Austrian pupils successfully set a world largest sorting network – based on CS Unplugged

With a successful world record attempt in Vienna, digital processes were translated into the analogue world, marking the kick-off of project ADA.

It is very easy to understand basic elements of computer science such as algorithms or sorting networks if one takes into one´s hand one of the most influential collections of materials for teaching computational thinking without using digital technology – CS Unplugged. One of such activities is “Sorting network” combined with sorting algorithms which occur in numerous programs and apps – they efficiently bring elements of a list into a certain order.

On 19.9.2019, pupils from the International School Klosterneuburg and Sir Karl Popper School together with computer scientists from the Vienna Center for Logic and Algorithms (VCLA) of the Vienna University of Technology (TU Wien) set a new world record – the world’s largest human sorting network. The activity was the prelude to a project ADA which aims is bringing computer science closer to young people and to foster gender mainstreaming in this discipline.

Sorting algorithms are extremely important in information technology and appear in many programs and apps. Sorting networks are special forms of such algorithms that can also be implemented directly in hardware, for example on graphics processors,” explains Prof. Stefan Szeider, initiator of the campaign from the VCLA of TU Wien to Austrian Press Agency.

Comparison nodes of the network represented by 1225 tiles

If you want to “build” a human sorting network, for example to sort the numbers from 1 to 50 according to their size, 50 people each carry a board with one of these numbers and stand on an entrance node. Then they go to the nearest sorting node and compare their numbers. According to the instructions, the person with the lower number goes to the right, the person with the higher number to the left, to the next sorting node. After several such passes, the persons with their numbers – sorted from 1 to 50 – arrive at the exit node. With 50 entry nodes and over 1,000 comparison nodes, the sorting network in Vienna is the world’s largest human sorting network ever recorded.

Computational thinking

Project ADA wants to teach students how to think in order to cope with the digital challenges of the future. For some decades now – made public by the American computer scientist Jeanette Wing – it has been recognized that people who deal with computer science “develop a very specific way of thinking,” as Szeider explains for the Austrian daily newspaper Die Presse. “Wing has called computational thinking. It is a kind of thinking that is algorithmic and process-oriented, in which abstraction and efficiency play a special role.”

Hermann Morgenbesser, computer science teacher at the International School Klosterneuburg, Future Classroom Lab, EUN Schoolnet and Scientix ambassador for Austria, whose students participated in the world record attempt, welcomes this initiative from Prof. Szeider. “What I find particularly important is the approach of bringing the human part of the digitalization process closer to the pupils. The imagination is trained by working with analogue examples and thus remains in the memory for a long time – and then it is easier for me as a teacher to teach algorithmic processes“.

The organizer of the activity at the Sir Karl Popper School, Denise Hackner, teacher of computer science, also says: “As a computer science teacher, it is very important to me that the students experience computer science outside of school and without sitting in front of a computer. Training algorithmic thinking in motion encourages different kind of learning, in this activity was kinetic.”

Inspired by Ada Lovelace

The event is the prelude to the VCLA project “Algorithms Think Different” (ADA), which aims to promote a gender mainstreaming and creative approaches to foster computational thinking, with open access materials and free workshops.

-In the coming months, the internationally acclaimed “CS Unplugged” collection of teaching materials will be published entirely in German.

-In October 2019, the project organized two hackathons, one part of the DigiEduHack and another part of Europe Code Week. In this Hackathons for Good AI the pupils´ task was to code a chatbot in Scratch which is able to help the user to lower one´s CO2 footprint, proper recycling, or choose sustainable transport on one´s root to school. “The “Hackathon for a good AI” is a good opportunity for young people to playfully deal with the topics of the future, and to reflect on the power the digital technology has in tacking challenges for global development and security, such as climate change”, says Meral Akin-Hecke, who was Austria’s Digital Ambassador from 2013 to 2017 as part of the “Digital Champions” initiative of the then EU Commissioner for the Digital Agenda, Neelie Kroes. The task of the Digital Champions is to pave the way for as many Europeans as possible to access the Internet and to support them in dealing with digital media.

-Last but not least, the activity called “Diary of the Computer Scientist” will transform the image of computer science as a male domain. The girls are to be offered the possibility of getting to know female role models personally, in their schools across Austrian. The ADA project is named after the British mathematician Ada Lovelace (1815-1852), who was the first female programmer to write history purely through informatics.


The world largest sorting network was sponsored by the Vienna Chamber of Commerce, in addition to the project´s funding by the Vienna Business Agency, and the Austrian Federal Ministry for Transport, Innovation, and technology. The Project ADA is supported by Future Learning Lab Vienna, the Austrian Computer Association and EIS Education Studios of the Austrian Federal Ministry for Education.

Photo gallery



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