How to code sample code

Examples of displaying sample code

When putting sample code on an HTML page, there are several ways to do it. There are pros and cons to each approach. That the method supports markup could be a pro or a con depending on whether you want to mark up your code, or show the markup itself. (eg. I want to show <b>bold</b> and not bold, or vice versa.)

Using CODE

Pros: supported
Cons: Spaces are not preserved. others cons, see the code


Here is some code. 

    Line break and  spacing  must   be coded. with <br />. < less than. & ampersand are escaped.

Anything that looks like a <tag> must be escaped.
Tags are rendered.

Using PRE

pros: line breaks and spaces are preserved
cons: see the first paragraph about showing markup.

Code using PRE needs escaped < > &
    line breaks and spacing are preserved. I can still escape </pre>
Pre still marks up tags

Using xmp

Pros: everything (except </xmp>) is copied verbatim with no escaping of anything.
cons: officially not supported, but de-facto completely supported.

with xmp, I can put anything including < & and >. Line breaks and spacing are preserved. <b>tags</b> are not rendered. & entities are not recognized. The only thing I cannot type or display is

</xmp>

Using textarea

Pros: line breaks and spaces are preserved. Entities may or may not be preserved.
cons: a normal refresh will not change the contents of the textarea box when the source is updated.

I can put text in a textarea.
Line breaks   and    spacing are preserved and tags are not rendered.
    entities such as &gt; are rendered > 
However, & without a valid entity is given alone.
for(open(file) && file > 0)
<b>boldface?</b> The only thing I cannot put into a
<textarea> is the </textarea>

Conclusion

Textarea is best for arbitrary code. Great if you want to show markup
pre is great for marking up code with styles such as bold and italics
code is pratcically useless for blocks, but works well for inline styling.
xmp is the best for arbitrary code, but should never be relied upon.