Introduction

Since the 20th Edition (1989), print versions of the full DDC have constituted four volumes. A typical arrangement of a printed DDC is as follows:

• • Volume 1. The first volume begins with the prefatory and introductory material, including the Introduction, a sort of operational manual to the DDC. This volume also includes the Manual and six auxiliary tables. In printed editions 20–23, Volume 1 was typically smaller than the rest; in the print-on-demand (PoD) publications, the volumes are more equally sized. Consequently, PoD versions also include the first two main classes (000–199).

• • Volumes 2–3. These two volumes are exclusively devoted to the schedules of classes. The schedules are arranged in numerical order and the section number of three digits is always printed twice at the left and right top of every page, facilitating scanning of the schedules by class numbers instead of just page numbers. The schedules are in the form of entries, with a class number on the left and its right a caption, i.e. the verbal content of the number. Hierarchical relations among subjects are shown on the left by the length of the class number and the shifting of indentation of the captions to the right. Under many of the class numbers, there are a variety of notes of explanations and instructions. These notes are essential to assign and build correct and consistent class numbers. In editions 20–23, Volume 2 featured classes 000–599; in the PoD, 200–599. Volume 3 has remained constant, with classes 600–999 since 1989.

• • Volume 4. The Relative Index (see Chapter 15).

Types of entries

All the approximately 40,000+ entries in the schedules may be divided into six categories:

• 1 Ordinary entries

• 2 Unusable headings

• 3 Unassigned numbers

• 4 Optional entries

• 5 Hook numbers

• 6 Centered headings.

Ordinary entries

The majority of the entries in the schedules are ordinary entries: a number with a corresponding heading which may or may not have notes or instructions. These can be directly applied to relevant works. Unusable headings

As a consequence of revision, a class may be relocated to some other place, or otherwise discontinued. In such cases, part of the number is enclosed within square brackets, e.g. 296[.06] Organizations and management [of Judaism]. Such numbers have instructions directing a classifier where to class works that otherwise might have gone there.