It is all very well to have the real number system as points on the real line, butit is hard to prove any interesting facts about the reals without any convenientnotation for them. We now remedy this by introducing the decimal notationfor reals and demonstrating a few of its basic properties.We are all familiar with the following decimal expressions: 1 2 = 0.50000 . . .1 9 = 0.11111 . . .1 7 = 0.142857142857 . . .