The short answer: You can't.
Longer answer: You can, but it won't hold up. For your program to continue working, the source still has to be there in some form or another. This different form of your code might (emphasis on "might") be harder for a determined person to read, but if they have enough time they can recover the source or at worst an obfuscated version of the source.
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<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
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Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
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have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
Want more info? How to link or
or How to display code and escape characters
are good places to start.