The Alphadecimal Library Classification System (ALiCS)

The Alphadecimal Library Classification System is a system of classifying books in a library or collection, which I have devised to catalogue my small home library. (Examples of library classification systems are Library of Congress and Dewey Decimal.) I have long struggled to find a simple system to classify my small library of books that was not too complex, had memorable main class codes and was flexible enough to handle the specific “demographics” of the books in my library. I also wanted each book’s call number to have the same number of symbols, as opposed to variable length of call numbers in other systems. I could have just used the three-digit main classes of the Dewey Decimal system, of course, but this would have meant that some classes would be too specific for subjects not present in my collection, and not specific enough for other subjects. For example, I have a large number of sports books and I wanted the classes to be specific for different sports, but using Dewey all the sports books would have been under the same class.

I also wanted a system with letters at the beginning, as I find these more memorable than a purely numerical system. I initially used the Library of Congress (LOC) system, partly because, at the time (around the late 1990s), the Library of Congress was the only place with a comprehensive online search, which was also free to use. So, all my books were classified using this system.

There were a number of problems with this system, however. For one thing, the classifications were rather lengthy for the size of the library. Also, the resulting call numbers were of varying length and it was also difficult to class books that were not present in the Library of Congress catalogue. So, I was looking for a different system, with a fixed number of say five or six characters. I decided to devise one of my own but this is not an easy task, and I have relied upon some online resources to devise my system, in particular the Free Decimal Correspondence (FDC), created by John Mark Ockerbloom, and the Melvil Decimal System (MDS) devised by the users of LibraryThing, an online resource for cataloguing personal and small libraries.

The system I have devised is called ALiCS (a play on my own name ‘Alex’), which stands for the Alphadecimal Library Classification System. The ‘Alphadecimal’ description refers to the fact the main classes are represented by two letters, and these are followed by three numbers to complete the basic classification for each book. The two letters correspond in most cases to the first two numbers in the FDC, but in some classes they refer to the first three numbers. For example, whereas ‘AR’ (Architecture) represents the FDC class ’72x’, ‘RS’ (Sports and athletics) represents the class ‘796’. This is because of the high number of sports books that I have, as mentioned above. Indeed, the “Recreation and Amusements” class, which comes under “Arts” in the FDC, has its own main class in ALiCS.

How does it work?

The ‘Call Number’ for each work is split into two parts: a. the class number and b. one or two Cutter numbers.

The class number comprises the five-digit code determined by the subject matter of the book, e.g. HE315, which is the classification of ‘History > Europe > Germany > North Eastern Germany > Brandenburg’, or GE110, which is ‘Geography > Europe > British Isles > Scotland’.

The second part of the call number comprises one or two ‘Cutter numbers’, a letter followed by one or more digits. This is a very flexible way of adding further information to the classification, requiring no lengthy special tables and is easy to devise, and consist of a single letter followed by one or more numbers. (Cutter numbers are named after Charles Ammi Cutter, who devised them as part of his Expansive Classification. See below for details of how the Cutter system works.)

Usually, the class number is followed by one Cutter number, with a dot or period in between, and the Cutter number is used to determine the “shelf position” of the work within its subject class. This usually stands for the title of the book or the author’s name. For example, the book “Scottish Place-names” by W. F. H. Nicolaisen could have the call number GE110.N5, where the Cutter number is for the author’s surname.

Sometimes, however, the first Cutter number has to be used to add further specificity to the subject matter denoted by the class number. For example, for the book ‘Faust’s Metropolis: A History of Berlin’, with the class number HE315 mentioned above, would need to be followed by the Cutter number .B4 to specify that the subject matter relates to the city of Berlin. In this case, a second Cutter number may be added, say, for the title, and so the full call number would be HE315.B4 F3. Call numbers never have more than two Cutter numbers.

Other information may be included in the call number, for example the year of publication, but this can be omitted if space is at a premium. An example in the above case would be HE315.B4 F3 1999.


If possible the elements of a call number should be arranged vertically, as in the following example:

vertical style label

However, in my library, due to the type of labels, the printer being used and general space restrictions, the labels are arranged as below:

horizontal style label

ALiCS Main Classes

The following list shows the main classes in the ALiCS:

