Communications of the ACM

Broadening participation

Reaching a Broader Population of Students Through 'Unplugged' Activities

By Thomas J. Cortina
Communications of the ACM, March 2015, Vol. 58 No. 3, Pages 25-27
10.1145/2723671
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The first decade of this century saw growth in outreach to raise awareness of computing and the possibility of a career in computing. Some of these efforts were "unplugged," not requiring a computer, but providing an easy, fast way to present key principles of computer science to a broad audience. This column highlights Computer Science Unplugged (CS Unplugged; www.csunplugged.org), activities that are easy to present, require few materials, encourage collaborative work, and do not depend on hardware, compilers, browsers, and Internet connections. They work well when access to computers is limited or nonexistent.

CS Unplugged was developed at the University of Christchurch in New Zealand by Timothy Bell, Ian H. Witten, and Mike Fellows, and adapted for classroom use by Robyn Adams and Jane McKenzie.² Activities include basic concepts such as computer data storage, how computers compress information and detect errors, and algorithms for solving common computational problems (searching, sorting, finding minimal spanning trees, using finite automata to model systems). Kids do not simulate a computer (not a particularly interesting endeavor) but learn problem-solving skills that expose fundamental computer science concepts.¹ CS Unplugged activities promote group work, problem-solving skills, and creativity.

For example, a teacher can start with magnets or self-stick notes of two different shapes and ask a child to put a random set of these into a 7 × 7 grid as shown in the example here:

The teacher, or someone who is in on the "trick," can then claim to make the problem even more difficult by adding an eighth row and eighth column with seemingly random choices:

The teacher can then leave the room, and a child can change one of the magnets to the other magnet. For example, the child changes the magnet in the second row and third column from X to O:

The teacher returns and magically picks out the magnet that changed, astounding the children. The teacher asks how this is possible, giving children a chance to discuss solutions with each other, expressing various algorithms or techniques that may have been used. Often, students will eventually see the teacher did not put in a random eighth row and eighth column. Instead, the extra row and column set the number of each magnet in each row and column to be even. The change creates exactly one row and one column with an odd number of each magnet, leading to the magnet that was changed.

The computational thinking principle illustrated in this activity is that of parity, detecting errors in data, which computers have to do constantly. The CS Unplugged activity write-up gives teachers information about parity that they can present to children along with extension activities. For example, what happens if two magnets changed? Can we detect that the change occurred? Can we identify which magnets changed?

One of the keys to the success of CS Unplugged and its use worldwide is the fact the activities do not require a computer at all. Some schools do not have a computer lab for students to write code. If they do have computer labs, they are often used for word processing and Web surfing for research for other courses. CS Unplugged activities can be done entirely without computers. When the CS4HS (Computer Science for High Schools) workshop was launched at Carnegie Mellon University in 2006, participating high school teachers said they could not teach computer science because they did not have any computers, or enough computers, in their schools. The workshop started with CS Unplugged, and all of the teachers subsequently reported using these activities successfully in their schools the following year with an increase in student interest in computing.

Activities in CS Unplugged support the principle of computational thinking,⁵ which promotes the idea that problem-solving skills and computational techniques used in computer science should be a part of every person's education and are applicable to a wide variety of fields, not just computer science. Although one study suggests CS Unplugged activities do not inspire young people to pursue computer science in college,⁴ the primary goal of these activities is to expose students to computing as an intellectual discipline that goes beyond their understanding of computers as a tool and a toy. Additionally, these unplugged activities are meant to be supplementary, used for short periods to get kids working together, and to give teachers and students a chance to step away from the computer and programming-based activities. More formal studies are needed that validate that CS Unplugged is effective in meeting its goals.

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It is one thing for students to click the Compress option for a file. It is another thing to gain an appreciation for how that process works.

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Another key to the widespread use of CS Unplugged is its ability to get kids engaged in the activities physically, and most activities encourage group work so kids work together to solve problems, much like computer scientists do when working on large complex software and hardware systems. CS Unplugged exemplifies an educational theory known as experiential learning, where participants learn through activity outside of a standard academic setting.⁵ By being physically part of the solution to a problem as it is being solved, kids learn from observations and experiences. Unlike some introductory programming activities that tend to promote solo activity, the CS Unplugged activities put kids physically in the middle of the problem, getting them moving, working together, sharing ideas, and designing solutions.

