ABSTRACT
In this chapter, we shall acquaint ourselves with the real number system. We introduce the set of real numbers in an informal way. Once this is done, the most important property of the real number system, known as the least upper bound property, is introduced. We assume that you know the set N of natural numbers, the set Z of integers, and the set Q of rational numbers. You know that N ⊂ Z ⊂ Q. You also know the arithmetic operations, addition and multiplication of two natural numbers, integers, and rational numbers. You also know the order relation m < n between two integers, more generally between two rational numbers.
