What happens when Karel encounters a command it does not understand?

When Karel encounters a command it does not understand, the appropriate response is for Karel to throw an error. This means that Karel has a strict interpretation of its command set and does not try to guess or continue with the program when it encounters an unfamiliar command. Throwing an error helps with debugging by clearly indicating that something has gone wrong; it also prevents Karel from executing potentially harmful or unintended actions due to a misinterpreted command.

In programming, it is crucial for a robot or program to behave predictably, so throwing an error is a way to maintain reliability and ensure that only valid commands are executed. This behavior aligns with good programming practices, where encountering an error can signal to the programmer that there needs to be a review or correction of the code being executed.