You can include literal examples that should not be subjected to markup. Such examples are typeset in monospace, so this is well suited for source code and similar examples.
#+BEGIN_EXAMPLE Some example from a text file. #+END_EXAMPLE
For simplicity when using small examples, you can also start the example lines with a colon followed by a space. There may also be additional whitespace before the colon:
Here is an example : Some example from a text file.
If the example is source code from a programming language, or any other text that can be marked up by Font Lock in Emacs, you can ask for the example to look like the fontified Emacs buffer.
#+BEGIN_SRC emacs-lisp (defun org-xor (a b) "Exclusive or." (if a (not b) b)) #+END_SRC
To edit the example in a special buffer supporting this language, use C-c ' to both enter and leave the editing buffer.