 Counting from zero is a very common practice in many computer languages, but why? Read on as we explore the phenomenon and why it is so widespread.

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

## The Question

SuperUser reader DragonLord is curious about why most operating systems and programming languages count from zero. He writes:

Computers traditionally tally numerical values starting from zero. For example, arrays in C-based programming languages start from index zero.

What historical reasons exist for this, and what practical advantages does counting from zero have over counting from one?

Why indeed? As widespread as the practice is, surely there are practical reasons for its implementation.

SuperUser contributor Matteo offers the following insights:

Counting arrays from 0 simplifies the computation of the memory address of each element.

If an array is stored at a given position in memory (it’s called the address) the position of each element can be computed as

``````element(n) = address + n * size_of_the_element
``````

If you consider the first element the first, the computation becomes

``````element(n) = address + (n-1) * size_of_the_element
``````

Not a huge difference but it adds an unnecessary subtraction for each access.