The bar code is lost, and the book can still be recognized! Barcodes are added to books when they are processed, so as to register their properties. This book has no unique bar code? When searching for books, you can search for old books by their titles. This includes barcode information, which means that there are several barcodes in a book with the same title. By querying the book circulation records, you can find the bar code of the book you borrowed. Even if you lose the barcode, there is still data stored in the library system.