One activity in CS Unplugged involves compressing text by finding repeated letter sequences. Kids can work together to compress some large paragraphs to a fraction of their size, competing to see who can compress the text the most. As a result of this activity, kids learn one way their computer makes files smaller so they can store more on their hard drive. It is one thing for them to click the Compress option for a file. It is another thing to gain an appreciation for how that process works. And some kids wonder if there are other compression algorithms and why this one works so well, leading to further exploration.

Another activity simulates parallel sorting, where children walk through a parallel sorting network drawn on the ground with chalk, comparing themselves using some measure with other children they encounter, following the appropriate path to another node in the network until they reach the end. They see that no matter how they are organized initially, the network will lead them into sorted order. The activity comes with several networks the teacher can use, and it can be adapted based on the number of students in the activity.

Yet another activity involves a set of "islands," with children traveling from one island to another on "pirate ships." As a child arrives at an island, the island's overseer (a teacher or another child) gives them two options to travel from that island to another island: A or B. Depending on which letter the child picks, they are sent to one or another island to then answer the same question. Their goal is to find their way to Treasure Island, and as they move from "island" to "island," filling in a map with their choices, they are forming a finite state automata. Students will share information to find the fastest path to Treasure Island, the longest path (which involves cycles), all of the paths, and so on, describing them as a regular expression. Later, the teacher can show how they can look at this problem abstractly as a set of states with directed edges labeled "A" and "B," and how automata can be used to describe other complex systems like traffic lights and vending machines.

CS Unplugged activities are gender neutral and encourage participation by all groups. Illustrations in the activities show pictures of boys and girls performing the activities. The National Center for Women in Information Technology (NCWIT), has included CS Unplugged in its materials for teachers to encourage girls to learn about information technology and pursue a career in IT.^a Exploring Computer Science, a curriculum for secondary-level students that has been used successfully in school districts with significant minority populations like those in Los Angeles and Chicago, has included CS Unplugged in its unit on problem solving.^b Carnegie Mellon University uses CS Unplugged in its TechNights workshops to encourage middle school girls to learn about computer science,^c and Howard University has used CS Unplugged to increase awareness and appreciation of computational thinking for African American students.^d

CS Unplugged has also been used in events sponsored by AccessComputing^e at the University of Washington for young people with disabilities. For example, blind children with their canes sitting in a row of chairs represents an unsorted array. The children learn various comparison-based sorting algorithms by comparing the lengths of their canes and moving to the appropriate chairs depending on whose cane is longer. When sorting by birthdays they shout out their birthdays according to an algorithm. This allows a group of children to stand up together to move in unison to the next chair, thus demonstrating a parallel sorting algorithm. The concept of a parallel algorithm and broadcast become quite real to the children in the process of executing the algorithm in their chairs.

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With a little creativity, the activities in CS Unplugged can be adapted for any population.

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With a little creativity, the activities in CS Unplugged can be adapted for any population. In fact, the CS Unplugged website lists numerous extensions for each of the original activities, submitted by volunteers all around the world. The activities have had such an impact that the CS Unplugged curriculum, originally published in English, has been translated to a number of languages such as Spanish, German, French, Italian, Portuguese (Brazilian), Polish, Russian, Slovenian, and Japanese.

CS Unplugged is not the only unplugged way to introduce computing ideas to kids. Tinkersmith, an organization based in Oregon, has developed a number of activities for K–12 students that do not require computers including Binary Baubles and My Robot Friend. Binary Baubles involves using hands-on techniques to have kids encode text using ASCII, and other methods. My Robot Friend requires participants to write programs on paper for a "robot" (another participant) to follow to stack a set of cups into a particular configuration. Another organization, Kodable, has activities that teach kids how to program by having them program each other using a graphical set of instructions (for example, squat, jump, rotate, grab) to navigate obstacles and reach a goal. CS Unplugged is included, along with these unplugged activities, as part of the Hour of Code^f for schools that either do not have computers or that want to include other computing activities beyond computer programming.

Since it was first introduced in 1998, the growth in the use of CS Unplugged by organizations and teachers provides evidence that this method of introducing computing to kids is a valuable resource regardless of whether or not they have access to computers. As computing professionals, we should encourage the addition of unplugged activities in our schools to help children see the ingenuity, creativity and teamwork involved when working on computational problems. We should help to create, study, and evaluate new unplugged activities for teachers to use to reach a more diverse population of children. Through these efforts, we just might connect with young people who never thought computing could be a potential career path, and change their minds.

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