You can use "\ooo" where "ooo" is 1 to 3 octal digits. In other words, "ooo" can be "1", "304", "12", "77"....but not "o12."

You can also use "\xhh", where "hh" is 1 or 2 hexadecimal digits...ie, "\x34" or "\x9f" or "\xb."

This is the complete ascii table:
http://www.cs.utk.edu/~pham/ascii_table.jpg [Broken]

Some of the characters have special escape codes defined, such as "\n" for newline, which has hex value "A" and octal value "012", therefore the following are all equivalent:

\n
\xa
\xA (pretty sure this is case insensitive)
\012
\12 (im pretty sure the leading zero can be dropped)