Positional notation occurs when we assign a positional value to each digit in a real number, from right to left.

For the number 4782, for example, starting with 2, and counting from right to left, the positions are 0,1,2,3 as in the following:

4782 → number

3210 → positional values

Weighted coding:

In the above example, the positional assignments 0 through 3 can be weighted values of their assigned digits.

So, the wiehgt of 4 is 3 and the weight of 7 is 2.

The weight of a number comes into play while converting from any base numbering system to the decimal numbering system.

Some of the weighted codes are BCD codes, 2421.

Non-weighted codes:

Gray code is a non-weighted code method that alters just one bit in a binary number when moving from one decimal to the next.

In normal binary coding, the digits 10 would represent the decimal number 2.

Excess-3 is another non-weighted coding method. You add 3 to  a decimal number before converting it to binary.

So, the decimal number is 2, for example, would first increase by 3, making it to 5.

The binary conversion of 2 using excess-3 method would be 0101 instead of its normal binary value 0010.