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Introduction to Number system:
1. A Unit is something that denotes a single thing. Such as: A day, a meter etc.
2. A number denotes how many times a unit is taken. Ex: Rohit has Four pens.
3. A numeral is a symbol representing a number.
4. Numeration is expression in words of a number written in figure.
5. Place value: When a number consists of more than one digits each digit of the number has a value according to its position in the number. 
6. Face value: each digit in a number has a fixed value regardless of its position in the number.
7. Real numbers: Whole nos, Integers,decimal nos., Rational nos, irrational nos, etc.,
8. Binary digits also comprises of the number system.