Lesson 6: Processing
In this lesson, students complete a series of unplugged activities that explore the way information is processed by a computer. To begin, students race to sort a deck of cards as a team. Groups will iteratively improve their sorting strategy and reflect on what types of approaches lead to the best results. Afterwards, students will attempt to solve a related but more restricted problem in which they are sorting a small row of cards, in a reflection of the constraints of computer sorting. The lesson concludes with a discussion about how the problem was solved differently with the added restrictions and how it was easier to compare the efficiency of approaches in this restricted context.
The purpose of this lesson is to reinforce students' understanding of computers as machines that manipulate information, and to expand their model of information processing from simple bit manipulation to more complex problems, in this case sorting a deck of cards. By moving from an unconstrained "human" approach to solving this problem to a constrained "computer" approach, the lesson demonstrates that humans and computers can solve the same problem, but must approach them in different ways. As students formalize and generalize their strategies, the lesson motivates the value of clear rules and processes that are independent of particular data sets. Students also see that there are multiple valid approaches to solving a given problem, and begin to form criteria for evaluating them.
Warm Up (10 min)
Activity (40 mins)
Wrap Up (5 min)
Students will be able to:
- Develop, articulate, and implement a method for processing information based on given constraints
- Evaluate the effectiveness of multiple methods for solving an information processing problem
- One deck of cards per group of 3 students
- One copy of the activity guide for each student
For the Teacher
For the Students
- Algorithm - A precise sequence of instructions for processes that can be executed by a computer
How easy was it for students to understand the rules of the "Sorting Cards Like a Computer" activity?
Are students able to articulate a clear plan for the "Sorting Cards Like a Computer" activity?
Warm Up (10 min)
Review Review the model of a computer as a machine that inputs, stores, processes, and outputs information.
Last class, when we processed color using our color filters, we looked closely at how the computer changes the ones and zeros that represent information. Normally, we don't think about ones and zeroes when we work with information on the computer, even though that's how the information is represented on the lowest level. Today, we're going to do some infomration processing on a much higher level, using a deck of cards.
Group: Place students in groups, ideally of 3 but the activity will work with 2's and 4's as well.
Distribute: One deck of cards to each group. Each deck should be shuffled and placed in the middle of the group. Ask students not to touch the cards until you say so.
You should expect this first run of the challenge to be a little chaotic and that’s partially the point. This first run of the challenge motivates the need for a good problem definition and preparation. Make sure to stifle side conversations and keep clarifying questions at this point to the minimum necessary to complete the challenge.
Announce the rules of the challenge:
- Absolutely no talking during the challenge
- The goals is to put the cards in order as quickly as possible
- When you are done, a team member should say "Done!" and the teacher will give the team a time
If a student questions what order the cards should be in, just say that any reasonable order is acceptable. Once the class understands the activity and is ready, prepare a stopwatch, and then announce the start of time.
Circulate: While students are sorting their decks walk around and observe the different strategies they are using in order to help facilitate the subsequent discussion. Most groups will need at least a couple of minutes. As groups finish, give them their times but allow all groups to finish.
You can have groups check their own decks after the fact to make sure they are sorted, or facilitate an exchange between groups to have them check each other.
This discussion serves as a point to review the problem solving process and the importance of each step. Students did not have an opportunity to define their problem or prepare to implement their solution. Students should see that there are multiple possible solutions for "ordering" the cards, and that the group needs to agree on both the definition of "in order" and the strategy for sorting the cards in order to be effective.
Discuss What made this problem difficult? What strategies did you use? Were you able to use the problem solving process? You'll have a chance to try this activity again after you reflect on your strategies.
Activity (40 mins)
Sorting Cards with a Plan
That was pretty exciting but it was also a little bit chaotic. We’re going to run that same challenge again, but this time I’m going to let you develop a strategy with your group first. You may now talk as much as you like for the next few minutes, and afterwards we’ll see whether you can do any better. Remember, once the challenge starts you won’t be able to talk so make sure you’re all clear on your strategy now.
You’ll need to decide how openly you’d like to share times for each sorting in this lesson. You can individually report times to teams, have them record their own times (e.g. using a clock in the room), or record them on the board. Timing lets students see whether their algorithms are getting more efficient and it can also just be fun. Competition can be motivating for some groups but you’ll need to judge whether it will become a distraction in your class. So long as students can track their own improvement this activity does not actually rely on knowing the efficiency of other groups.
Distribute: Distribute one activity guide to each student and introduce the challenge on the first page.
