The registered trademark symbol (®) is a symbol that provides notice that the preceding word or symbol is a trademark or service mark that has been registered with a national trademark office. A trademark is a symbol, word, or words legally registered or established by use as representing a company or product.  In some countries it is against the law to use the registered trademark symbol for a mark that is not officially registered in any country.
Trademarks not officially registered can instead be marked with the trademark symbol ™, while unregistered service marks are marked with the service mark symbol ℠. The proper manner to display these symbols is immediately following the mark, and is commonly in superscript style but is not legally required.
The registered trademark character has a standardized representation in most computer systems. It is mapped in Unicode as U+00AE®registered sign (HTML ®·®). The registered trademark symbol ® is distinct, in computer representation, from the similar character U+24C7Ⓡcircled latin capital letter r (enclosed R)
Because the ® symbol has not commonly been available on typewriters and ASCII-based computer systems, it has been common to approximate this symbol with the characters (R) (or (r)); for example, the Python programming language Trademark Usage Policy advocates this usage. However, these forms do not have legal force. Example of legal equivalents are the phrase Registered, U.S. Patent and Trademark Office, which may be abbreviated to Reg U.S. Pat & TM Off., in the U.S., and the letters RTM in the UK.
^PSF Trademark Usage Policy. https://www.python.org/psf/trademarks/ "The first or most prominent mention of a Python trademark should be immediately followed by a symbol for registered trademark: "®" or "(r)"."