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