The “C” in the circle is notice to the world that the associated work is protected by copyright law. Although not required by the Copyright Act, it may be placed on any published work. Registration of the copyright with the U.S. Copyright Office is not a prerequisite for placing the copyright notice on a work.
The “P” in the circle serves the same function as ©, however, it is reserved for published sound recordings.
Use of the the trademark and service mark superscript symbols are not controlled by any federal law or regulation. Businesses typically use these symbols to indicate that they claim rights in the mark although the Patent and Trademark Office (“PTO”) has not issued a registration. Because these symbols are not governed by federal trademark law, a pending trademark application is not a prerequisite for using them. Most important to understand is that use of these symbols does not confer any federal trademark rights.
The “R” in the circle indicates that the trademark is registered with the PTO. Although not required, the ® symbol may not be used before a registration has actually issued. When used, it should only be used on goods and services that are subject to a federal trademark registration and should be placed, when possible, directly following the trademark in superscript or in a smaller size than the trademark itself. Parenthetical use of the symbol is also permissible, e.g., (R). One does not have to use the trademark symbol with every appearance of the mark; however, it is good practice to use it when it first appears and where the trademark is prominently displayed.
Trademark users should exercise care in using the trademark registration symbol. Courts may impose liability for fraud, particularly if the user intended to mislead or deceive consumers by knowingly placing the symbol following a mark it does not own or following a mark, which is expired, cancelled or abandoned.
— Adam G. Garson, Esq.