In short, yes. It often makes sense to both register your work with the US Copyright Office and get a Creative Commons License if you want an easy way to share your work.

Copyright is a bundle of exclusive rights that are automatically granted to a copyright owner (artist, musician, author, choreographer, programmer) once the work is “fixed in a tangible medium” — written, recorded in audio or visual form, stored in a computer memory system. These rights are:

1. Copy the work;

2. Distribute the work;

3. Display the work;

4. Modify or create derivative works of the work;

5. Perform the work; and

6. In the case of sound recordings, to perform the work publicly by means of a digital audio transmission.