Be able to compare quantities of bytes using the prefixes above.

3.3.4 Binary arithmetic

  • Be able to add together up to three binary numbers.
  • Be able to apply a binary shift to a binary number.
  • Describe situations where binary shifts can be used.

3.3.5 Character encoding

  • Understand what a character set is and be able to describe the following character encoding methods:
    7-bit ASCII
  • Understand that character codes are commonly grouped and run in sequence within encoding tables.
  • Describe the purpose of Unicode and the advantages of Unicode over ASCII.
  • Know that Unicode uses the same codes as ASCII up to 127.

3.3.6 Representing images

  • Understand what a pixel is and be able to describe how pixels relate to an image and the way images are displayed.
  • Describe the following for bitmaps:
    image size
    colour depth
  • Know that the size of a bitmap image is measured in pixels (width x height).
  • Describe how a bitmap represents an image using pixels and colour depth.
  • Describe using examples how the number of pixels and colour depth can affect the file size of a bitmap image.
  • Calculate bitmap image file sizes based on the number of pixels and colour depth.
  • Convert binary data into a bitmap image.
  • Convert a bitmap image into binary data.

3.3.7 Representing sound

  • Understand that sound is analogue and that it must be converted to a digital form for storage and processing in a computer.
  • Understand that analogue signals are sampled to create the digital version of sound.
  • Describe the digital representation of sound in terms of:
    sampling rate
    sample resolution
  • Calculate sound file sizes based on the sampling rate and the sample resolution.

3.3.8 Data compression

  • Explain what data compression is.
  • Understand why data may be compressed and that there are different ways to compress data.
  • Explain how data can be compressed using Huffman coding.
  • Be able to interpret Huffman trees.
  • Be able to calculate the number of bits required to store a piece of data compressed using Huffman coding.
  • Be able to calculate the number of bits required to store a piece of uncompressed data in ASCII.
  • Explain how data can be compressed using run length encoding (RLE).
  • Represent data in RLE frequency/data pairs.

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