Tern is a tangible computer language designed to provide a painless introduction to computer programming for children in educational settings. With Tern you can create programs for robots like the LEGO Mindstorms RCX or the iRobot Create. Tern is featured in a permanent exhibit at the Boston Museum of Science called Robot Park. It is also being used for the Tangible Kindergarten project at the Tufts University Developmental Technologies group.

Programming with Wooden Blocks

To create programs with Tern, you don't use a mouse or keyboard. Instead, Tern allows you to create physical computer programs using interlocking wooden blocks that represent actions for your robot to perform. With Tern there is no such thing as a syntax error. The shape of the interlocking blocks creates physical syntax that prevents the creation of invalid programs. Tern programs can be compiled in a matter of seconds with the press of a button.

How It Works

Tern's wooden blocks contain no embedded electronics or power supplies. Instead Tern uses a standard webcam connected to a desktop or laptop computer to take a picture of your program, which it then converts into digital code using the TopCodes computer vision library.


Tern was created by Michael Horn at the Tufts University. It is currently being developed as part of an NSF-funded collaboration between the Tufts Developmental Technologies Research Group and the Tufts Human Computer Interaction Lab. Tern's team members include:



This video shows Tern in use at the Boston Museum of Science.


  • Bers, M. U., & Horn, M. S. (in press). Tangible programming in early childhood: Revisiting developmental assumptions through new technologies. In I. R. Berson & M. J. Berson (Eds.), High-tech tots: Childhood in a digital world. Greenwich, CT: Information Age Publishing.

  • Horn, M.S., Solovey, E.T., Crouser, R.J., and Jacob, R.J.K., Comparing Tangible and Graphical Programming Interfaces for use in Informal Science Education. In Proc. ACM Conference on Human Factors in Computing Systems CHI'09, ACM Press (2009).

  • Horn, M.S., Solovey, E.T., and Jacob, R.J.K., Tangible Programming for Informal Science Learning: Making TUIs Work for Museums. Proceedings of 7th International Conference on Interaction Design & Children IDC'08, (2008).

  • Horn, M.S. and Jacob, R.J.K. Tangible Programming in the Classroom with Tern. Proceedings of CHI'07 ACM Human Factors in Computing Systems (CHI Trends Interactivity), ACM Press (2007).

  • Horn, M.S., and Jacob, R.J.K., Designing Tangible Programming Languages for Classroom Use. Proceedings of TEI'07 First International Conference on Tangible and Embedded Interaction, (2007).

Download & Contact Info

We will post open source software and fabrication templates here soon. In the meantime, please email michael.horn [at] tufts.edu for information.