The call number is part of the catalog record and is also marked on the item or attached as a label. People can understand the call numbers, but automated systems use bar codes instead. So bar codes are also created as part of the process of preparing library materials to go on the shelf. Look at the example below. Technical services people prepare materials for users.
Public services connect users with library materials.
I.American Library Association. 025.32 is the DDC classification number. On the Catalog page, you looked up a few book records. At least one should be non-fiction. Look at the call numbers and locate the books.