Once a bill becomes a law it is sent to the Archivist of the United States for publication. Public and private laws are assigned sequential numbers for each Congress. For example, the first public law passed by the 108th Congress is Pub.L. 108-1.

Laws are first published as individual unbound pamphlets known as "slip laws." After each session of Congress, laws are compiled into bound volumes in chronological order, known as the United States Statutes at Large.

Finally, public laws are incorporated into the United States Code, a codification of the general and permanent laws of the United States, arranged by subject. A new edition of the U.S. Code is issued every six years.

(Source: How Our Laws are Made)