Circulate: Walk around the room and listen to the types of ideas students are discussing. Encourage students to practice if they have time and to make sure everyone understands what they’re supposed to do.
Once the preparation time is over, bring the class back together. Ask them to thoroughly shuffle their decks (this should be done silently), place them in the middle of the table, and wait. When they are ready, start the second round of the activity and begin timing.
Circulate to observe how students handle the challenge. As groups finish give them their time. Once all groups are done ask them to check their decks and fill out their activity guides with their reponses.
Share: Have groups share the approaches they are using. The aim here is to give students a chance to hear how others are approaching the problem. Some groups may subsequently choose to update their approach based on ideas from other teams when they run the challenge the third and final time.
Hopefully you all have some ideas from hearing what other teams are doing, or you may just have some new ones of your own. I’m going to give you a few more minutes to update your strategies, and then we’re going to run this challenge one last time.
Circulate: As before, walk around the room and listen to how teams are approaching the problem. Once preparation is over, run the activity sorting activity one final time.
Prompt: Ask students to discuss and write responses to the question on the activity guide (also included below)
- What are the input, output, storage, and processing in this activity?
- How is your approach to solving this problem different from how a computer might have to approach it?
Discussion Goal: Try to highlight the following points as you synthesize comments from the room.
- The input is the unsorted deck. The output is the sorted deck. The storage is the placement of the cards at any point in time, and the processing is the reordering of the cards.
- Students may say any number of things here. It’s better to take a “no wrong answers” approach unless students offer ideas that truly contradict things they’ve already seen in the class.
Discuss: Give students an opportunity to talk at their tables about the prompts. Once they are ready to share ask a couple of groups to share their responses to each question.
There are many ways your solutions might be different from how a computer would solve this problem. In general, however, the biggest difference is that computers need to be programmed with a plan without knowing the exact cards that they are going to get. We're going to try this activity again, this time trying out our plan without looking at the cards.
Sorting Cards Like a Computer
Group: Students should be placed in pairs for the next activity or at largest groups of 3.
Go over the instructions for this phase of the activity as a group. The rules are as follows:
- Two students face each other across a desk, with a set of eight cards between them.
- One student, the Sorter, may touch and move the cards, but may not look at them.
- The Sorter may only pick up two cards at a time, and show them to the other student.
- The other student, the Pointer, may only point to the card that is higher.
- There is no other communication between the two.
You will likely need to model the rules of the activity. You might have two students come up and demonstrate the rules.
Circulate: Move around the room answering questions and checking on how students are approaching the problem. Reinforce the idea that they should have a strategy that works for every arrangement of the cards, not just the ones that they have out currently.
Once groups have a working strategy, bring the class back together.
Pairs should run the activity twice, switching which member is the Sorter and which is the Pointer. Between the two trials, allow students to consult with other teams to improve their strategies.
At the end of each trial they should flip the cards over and determine whether they were successful in sorting the cards.
Wrap Up (5 min)
Human vs. Computer Processing
This first share out should be very open-ended. The goal is just to hear the different approaches and identify common elements. Follow-up questions can ask whether the approaches they saw were the same or different from their own.
Share: Ask a couple of groups to share the types of strategies they considered when trying to solve this problem with the new constraints.
In both activities today students needed to communicate very clear instructions to one another to sort a deck of cards. Their instructions for the second activity had to be much more formal, however, and take into account the limited capabilities of the Sorter and the Pointer.
Prompt: Either as a discussion or silent journal ask students to consider the following prompt, also found on their activity guides.
- How did your problem solving process need to change in order to solve the card sorting problems with the constraints placed on the sorter and pointer?
- Could you have used a different strategy and achieved the same result? What might make one strategy better than another?
Discuss: Have students share their experiences with this new problem.
We just solved the “card sorting” problem in two different ways, one more like a human, and one more like a computer. Unlike humans, who can improvise, computers need very strict rules to follow, and those rules have to work in lot of different circumstances. Even with a very simple problem such as sorting a deck of cards, we had to plan very carefully to find rules that would work, and we saw lots of different and creative approaches. The set of instructions and rules that we create to solve a particular problem is called an algorithm.
Being creative as a computer scientist usually means understanding the limits of the machine we’re using, and then creating an algorithm to get it to process the input we have into the output we want. As we continue the unit, we'll be looking at more complicated problems that will require us to be even more creative on how we process information.
- Unit 1 Lesson 7 Overview
- Student Overview
Problem Solving - Computers and Logic: Lesson 7 - Human vs. Computer Processing
In this lesson you'll explore the differences between how humans and computers complete a common data processing task, sorting a list of information.