Why do some attributes start with '@' while others done't?

[Brian Schott via Digitalmars-d]

On Thursday, 21 January 2016 at 23:14:14 UTC, Dibyendu Majumdar 
wrote:
> I see. And which approach is considered better? Personally 
> don't see why the '@' prefix is necessary.
>
> Regards

Without the "@", the following valid code would break:

bool safe = !aIsDangerous && !bIsDangerous;

Every time a new keyword is added to the language some working 
code will become invalid.