Is putting a copyright symbol on your own software illegal?

Not illegal at all.

The soft was copyrighted to you the moment you wrote it, and adding the (c) serves notice that you aware of your rights and willing to enforce them.

No, it's not illegal, and it has been optional under the laws of most countries for many years. Your works are AUTOMATICALLY copyrighted the moment you created them. You can put your copyright notice on, or leave it off, it doesn't affect your rights.

However, if you register your copyright you can obtain some valuable legal rights including the option of claiming "statutory damages" of up to $150,000 for each piece of software someone copies illegally, regardless of what "actual" harm it may have caused you.

Distinguish this rule from the registered trademark symbol (R) which can ONLY be used on a brand that has been registered at the federal level.

You are not required to publish or register you work to secure a copyright.

The moment your work is created in a fixed or recorded form establishes a copyright.

You can place a copyright notice on your work without registering it.

Copyright 2010 All rights reserved.

or

Unpublished: © 2010, John Smith

THe © (ALT+0169) is a symbol for copyright and not registration....

However registration is required if you are going to take legal action to protect your work. You have roughly five years to register your work so that It proves to the court that you are the originator and the facts in your certificate are valid. You can register anytime within the life of the copyright. Early registration provides benefits if legal action is required. Registration also provides protection from importing of an infringing work by notifying US customs of your work.

No. That symbol serves as a reminder. Anything you write is already copyrighted. Government registration isn't necessary, but helps in a lawsuit.

You certainly should put the (c) on the software if YOU wrote it and it isn't a copy of someone else's work. It doesn't have to be registered. All you have to be able to do is prove the date it was first produced. A disk copy with a "saved" date on it should work fine if you ever have to go to court to prove it is yours.

From what I've heard, you can put the symbol on anything you want, and decent people will then honor that. But if someone decides to get uppity and challenge it and you have no documentation to back it up, your claim is harder to uphold.

Only if you distribute it for a profit is it illegal.

You're making a false statement by putting the symbol on it and claiming it is copyrighted, even though the US government doesn't say so. That's called false advertising, and it's incredibly illegal.

no, you should be just fine. although...that doesn't really make it copywritten and anyone that actually would care to steal your work could easily check that out.

soooo it's not really worth putting one on in the first place, but you can legally

No, I do not think it is illegal. But I think that the copyright doe sn`t count, so it is pointless.

Yes