This is a guide for students attempting error control coding (one of the three encoding subtopics) in digital technologies achievement standard 2.44 (AS91371)

This is an achieved level guide.

Remember that you only need to do one of the three encoding topics (compression, encryption, and error control coding) to the excellence level. If you are either not interested in getting more than achieved, or are doing either encryption or compression to the excellence level, then this is the right guide for you. If you were wanting to do error control coding up to the excellence level, then you should select the alternate excellence guide instead.

In order to fully cover the standard, you will also need to have done projects covering the topics of encryption and compression to at least the achieved level (with one of them to the excellence level if you are attempting to get more than achieved), and projects covering the topics of representing data using bits and human computer interaction, and include these in your report.

Encoding has the following bullet points in achievement standard 2.44 which this guide covers.

Achieved: “describing the concept of encoding information using compression coding, error control coding, and encryption; and typical uses of encoded information”

As with all externally assessed reports, you should base your explanations around personalised examples.

You should read and work through the interactives in the following sections of the CS Field Guide in order to prepare yourself for the assessed project.

Read all of these sections, as they give the necessary introduction of the topics

9.1 - What’s the Big Picture?

9.3 - Check digits on barcodes and other numbers

Start this section by writing an introduction to the topic of error control coding. Briefly explain what error control coding is, what it is used for, and what kinds of problems would exist if there was no such thing as error control coding. Briefly describe what a check digit is, and how it fits into the larger topic of error control coding. This introduction only needs to be a few sentences - you are just showing the marker that you understand the bigger picture of what error control coding is, and some of the typical uses of it.

Now you are going to show an example of error control coding in action to include in your report. Get the packaging for a food you like, ensuring it has a barcode on it. Take a photo of the barcode and include it in your report, with a small caption saying what the product is and that you are going to use it to investigate check digits.

Enter the barcode number into the interactive in the field guide, and take a screenshot of the interactive showing that the barcode number is valid. Change one digit of the barcode number in the interactive and show that the interactive now says it is invalid.

Briefly describe how the barcode number checker interactive was able to determine whether or not the barcode number was valid.

  • Put error control coding in its own section (your report should have suitable headings and subheadings for each topic to make it clear for the marker) and ensure that you briefly introduce the topic. It is important that your report clearly demonstrates that you know the difference between encryption, error control coding, and compression, and what their different purposes are.
  • Be sure to shrink down examples so they do not take up too much space. A barcode only needs to be big enough for the numbers to be readable; it does not need to take up half a page!
  • This project should not take up more than one 1 page in your report. If it is going beyond a page then you have probably either not shrunk down your barcodes as much as you could, or are doing more than you need to.