Binary is the simplest numbering system, as digits are limited to only two possible symbols, (0 & 1).

A binary digit is given a special name, it is called a **bit**.

Quantities greater than one, are written using two or more bits.

- 1.
- 10.
- 100.

Like decimal the bits have different weightings, but in binary the weightings increase by a factor of 2, moving from right to left.

The symbol 1, in each of the above example represents:

- One in example i).
- Two in example ii).
- Four in example iii).

e.g.

- in example i) the right hand digit value is, 1 x 2
^{0}= 1 x 1 = 1. - in example ii) the middle digit value is, 1 x 2
^{1}= 1 x 2 = 2. - in example iii) the left hand digit value is, 1 x 2
^{2}= 1 x 4 = 4.

The left hand bit in a binary number has the greatest weighting and is called the most significant bit (**m.s.b.**).
The right hand bit in a binary number has the lowest weighting and is called the least significant bit (**l.s.b.**).