How to insert these unicode symbols u2400 to u2421?

Question

Please how can I insert these unicode symbols in the range u2400 to u2421. They are names of control characters.

You can see them here: http://unicode.org/charts/PDF/U2400.pdf

I could find the package keystroke which has very nice keys, but that is not what I want.

Thanks!

-- Edited:

Quoting Marco: "The problem is to find a font that contains these characters."

Answer 1

It mostly depends on your setup. If you're using XeLaTeX or LuaLaTeX and fontspec it all boils down to

\newfontfamily{\lowasciifont}{Free Sans}
\newcommand{\lowascii}[1]{{\lowasciifont\char\string"#1}}

in the preamble and \lowascii{2400} and so on in the document. Example:

\documentclass{article}
\usepackage{fontspec}
\newfontfamily{\lowasciifont}{Free Sans}
\newcommand{\lowascii}[1]{{\lowasciifont\char\string"#1}}

\begin{document}
\lowascii{2400} \lowascii{2401}
\end{document}

Without XeLaTeX or LuaLaTeX I don't know of any font that has those symbols. One might conceive to create suitable Type1 fonts from FreeSans, but it's quite a job and probably its easier to fake those symbols with some low level trick.

Here's an example:

\usepackage{lmodern}
\newcommand{\lowascii}[1]{\innerlowascii#1\relax}
\def\innerlowascii#1#2#3\relax{%
  $\vcenter{
  \fontsize{4}{4}\sffamily
  \offinterlineskip
  \kern-1.2ex
  \sbox0{#1}\dimen0=\wd0 \box0
  \sbox0{#2}\moveright\dimen0\copy0 \advance\dimen0\wd0
  \if\relax\detokenize{#3}\relax\else\moveright\dimen0\hbox{#3}\fi}$}

In the text you can say

A \lowascii{NUL} \lowascii{LF} B

and get

Answer 2

The problem here is not how to enter the characters. You enter them as you enter all other characters, which depends on your keyboard layout and editor configuration. Either you enter them directly, you create a mapping for often used ones or you enter the unicode values directly. E.g. in vim you can do this with <CTRL-V>u<unicode_number>.

The problem is to find a font that contains these characters.