Class Subject FDC equiv
A — Arts
AA General arts 700—709
AD Drawing; Decoration; Design 740—749
AF Photography 770—779
AG Graphic arts; Engraving 760—769
AL Landscape gardening 710—719
AM Music 780—789
AP Painting 750—759
AR Architecture 720—729
AS Sculpture 730—739
B — Literature
BA General literature 800—809
BE Literature of Indo-European languages of Europe 810—889,
BH Literature of Indo-Iranian languages 892
BJ Literature of Caucasian & other languages 899
BK Literature of East Asian languages 895
BN Literature of North American indigenous languages 897
BP Literature of South American indigenous languages 898
BS Literature of Afro-Asiatic languages 893, 896
BT Literature of Turkic, Finno-Ugric & Dravidian languages 894
BV Literature of Austro-Asiatic languages & languages of Oceania 899
BX Literature of other languages & artificial languages 899
E — Religion
EA General religion 200—209
EC Christianity 220—289
EH Religions of Indic origin 294
EJ Judaism 296
EM Islam & Bahá’i faith 297
ET Natural theology 210—218
EX Other religions & comparative religion 290—293,
EZ Zoroastrianism 295
G — Geography, Voyages & Travels
GA General geography, voyages & travels 910
GC Geography of the ancient world 913
GE Geography of Europe 914
GF Geography of Africa 916
GH Historical geography 911
GM Maps & atlases 912
GN Geography of North America 917
GP Geography of South America 918
GS Geography of Asia 915
GX Geography of other areas 919
H — History & Biography
HA General history & biography 900—909
HB Biography 920—929
HC History of the ancient world 930—939
HE History of Europe 940—949
HF History of Africa 960—969
HN History of North America 970—979
HP History of South America 980—989
HS History of Asia 950—959
HX History of other areas 990—999
L — Language
LA General language 400—409
LB Linguistics 410—419
LE Indo-European languages of Europe 420—489,
LH Indo-Iranian languages 492
LJ Caucasian & other languages 499
LK East Asian languages 495
LN North American indigenous languages 497
LP South American indigenous languages 498
LS Afro-Asiatic (Hamito-Semitic) languages 493, 496
LT Turkic, Finno-Ugric & Dravidian languages 494
LV Austro-Asiatic languages & languages of Oceania 499
LX Other languages; Artificial languages 499
N — Natural Sciences
NA General science 500—509
NB Botany 580—589
NC Chemistry 540—549
NF Physics 530—539
NG Geology; Earth sciences 550—559
NL Life sciences 570—579
NM Mathematics 510—519
NP Palaeontology 560—569
NR Astronomy 520—529
NZ Zoology 590—599
P — Philosophy
PA General philosophy 100—109
PD Ideology; Philosophical systems 140—149
PE Ethics 170—179
PF Modern philosophy 190—199
PH Philosophy of humanity 120—129
PL Logic 160—169
PM Metaphysics 110—119
PN Ancient, mediaeval & eastern philosophy 180—189
PP Parapsychology 130—139
PS Psychology 150—159
R — Recreation & Amusements
RA Amusements 790
RC Card games; Games of chance 795
RF Fishing; Hunting; Shooting 799
RG Games & indoor amusements 793
RH Horsemanship; Animal racing 798
RK Games of skill 794
RP Public entertainment 791
RS Sports & athletics 796
RT Theatre; Dance 792
RW Water & Aerial sports 797
S — Social Sciences
SA General social sciences 300—307
SC Customs & folklore 390—399
SD Education 370—379
SE Economics 330—339
SG Statistics 310—319
SL Law 340—349
SM Public administration; Military science 350—359
SP Political science 320—329
SS Social service; Societies 360—369
ST Transport; Communications; Commerce 380—389
T — Technology
TA General technology 600—609
TB Building 690—699
TC Chemical technology 660—669
TE Engineering 620—629
TF Manufacturing 670—679
TG Agriculture 630—639
TH Home economics 640—649
TM Medicine 610—619
TP Occupations & handicraft 680—689
TX Business 650—659
X — General Works & Information Sciences
XA General information; Computing 000—006
XB Bibliography 010—017
XE Encyclopaedias 030—039
XJ Journalism; Newspapers 070—079
XL Library science 020—028
XP Periodicals 050—059
XQ Quotations; Anthologies 080—089
XR Rare books 090—099
XS Societies; Associations 060—069

A lookup table of F.D.C. main headings to A.Li.C.S. subject codes can be downloaded here (opens in a new tab).

Version 1.1 of the full schedule of the A.Li.C.S. system is available here (opens in a new tab).

Cutter Numbers

The standard Cutter system used by the ALiCS is as follows:

1. After initial vowels:

For the second letter: b d l-m n p r s-t u-y
Use number: 2 3 4 5 6 7 8 9

2. After the initial letter ‘S’:

For the second letter: a ch e h-i m-p t u w-z
Use number: 2 3 4 5 6 7 8 9

3. After the initial letters ‘Qu’:

For the second letter: a e i o r t y
Use number: 3 4 5 6 7 8 9
For initial letters Qa-Qt, use: 2-29            

4. After other initial consonants:

For the second letter: a e i o r u y
Use number: 3 4 5 6 7 8 9

5. For additional letters:

For the third letter: a-d e-h i-l m-o p-s t-v w-z
Use number: 3 4 5 6 7 8 9

For numbers, use the number range ‘A12-A19’.

Other notations can also be used, e.g. ‘v.1’, ‘v.2’ for volume numbers, and ‘c.1’, ‘c.2’ for copy numbers of the same work.

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ALiCS v1.1.9 © Alex Middleton, 2019.

The ALiCS system is open source and it can be used or modified for personal purposes. An acknowledgement would be appreciated, however. ALiCS is based upon and takes much of its information from the Free Decimal Correspondence by John Mark Ockerbloom, and MDS (Melvil Dewey System), an adaptation of the FDS used by members of LibraryThing to classify their books. The Dewey Decimal System is copyright of the OCLC.