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Universal Decimal Classification (UDC)

1. Introduction: The first international conference on Bibliography held in 1895 at Brussels. Its recommendations helped in the establishment of Institut International de Bibliographie (IIB). On the initiation of two Belgians- Paul Otlet and Henry La Fontaine, the Institut International de Bibliographie sponsored a project for the preparation of Le RĂ©pertoire Bibliographique Universel. This meant the preparation of classified card index to all published information.
The Decimal Classification (D.C.) was first published in 1876. In order to use a classified arrangement for the index, the two Belgians, chose the 5th Edition of Dewey Decimal Classification (DDC) (1894) devised by Melvil Dewey as the basis. As a result, the first complete international edition of UDC was published in French language in the year 1905 entitled Manuel du RĂ©pertoire Bibliographique Universel.
The Institut International de Bibliographie (IIB) became the Institut International de Documentation (IID) in the year 1931 and in 1937, Federation Internationale de Documentation (FID). The Classification Department of the FID (FID/CID) at the Hague is responsible for the revision and development of the UDC.
            The work on the 4th edition, in English language entitled the Universal Decimal Classification began in 1940 under the auspices of the British Standard’s Institute (BSI). The first schedules were published in 1943. The abridged edition B.S. 1000A was first published in 1948 in response to a widespread demand for a comprehensive short edition in English.

2. Principles: Three basic principles are evident in UDC.
a) Classification: UDC is a classification in the strictest sense, depending on the analysis of idea content, so that related concepts and groups of concepts are brought together.
b) Universal Classification: UDC includes every field of knowledge.
c) Universal Decimal Classification: UDC constructed on the principle of proceeding from the general to the more particular by the arbitrary division of the whole of human knowledge into ten main branches and each further subdivided decimally to the required degree.

3. Structure: The whole field of human knowledge, regarded as unity, is divided into ten main branches denoted by decimal fractions. For convenience, the initial decimal point is omitted, thought it is the fact that all UDC are in reality decimal fractions less than unity that determines the sequence of numbers, which otherwise seems chaotic. On the other hand, purely as visual aid, “points” are inserted usually after every third figure. The main classes of UDC are-
.0         Generalities
.1         Philosophy
.2         Religion
.3         Social Sciences
.4         Language
.5         Pure Science
.6         Applied Science
.7         The Arts
.8         Literature
.9         Geography

4. Symbols:  In UDC, the following symbols are used in between two or more numbers.
1. + (plus or and sign) means commonly associated concepts.
2. It may be used to connect two or more separated (non consecutive) UDC numbers, especially when they denote commonly associated concepts.
Slash or Stroke
1. / (slash or stroke) sign means “from .. to..”.
2.  It is used to join the first and the last of a series of consecutive UDC numbers denoting a range of concepts.
3. Common numbers is omitted in writing the UDC numbers.
1. : (colon) means relation.
2. The colon sign is used generally to link two or more UDC numbers denoting related concepts of equal value.
3. Whenever doubt arises it is better to use + (plus) symbol.
4. When the relationship involves a subordinate concept for which no separate entry is required by reversal, [] (square bracket) may be used in place of: (colon).

5. Auxiliary Notation: Auxiliaries are a means of eliminating repetition in all parts of the printed main tables, in that they group certain recurring and generally subordinate concepts, such as language, form, place, time and point of view. They do not stand alone, but are attached to the main UDC number denoting primary subject-matter. - (dash), .0 (dot naught), ‘ (apostrophe) are considered as special auxiliary subdivisions.
a) Common Auxiliaries: The common auxiliaries are mentioned below-
1. = (equal) symbol means language.
2. The equal symbol is used to designate the language or linguistic form.
Naught followed by Arabic numeral in parentheses
1. (0..) naught followed by Arabic numerals in parentheses means form.
2. The naught followed by Arabic numerals in parentheses serve to distinguish the form in which the subject denoted by the preceding main number is presented.
Arabic numerals in parentheses
1. (1/9) Arabic numerals in parentheses means place.
2. Arabic numerals in parentheses used to indicate the geographical range of the subject denoted by the preceding main number.
3. When the geographical or regional aspect is paramount, entry may be made under the auxiliary, which then precedes the main umber.
Equal symbol followed by Arabic numeral in parentheses
1. (=..) equal symbol followed by Arabic numeral in parentheses means race and nationality.
2. Equal symbol followed by Arabic numeral in parentheses serve to indicate the racial aspect of the subject.
Arabic numerals in quotes
1. “..” Arabic numerals in quotes mean time.
2. Dates before Birth of Christ (B.C.) is represented by prefix – (minus). Example: 69 BC is represented as “-0064”
3. Christian Era (A.D.) is represented after giving a prefix + (plus). Example: AD 90 is represented as “+0090”.
4. Centuries are represented by a two figure notation. Example: 19th Century is represented as “18”.
5. Decades are represented by a three figure notation. Example: 1930s is represented as “193”.
6. The YYYY.MM.DD pattern is used to mention a particular date. Example: 30th March, 2015 is represented as “2015.03.30”.
7. Period embracing several centuries, decades or years are denoted by the initial and final figure separated by / (slash) sign. Example: 17th to 19th Century is represented as “16/18”
Point naught naught
1. The symbol .00 (point naught naught) is used to express a subject when looked at from a particular aspect or point of view.
2. The symbol .00 (point naught naught) is never used alone, but added to a main class number.
3. The general sign : (colon) which exhibits any kind of relation can also be used instead of the symbol .00 (point naught naught), but its use is avoided because it creates more confusion in the file of the document.
4. It is advisable to use a different class when a concept is available there. Example: Engineering Accounts is represented as 62:657.4 instead of 62.003.3.
5. Symbol .00 (point naught naught) should not be confused with the main UDC division 001/009 (Generalities).

