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
  • Explain the role that processing plays in computation.


  • Forum
  • Cut out the number cards from Number Cards
  • 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


Report a Bug

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?

Teaching Guide

Warm Up (10 min)

What's Processing

Prompt: In the last lesson we reflected on the different inputs and outputs on a computer. Based on what you already know about inputs and outputs, write your own definition of "processing".

Discussion Goal

Goal: Use this prompt to quickly contextualize the lesson within the Input-Storage-Processing-Output model students have been exploring. You should have a visual of the ISPO model up to reference for the conversation. Note that the defintion of processing presented in the teacher comment is quite vague. Students only need to understand that processing is whatever a computer does to turn inputs into outputs. This definition will be refined later in the lesson.

Discuss: Have students write responses in a journal, then share with a neighbor, and finally discuss as a whole class.


This is a really great list of ideas. Processing seems to be whatever a computer "does" in order to turn inputs into outputs. Today we're going to do a couple of activities that help us better understand what processing means a little more clearly.

Sorting Cards


So far we've explored what inputs and outputs mean in the context of a computer. Today we're going to look more closely at processing by doing a couple of unplugged activities.

Group: Place students into pairs.

Distribute: Give each pair about twenty cards randomly chosen from the set of one hundred. Each set should be mixed and placed between the two students. Ask students not to touch the cards until you say so.

Teaching Tip

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 goal 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

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 cards, walk around and observe the different strategies they are using. As groups finish, give them their times but allow all groups to finish.

Discussion Goal

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.

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.

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?

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. Today, we're going to look at how a computer might solve this same problem.

Activity (40 mins)

Sorting Cards like a Computer

Distribute: Distribute one activity guide to each student (or pair of students).


You're going to sort your cards again, but this time, you'll have to plan your processing ahead of time, just as you would if you were programming a computer. In order to make sure that you aren't changing your plan according to the cards, the person sorting will not be allowed to look at the cards at all.

Teaching Tip

You will likely need to model the rules of the activity. You might have two students come up and demonstrate the rules.

Go over the instructions as a group. The rules are as follows:

  • Two students face each other across a desk, with a set of four number 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.

Teaching Tip

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.

Circulate: Walk around the room and listen to the types of ideas students are discussing. Encourage students to practice and to make sure everyone understands what they’re supposed to do. 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 the preparation time is over, bring the class back together and have them switch cards, so that each pair has a new random set of numbers. When they are ready, allow them to start sorting 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 discuss the strategy in pairs, then run one more trial with the Pointer and Sorter switched.

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 next 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 more time, but with eight cards.

Circulate: As before, walk around the room and listen to how teams are approaching the problem. Once preparation is over, run the activity again, making sure each student has a chance to be the Sorter.

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)

Computer Processing

Discussion Goal

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.

Discussion Goal

In the warm up, students were able to sort the cards without a strategy. Their instructions for the main activity had to be very specific, 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.

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In this lesson you'll learn how processing is used by humans and computers to turn inputs into outputs.


  • Algorithm - A precise sequence of instructions for processes that can be executed by a computer