Assign Roles Make sure everyone in your group has a new role. If you have 3 people, combine Facilitator & Process Analyst. Team Roles Facilitator​: reads the questions aloud, keeps track of time and makes sure everyone contributes appropriately. Spokesperson​: talks to the instructor and other teams. Compiles and runs programs when applicable. Quality Control​: records all answers & questions, and provides team reflection to team & instructor. Process Analyst​: Considers how the team could work and learn more effectively. Team Member Notes Facilitator: ● Note the start time, end time, and total amount of time it takes to complete each model ● Context: ● Model 1: ● Model 2: Context ­ Storage How many music files could you fit on your computer? That depends on how much space is available on your computer, and how your music files are compressed. On a Mac, click on the Apple in the top left corner, and then select “About This Mac”. Click on Storage to see the total size and available free space on your computer. On a PC, click on the Start button, and then click Computer. Click on the hard drive you want to check. The total size and available free space appear in the Details pane at the bottom of the folder window. A. Each person in your group should list the total size of your computer’s hard drive or flash storage. B. Each person in your group should list the available free space on your computer’s hard drive or flash storage. Model 1. (15 min) Bits and Bytes The following diagram and table explain how digital data is measured using bits and bytes. Fill in the table by calculating the powers of 2’s. bytes as power of 2 number of bytes kilobyte (KB) 210​
​ bytes megabyte (MB) 220​
​ bytes gigabyte (GB) 230​
​ bytes terabyte (TB) 240​
​ bytes Critical Thinking Questions 1.
How many bits are in a byte? 2.
A bit can either be considered on or off, or it can be considered a 0 or 1. a. Which number (0 or 1) corresponds to ON? b.
Which number corresponds to OFF? 3.
How many ​bits are there in a piece of data that is 10 ​bytes? Show your work. 4.
Consider the larger amounts of bytes. a. What is 210​
​ ? Fill in the rest of the table in Model 1 if you have not yet done so. b.
Why do you think a kilobyte is named a ​kilobyte, even though it is ​not 1000 bytes? c.
Is a 1,000,000 bytes closest to a kilobyte, megabyte, gigabyte, or a terabyte? d.
How many gigabytes are there in a terabyte? 5.
Go to this webpage​. a. Find the approximate number of MP3 audio files can be stored in 1 GB. b. Each member in your group should calculate the approximate number of MP3 audio files that can fit on your computer’s free space. c. List some types of files that require more space than audio files (on average). 6.
Download these two files: ● A plain text file containing just the words ​“I love computer science” ● A plain text file containing the text of Shakespeare’s ​Hamlet You can locate the exact number of bytes used to store a file on your computer. ● PC/WINDOWS: right­click and go to “Properties” ● MAC: Ctrl+click and go to “Get Info” Record the sizes here. File Name Size of the original file csLove.txt pg1524.txt 7.
Compress the files using the zip utility on the computer (right­click on the filename and send to zip or archive). Check the size of the zip file that results. Also calculate the compression ratio (the size of the zipped file divided by the size of the original file). Zipped File Name Size of the zipped file Compression ratio 8.
Did the larger file or the smaller file compress better? Model 2. (20 min) Text Compression An ​algorithm is sequence of instructions that solve a given problem. Compression algorithms allow us to decrease the number of bits needed to represent a piece of information. Text compression works by creating a dictionary of commonly used phrases in the text file. You’ll need to log into your Code.org account to complete this model. Critical Thinking Questions 9.
Start at stage 2​, and have ​each member in your group try to compress a ​different text file. Record your compression ratios for each text you attempted. Copy and paste the dictionaries that allowed you to achieve the compression ratios. 10. In stage 3​, decipher and then copy and paste the reconstructed text here. 11. In ​stage 4​, a. What is the compression rate, or the compressed text size + dictionary size compared to the original text size? b. Is this a "good" compression rate? Why or why not? 12. Discuss how each member in your group was able to compress the text for stage 2 (question 10). Then describe in full sentences at least two different strategies that your group members used. a. Strategy 1: b.
Strategy 2: 13. For a piece of text, what is a "good" amount of compression? Is there a way to know when you've compressed it the most? Explain how you would know, or why you can't know. 14. A ​heuristic algorithm is a type of algorithm that provides a reasonable solution that is not guaranteed to be the optimal solution. a. What would it mean to have the optimal solution for text compression? b. Why might it make sense to have a heuristic algorithm for text compression? Group Reflection Process Analyst​: Describe how your group worked separately to compress text (in question 10) and then worked together to compare strategies in question 12. Did this process of working individually and then together help your group members learn the material better? If so, explain why. If not, explain how this process might have gone better.