You can access any character of the current font using its number with
the \symbol command. For example, the visible space character
used in the \verb* command has the code decimal 32 in the
standard Computer Modern typewriter font, so it can be typed as
\symbol{32}.
You can also specify numbers in octal (base 8) by using a '
prefix, or hexadecimal (base 16) with a " prefix, so the
visible space at 32 decimal could also be written as
\symbol{'40} or \symbol{"20}.