(1) is practical. It is specially compiled for the shelving use of the Library of Congress. From category arrangement to number allocation, the actual needs of this collection are considered everywhere.

② There are more than 200,000 detailed classifications, which is the largest classification in the world.

③ It is not only suitable for comprehensive libraries, but also suitable for corresponding professional libraries.

(4) reflect new disciplines and new themes in a timely manner. The Library of Congress of the United States has a special department to manage LC, revise the category list in time according to the change of collection, publish the supplement and revision of LC every quarter, and report the revision information of LC category number in time.

⑤ The major categories are compiled independently, the publication time and edition are not uniform, and there is no unified compilation style, general breakdown table and general index.

⑥ The sequential labeling system is basically adopted, and the category number is short, but the category number cannot express the hierarchical relationship between categories and has poor memory.

⑦ Apply for LC number to be loaded into printed cards and machine-readable catalogues issued by the Library of Congress of the United States, as well as book cataloging data published by the United States, Britain and other countries. In addition to the Library of Congress, LC is also adopted by many university libraries, professional libraries in the United States and libraries in some countries outside the United States.