b) Special Auxiliaries: The special auxiliaries are mentioned below
A to Z
1. The A-Z (alphabetic device) is used to specify or individualize the subject by names. To do this appropriate names or initials within brackets or without brackets are used.
2. The alphabetic device is used mainly in biographies and literature works.
Point naught
1. The symbol .0 (point naught) is used under 06, 22, 331, 34, 53, 624, 654, 656, 66, 67 and 7 as an integral part of the schedule of the abridge version of the UDC itself.
1. -03 is used to indicate material or constituents of which objects or products are made generally in 66 and 67 classes.
2. -05 denote person and are also integrated as part of the schedule of the abridge version of the UDC itself.
3. –3 is used (hyphen) under 54, 621 and 622 and is integrated in the schedule of abridge version of UDC itself.
1. The symbol ‘ (apostrophe) is used to get a compound number for substances derived from two or more components.
2. The symbol ‘ (apostrophe) usually replaces certain main number figures common to each components. In case when it is used the instructions are given the schedule. Example: Lime Silica Glass is represented as 666.113’41’28 instead of 546.41 546.28 666.113
3. In case of -03 material, when more than one material is to be represented then the second material is represented by symbol ‘ (apostrophe) instead of repeating -03.
4. The symbol ‘ (apostrophe) is limited to a few schedules in UDC and not detailed in the abridge edition of UDC. It is widely used in metallurgy and chemistry.
1. When the listed UDC auxiliary for place are unsuitable for specialist use, an established non UDC regionalization schemes may be introduced after an asterisk within the bracket, provided that reference is made to the scheme adopted in a footnote or introduction. Example: British Bird Distribution by Vice Countries is represented as 598.2(42*..)
Square Bracket
1. [] (square bracket) is used when two or more UDC numbers are linked by +, / or : and as a whole related to another number by : (colon).
            An auxiliary should not be used for a concept which can be denoted by a simple main number, or by two number linked by : (colon) sign.
            More than one auxiliary is seldom necessary. When two or more auxiliary have to be used with a simple main number, the generally accepted order is
Special auxiliary .01/.09  -0/-9
Viewpoint 00
Place (1/9)
Time “”
Form (0)
Language =

6. Using UDC: The following points will help one to classify the document by using UDC.
a) Accustom with UDC: Try to grasp of the principles and notation of the UDC system.
b) Identify the Subject of the Document: Find out the general background knowledge of the subject matter to be classified. In determining the subject never relies on the title alone, look into abstract, content page or go through the text of the document.
c) Consult Printed Index: The alphabetical index is an invaluable preliminary aid to find out the probable number.
d) Verify with Schedule and or Auxiliary Table: To arrived at the UDC number never rely on the printed index alone. Verify the number of the index with the main schedule or auxiliary tables by going to the broader aspect or narrower areas.
e) Do not Hesitate to Assign More Than One Number: If the document present several distinct subjects or aspect of a subject, it is good to assign more than one number. In case of more than one UDC number, choose the one which corresponds most closely to the users’ requirement.

7.  Advantages of UDC: UDC is being used by all types of libraries for book classification, indexing and information retrieval purposes, and it is estimated by different authors that it is being used by about 1,50,000 libraries in 130 countries of all types and Information centres.
a) UDC Advantage: Because of UDC adapting the DDC, the libraries classifying with DDC could use the UDC whenever there was need to use extensions of the DDC.
b) Faceted Classification: The advantage in the UDC being that it is a faceted classification and has far greater functional capacities than any other scheme of classification.
c) UDC is Compulsory in Certain Countries: In certain countries like USSR, it is an officially prescribed system for classifying documents in science and technology, whereas in countries like UK, Hungary, etc it is issued as an official standard.
d) Practical Oriented: Any item once coded and filed correctly by using UDC can be readily found from whatever angle it is sought.

8. Conclusion: Universal Decimal Classification (UDC), which was designed to facilitate the organization of a universal bibliography of all recorded knowledge. Initially UDC was based on the fifth edition of the Dewey Decimal Classification that combines notation to express multiple concepts. The Universal Decimal Classification system is issued by the International Federation for Documentation, in the Hague, Netherlands, which is responsible for its ongoing revision.

How to Cite this Article?
APA Citation, 7th Ed.:  Barman, B. (2020). A comprehensive book on Library and Information Science. New Publications.
Chicago 16th Ed.:  Barman, Badan. A Comprehensive Book on Library and Information Science. Guwahati: New Publications, 2020.
MLA Citation 8th Ed:  Barman, Badan. A Comprehensive Book on Library and Information Science. New Publications, 2020.

Badan BarmanBadan Barman at present working as an Assistant Professor in the Department of Library and Information Science, Gauhati University, Guwahati-781014, Assam, India. He is the creator of the LIS Links ( - India’s most popular social networking website for Library and Information Science professionals. He also created the UGC NET Guide ( and LIS Study ( website.

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