All works are shelved according to their call numbers.
Every number corresponds to a science or discipline.
UDC is a decimal and hierarchical system. Conversely, the larger the UDC number, the narrower the subject. 159.920.1 The UDC number is the first filing element of the call number. It determines the physical arrangement of the work and classifies the work within a certain subject. It is not a good search strategy, however if the reader is looking for a specific book or journal, or if the reader is looking for works in a certain subject field.