Every elementary school teacher will agree that the concept of zero is difficult for mimy children to grasp. In fact, many teachers themselves are uncomfortable when they must work with numbers involving zero. One veteran fifth-grade teacher was observed drilling her students to repeat that 6 × 0 = 0, but that 0 × 6 = 6. Apparently she didn't really believe the commutative law which she had previously “taught” her students. Moreover, the role of zero in the structure of the number system was at best vague and certainly confusing to her. We will never know how many hundreds of students she had confused about zero over the long years of her teaching career. The fault does not lie entirely with the teacher alone, of course. At least one textbook she had used in years past made quite a point of stating that zero is not a number. Such mjsinformation as this could only confuse both teacher and students. After all, she might reason, if zero is not a number, it is not obliged to follow the laws of numbers such as the commutative Jaw for multiplication.