How can you identify Dewey decimal classification system?

The Dewey Decimal Classification (DDC) system is identified by its use of three-digit numbers to categorize books and materials in libraries. Each number corresponds to a specific subject area, with the system organized into ten main classes, such as 000 for general works and 900 for history. Within these classes, further subdivisions are indicated by additional digits, allowing for more precise categorization. You can often find the Dewey Decimal number on the spine label of library books.