The number system is extremely old and has been expressed in many ancient cultures for practical uses. Currently the most popular type of number system that is prevalent today is known as the Hindu Arabic numerals. The number system notation development is credited to two great mathematicians from ancient India, Aryabhat (5th century BC) and Brahmagupta (6th century BC). The simplest number system where even number is represented by marks is known as the unary numeral system. Here each and every natural number is represented by the number of corresponding marks, much like the tally marks that are still in use. This system is still used for teaching theories in computer science and can be used in practical use, but for smaller numbers only.
The ancient Egyptians and Romans modified this concept and laid down their own numerical system for various practical purposes. Many others like the Mayan system used the base 20 system. The place value system of numbers that has a base of ten uses 10 digits from 0 – 9 for making the positional numeral system work. This system makes it easier for working in arithmetic rather than other numeral systems. For the purpose of computer science, a modified k positional system is used, which is known as bijective numeration.