Additive number system

Additive number systems are number systems where the value of a number is the sum of the values of its digits. This system of notation is called the sign-value notation. Additive systems stand in contrast to positional number systems, where the value of digit changes based on its position in the number.

Usage
A pros of additive number systems is their simplicity, especially with strictly additive systems, relative to positonal systems. However, since humanity uses a positional number system (Decimal), this argument is largely moot nowadays.

In the past, additive number systems were often the norm, as the majority of number systems used by old cultures. Even the ones that used a positional number systems, like the Babylonians, additively encoded the digits.

Contrary to positional numeral systems, there is no easy way to define a parameter around which to construct an additive numeral system (like the positional radix), since the amount of digits can be any integer greater than 0.

Some strictly additive systems can fit into the positional notation framework. The main example of this is unary, which can also be defined as the bijective base-1 number system.