small cap i for 1

Question

In the documentation of biblatex and csquotes packages, number 1 is replaced by a small cap i in the main text. I tried to find how in the source files but could not target any relevant piece of code. It looks like one way would be to define a \DeclareTextCommand{\is}{T1}{\textsc{i}{}} and then use \is978 in the source but in the mentioned documents, 1 is directly redefined as the new character (looking like) \textsc{i}.

Answer 1

It is not a small caps i, it is an old-style number 1. One way to get this is by using XeLaTeX and setting the main font to use old style numbers.

Most fonts (in my limited experience) do not have an old-style numeral 1 that looks like what you want. I think that the font used in the biblatex package documentation that gives the character you want is called Charter.

Here is a MWE:

\documentclass[11pt]{standalone}
\usepackage{xltxtra, fontspec}
\setmainfont[Mapping=tex-text, Numbers={OldStyle}]{Charter} %this is where you select the font
\begin{document}

Old style: 0123456789\\

\end{document}