Question

This excerpt is from "Copyright Notice," an article found in Circular 3, a publication of the United States Copyright Office. What is the meaning of the word "mandatory" in the sentence above

Answer 1

The meaning of the word mandatory here is, required.

The excerpt of the copyright notice clearly states that before a certain given date the use of copyright notice was required on all published works.

And if the work did not have the notice on it it would result in the copyright protection.