People who used the abacus began to notice the importance of the different values of the columns. For example, six beads in the hundreds column were ten times greater in value than six beads in the tens column. This led to one of the most important discoveries in the history of numbers: the place-value system of numeration.
In a place-value system, the numbers of units tens, hundreds, ... , are each represented by a single numeral. However, each numeral must be written in a special position or place. Thus, for any whole number, the units place is at the right-hand end of the number, the tens place is next to the units place on the left, and so on. For example, the number 3902 means 3 thousands 9 hundreds, 0 tens and 2 units