The Free On-line Dictionary of Computing (30 December 2018):

copyright symbol

    "©" The internationally recognised
   symbol required to introduce a copyright notice, a letter C
   with a circle around it.  This can be encoded in ISO 8859-1
   as character code decimal 169, hexadecimal A9, in HTML as
   ©, © or ©.

   A "c" in parentheses: "(c)" is sometimes used in documents
   stored in a coded character set such as ASCII that does
   not include the C in a circle, but this has no legal meaning.

   (2009-01-06)