17.10. REPRESENTING DATA USING BITS (BINARY NUMBERS) (2.44)

This is a guide for students attempting Representing Data using Bits in digital technologies achievement standard 1.44 (AS91074). You will need to cover **two**different types of data to meet the requirements of the standard (each assessment guide only covers one). In order to fully cover the standard, you will also need to have done one more project for representing data using bits and projects covering the topics of *Encoding*and *Human Computer Interaction*, and included these in your report. ## 17.10.1\. OVERVIEW The topic of representing data using bits has the following bullet points in achievement standard 1.44, which this guide covers. Note that there is no excellence criteria for this topic. This assessment guide only covers one of the two types of data required for achieved. **Achieved**: “describing ways in which different types of data can be represented using bits” **Merit**: “comparing and contrasting different ways in which different types of data can be represented using bits and discussing the implications” As with all externally assessed reports, you should base your explanations around personalised examples. ## 17.10.2\. READING FROM THE COMPUTER SCIENCE FIELD GUIDE 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 topic 5.1 - What’s the Big Picture? (General information about bits) 5.4 - Representing numbers with bits (Relevant to the achieved criteria) 5.8 - Computers representing numbers in practice (Relevant to the merit criteria) ## 17.10.3\. PROJECT ### 17.10.3.1\. WRITING YOUR REPORT **Achieved** For Achieved, you need to demonstrate that you know how to convert decimal numbers (convention notation with 10 digits) into binary numbers. You can use a tool to help you do this, although you need to be able to describe how the answer was derived. You should show the binary representation for at least three numbers. Some ideas of numbers you could use are: * Your street number * The day and month of your date of birth * Your age * The age(s) of your sibling(s) Some more challenging ones if you are keen: * Your year of birth (e.g. 2002) * The population of a city or country * The distance between some cities (e.g. airline flight distances) Briefly describe how a number is converted to binary. **Merit** The material about representing numbers in practice may be challenging, so don’t worry if you need to read over it a couple of times! Think of a few different examples for different sized integers (both signed and unsigned ones) of a piece of data that you could store in that sized integer. For example, the age of a person could be stored in an 8 bit unsigned integer (people can’t be a negative age!), and the number of students in your school could be stored in an 8 bit or 16 bit integer, depending on how big your school is. Try to include examples of signed and unsigned integers, and of at least two different integer sizes. This means you will need at least three examples. The field guide gives some other examples (e.g. programming languages and IP addresses) that are affected by the number of bits used to represent a number. What are the consequences of making a wrong decision about how many bits to use to represent a number? In practice, how much of an issue is each of the consequences? Relate your answer to your examples above. Optional extra: Give an example of a situation where a 32 bit integer would not be suitable. What do we do in practice to address this problem? ## 17.10.4\. HINTS FOR SUCCESS * Remember that this part of the standard only goes up to the merit level. While you need to do some evaluation for merit, you should be mindful that the other topics go up to the excellence level, so they should make up the bulk of your in-depth discussions. * Remember to do a second project on a different type of data for the merit level. * Be careful to use personalised examples (i.e. represent different numbers to your classmates). It may be a good idea to pick a larger number (e.g. in the millions) to minimise the chance of it being the same as others. ## 17.10.5\. RECOMMENDED NUMBER OF PAGES We recommend that this project does not take up more than 1 page. Examples should be small, and discussions should be short and to the point, keeping in mind that there is no excellence criteria for this topic.