Teaching semaphores using... semaphores

Abstract

The word "semaphore" describes both a structure used in computing to manage concurrency and a signal used by trains and naval vessels to transmit information and prevent collisions. In this paper, we present a series of activities which help students build intuition about concurrency by managing "railway semaphores" using an open source train simulation game.

The increasing importance of multi-core computers and computing clusters makes concurrency an especially important topic in both operating systems and systems programming courses. Students often struggle to understand semaphores and concurrency problems. One reason for this is that these subjects are often presented as abstract mathematical objects which are hard to visualize. Using simulation to make these ideas more concrete can improve understanding and increase engagement in the course.

References

1. Akimoto, N., de Cheng, J., An educational game for teaching and learning concurrency, Proceedings of the 1^st international conference on knowledge economy and development of science and technology, 34--39, 2003.
2. Bedy, M., Carr, S., Huang, X., Shene, C., A visualization system for multithreaded programming, SIGCSE Bulletin, 32, (1), 1--5, 2000.
3. Bi, Y., Beidler, J., A visual tool for teaching multithreading in Java, Journal of Computing Sciences in Colleges, 22, (6), 156--163, 2007.
4. Burns, A., Davies, G., Pascal-FC: A language for teaching concurrent programming, SIGPLAN Notices, 23, (1), 58--66, 1988.
5. Bynum, W. L., Camp. T., After you, Alfonse: a mutual exclusion toolkit, SIGCSE Bulletin, 28, (1), 170--174, 1996.
6. Christopher, W. A., Procter, S. J., Anderson, T. E., The Nachos instructional operating system, Proceedings of the USENIX Winter Conference, 481--490, 1993.
7. Donaldson, J. L., Teaching operating systems in a virtual machine environment, SIGCSE Bulletin, 19, (1), 206--211, 1987.
8. Higginbotham, C. W., Morelli, R., A system for teaching concurrent programming, Proceedings of the Twenty-Second SIGCSE Technical Symposium on Computer Science Education, 309--316, 1991.
9. Holland, D. A., Lim, A. T., Seltzer, M. I., A new instructional operating system, Proceedings of the 33^rd SIGCSE technical symposium on computer science education, 111--115, 2002.
10. Hoskey, A., Simple OS: A component-based operating system simulator in the spirit of the little man, Journal of Computing Sciences in Colleges, 117--124, 2013
11. Kolikant, Y. B., Ben-Ari, M., Pollack, S., The anthropology semaphores, Proceedings of the 5^th annual SIGCSE/SIGCUE ITiCSE conference on innovation and technology in computer science education, 21--24, 2000.
12. OpenTTD developers, OpenTTD Wiki, http://wiki.openttd.org, retrieved April 2014.
13. OpenTTD developers, OpenTTD Wiki, http://wiki.openttd.org/signals/, retrieved April 2014.
14. Pfaff, B., Romano, A., Back, G., The pintos instructional operating system kernel, Proceedings of the 40^th ACM technical symposium on computer science education, 453--457, 2009.
15. Reese, D., Using multiplayer games to teach interprocess communication mechanisms, SIGCSE Bulletin, 32, (4), 45--47, 2000.