KS3 Data and data representation
How does a computer store an image? What happens if we decrease the quality of an image file? Can we recreate the original image if we decrease its' quality? Are there ways to reduce the size of an audio file without losing the quality of the audio when it is played back?
Understanding data and how it is represented within the computer system can help students become better programmers and better able to understand the limitations of the data processing. Knowing that no matter how much an image is enhanced no extra details can be added, or that if an audio track is down sampled data is going to be lost are both fundamental to understanding.
Colour by Numbers - Image representation
A resource from CS Unplugged which looks at ways in which images can be represented by black and white pixels. It includes a number of activities to help students look at the way in which Run Length Encoding can be used to minimise the actual size of data which has to be transmitted by a fax machine (or stored on a disk). A discussion of the underlying ideas is included.
Count the Dots - Binary Numbers
An introduction to the binary number system, this activity from CS Unplugged explains the theories which underpin the use of base 2, as well as why and how computers use this as their fundamental building block. A series of activities are included to help consolidate students understanding of the binary system, and include discussion of how characters and other types of data can be encoded.
Computational thinking and algorithms
An unplugged activity to convert binary numbers into coordinates that enable students to recreate an image using values given in binary. The resource also includes a spreadsheet which can be used to make more complex images for use with students at a more advanced level. The presentation is more of a discussion of computational thinking and is not really relevant to this activity. Once students have completed the activity for themselves, they could be asked to create their own image in a similar way to the one they have recreated, and generate a coordinate list for their image in binary. The discussions listed in the activity sheet should also be useful to broaden students understanding of the use of binary as well as how it might be possible to speed up a computer system in similar situations.
You Can Say That Again! - Text Compression
Reducing the amount of space that information occupies in a computer memory can make it easier to store more data, this activity from CS Unplugged looks at how text can be compressed so that no information is lost, but the overall file size can be significantly reduced. A series of activities to consolidate these ideas are presented along with an in depth discussion of what is going on in terms of the underlying computer science.