In particular, the programs you write must obey a set of syntactic rules that define what commands and language forms are legal. When you program Karel to perform a task, you must write out the necessary commands in a very precise way so that the robot can correctly interpret what you have told it to do. Initially, Karel understands only a very small number of predefined commands, but an important part of the programming process is teaching Karel new commands that extend its capabilities. The process of specifying those commands is called programming.

By giving Karel a set of commands, you can direct it to perform certain tasks within its world. Karel is a very simple robot living in a very simple world. Hopefully this will get people thinking more about this powerful object-oriented, functional programming language.

And though it is so popular, most people dismiss it as a weak scripting language, and few people know it intimately. For the last three quarters, the hole in the curriculum left by Karel’s departure has been competently filled by Nick Parlante’s Binky world, but it seems about time to bring Karel back. But then, a year ago (2004), CS106A switched to Java, and Karel again vanished from the scene. We were, however, soon able to get a version of Karel up and running in the Thetis interpreter we were using at the time. In the middle of the 1990s, the simulator we had been using for Karel the Robot stopped working. Many generations of CS106A students learned how programming works by putting Karel through its paces. Karel was used in introductory computer science courses all across the country, to the point that Rich’s textbook sold well over 100,000 copies. (Rossum’ s Universal Robots) gave the word robot to the English language. That robot was named Karel, after the Czech playwright Karel Capek, whose 1923 play R.U.R. Drawing inspiration from the success of Seymour Papert’s LOGO project at MIT, Rich designed an introductory programming environment in which students teach a robot to solve simple problems. In the 1970s, a Stanford graduate student named Rich Pattis decided that it would be easier to teach the fundamentals of programming if students could somehow learn the basic ideas in a simple environment free from the complexities that characterize most programming languages.

Karel the robot program