What does positional weighted system mean?

Layman:

  • Each position of a digit in a number carries a different weight.

Formal: ( an an-1 … a0 . f1 f2 … fm ) base10 = (an x 10^n ) + (an-1 x 10^n-1 ) + … + (a0 x 10^0 ) + (f1 x 10^-1 ) + (f2 x 10^-2 ) + … + (fm x 10^-m )

Example:

2915 (Base 10)

Each digit 2, 9, 1, 5 has a weight of 2 * pow(10, 3), 9 * pow(10, 2), 1 * pow(10, 1), 5 * pow(10, 0)