orthography - When to spell out non-alphanumeric characters?

If a term contains non-alphanumeric characters, when (if ever) should these characters be spelled out? For example:

C++   written as   C Plus Plus

C#      written as   C-Sharp

If they are spelled out, what are the conventions regarding capitalization and hyphens (e.g. C Plus Plus or C-plus-plus)?

Answer

I hope I'm not stepping out of line, but since the comments contained several good answers, I thought it worthwhile to group them together into a properly credited answer. Currently it seems the community has found four reasons to spell out non-alphanumeric characters:

1. FumbleFingers noted that programming code can require spelling out such symbols to avoid creating problems during the parsing phase of a compiler/interpreter.


2. Waggers added that spelling out symbols can clarify pronunciation (e.g. "C#" as "C-sharp" rather than "C-hash" or "C-pound")


3. Hugo mentioned the concept of avoiding reserved characters in a tagging/keyword/categorization system.


4. Jay added that explaining the origin and meaning of such a term could require spelling it out. I think there's a lot of overlap between this and Waggers' answer about pronunciation.