| Type (indicator) | Description | Example (number and caption) |
|---|---|---|
| Built number (B) | Indicates a record for a number constructed according to add instructions stated or implied in the schedules or tables. | B 598.16 Flightless birds |
| Centered entry (C) | Represents a subject covered by a span of numbers. A centered entry is used to indicate and relate structurally a span of schedule numbers that together form a single concept. In add tables, a greater-than symbol (>) precedes a centered entry. | C 930-990 History of ancient world; of specific continents, countries, localities; of extraterrestrial worlds |
| Table centered entry | Represents a subject covered by a span of numbers. A table centered entry is used to indicate and relate structurally a span of table numbers that together form a single concept. | C T2--4-T2--9 The modern world; extraterrestrial worlds |
| Manual entry (M) | Indicates a record for an entry in the DDC Manual. | M 361-365 Social problems and services |
| Number in square brackets [ ] | Indicates a number that has been discontinued or relocated, or an unassigned number. Record instructs you not to use this number and provides a cross-reference to the correct class number. |
[104] Unassigned 511[.22] Intuitionistic mathematics [291] Comparative religion T5--[04] Persons of mixed ancestry with ethnic origins from more than one continent |
| Number in parentheses ( ) | Indicates a class number that is an optional alternative to the number usually assigned to a concept. | (921) Philosophers and psychologists |
| Footnoted caption (caption preceded by * or † and/or ‡) | Indicates that a record contains a reference to a footnote marked with that symbol. | *Administration of general forms of control †Latin dramatic poetry and drama ‡*Visual programming |
| Caption followed by ellipses | Occurs only with some built numbers. Indicates that the caption given is one of a series of Relative Index terms associated with that number. |
B 809.4 Essayists (literature), . . . |
| Number followed by ellipses | Indicates standard subdivisions and topics that use 0 instead of 1-9 to indicate their position in the hierarchy. | 004.0 . . . Standard and special subdivisions |