The history of the symbolic representation of a copyrighted work dates back to the 17th century. This can be identified in the Scottish Almanacs of 1670 (an annual publication listing the events of the upcoming year). However, in the 19th century, under the U.S Copyright Act of 1802, the acknowledgement of such an authorization for the copyrighted work was provided through a lengthy notice.
The symbols "©" was first introduced in the U.S by the Copyright Act of 1909 after a few detailed discussions and meetings with the artists, who were reluctant to use the word "copyright" on their works, which appeared to be quite lengthy. The symbol © made it easier to represent that the work was registered under copyright. Initially it applied only to pictorial, graphic and sculptural works. However, the 1954 amendment allowed the usage of the symbol to any work, published and copyrighted. The practice of using "(C)" instead of "©" was accepted and further approved by the U.S Copyright Office under the Copyright Act of 1976 since the © symbol was not available on a typewriter and ASCII-based computer systems for a long duration.
Is it compulsory to display the "©" symbol?
No, it is not compulsory to display the "©" symbol along with your work. The Berne Convention Implementation Act of 1989 has made the usage of this authorization optional. According to this Convention , the creation of the work itself establishes the copyright. However, till date "©" is used in websites, images and other works as a means to indicate that the content is protected under copyright law.