Click here to purchase the entire book in PDF format. Whole Numbers and Integers Once upon a time you learned how to count. You were probably taught to count your fingers... 1, 2, 3, 4 and so on. Although no one told you so at the time, you were being taught a set of numbers called whole numbers. Sometime after that, you were probably taught that there's one number that gets tacked on before the ones you already knew - the number 0. A little later, sometime after you learned about money and the fact that we don't have enough, you were taught negative numbers... -1, -2, -3 and so on. These are the numbers that are less than 0. That collection of numbers is called integers - all ``countable'' numbers that are negative, zero and positive. So the collection is typically written ... -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5 ...