Source code blocks are delimited by #+BEGIN_SRC lang and #+END_SRC. emacs evaluates the source block and uses the result in export. Source block parameters, :results and :exports are particularly useful in this context.

:results can have the following options specified.

collection is either value or output. The first option instructs org-mode to capture the return value of evaluation and use it in exporting. The second option causes any output written to STDOUT to be used as the value of the source block.

type is one of table, vector, list, scalar, verbatim or file. By default, result is handled as a table or scalar depending on the value. Results of type scalar or verbatim are not converted to tables. A result type of file points to the file where the result is stored and causes a file link to be inserted.

format is one of:

• raw results are inserted directly into the buffer
• org results are enclosed in a #+BEGIN_SRC org block
• html results are assumed to be HTML and enclosed in a #+BEGIN_SRC html block
• latex results assumed to be LaTeX and are enclosed in a BEGIN_LaTeX block
• code result are assumed to be parsable code and are enclosed in a code block
• pp result is converted to pretty-printed code and is enclosed in a code block.
• drawer result is wrapped in a RESULTS drawer

handling is one of

• silent results are not inserted into the buffer
• replace any existing value is replaced with value
• append result is appended to existing
• prepend reslult is prepended to existing

:exports can have one of the following values.

• code body of source block is inserted into the buffer
• results result of source block evaluation is inserted into the buffer
• both code and results are inserted into the buffer
• none neither code nor results are inserted into the buffer

Here is a Python source code block which exports code and results.

#+BEGIN_SRC python :results value :exports both
# A simple Python source block
return 42
#+END_SRC

# A simple Python source block
return 42

42

Here is another Python source block whose output is captured and only the results is exported.

#+BEGIN_SRC python :results output :exports results
print "Hello, world!"
return 42
#+END_SRC

A blog post begins with the following.

#+TITLE: Blogging with org-mode
#+tags: emacs org-mode blogging
#+options: toc:nil num:nil tex:t LaTeX:t

Here is a \LaTeX{} block to generate an image in the exported document. By default, the result type is latex and the output is wrapped in #:BEGIN_LaTeX...#:END_LaTeX block. Note that there are no temporary graphics files generated at all.

\let\earth\relax
\input{eltex1}
\begin{figure}
\begin{center}
\begin{picture}(40,60)(0,0)
\grid{10}{8}
\end{picture}
\end{center}
\end{figure}

For latex source code blocks, default value of :results is output and :exports is results.

In contrast, the following block creates a graphic file as specified by :file argument. :results is specified as output file raw which causes the output to be interpreted as a file link. Note the use of raw without which the file link will be wrapped into a latex block.

We need to have graphviz installed on the system. emacs should be able to find dot command. As usual, Windows is a pain but I have become comfortably numb :)

You might need to locate and copy ob-dot.el to a location where emacs will find it.