04 The DDC hundred Divisions

Before we go on to list the thousand Dewey subject numbers and subject headings, let’s take a look at the broader structure. The DDC groups all subjects in TEN broad CLASSes, each starting with a round ‘hundreds’ number:

000      Generalities (Computer Science, Information, and General Works)

100      Philosophy and Psychology

200      Religion

300      Social Sciences

400      Language (and Linguistics)
500      Natural Sciences and Mathematics

600      Technology (Applied Sciences)

700      Arts (and Recreation)

800      Literature800 Literature

900      Geography and History (and Biography)

So these are the ‘Hundreds’. All the 900s – that means the numbers 900 to 999 - cover the field of Geography and History, and so on. Each of the Hundreds Classes is subdivided into ten DIVISIONS each (900 to 909, 910 to 919, and so on), each Division into ten SECTIONS. Ten Classes, into ten Divisions, into ten Sections each: totalling up to 10 X 10 X 10 = a 1000 Section numbers, a thousand subject heads.

I've put the hundred Divisions on their own Page...see the tabs at the top of the screen.

So where does the ‘Decimal’ in the DDC come in? That’s because the subdividing doesn’t stop here; the process goes right on, except that a decimal point is put after the 3-digit number. Thus 910 can be subdivided into ten sub-classes (910.0 to 910.9), each of these could be further divided into ten sub-sub-classes (910.90 to 910.99), and so on… to as many levels as we wanted. Strictly, the numbers ending in zero after the decimal point (like 910.0) are not given separate mention, so the total number of subdivisions may be 9, not 10 for each level. Each number is associated with an individual subclass of the main subject. This is usually set down in detail for each number, as each subject will be broken down in a domain-specific manner, but there are some broad conventions, such as .01 refers to the ‘philosophy’ or ‘theory’ of the main subject. There is in fact a Table of Standard Subdivisions, which we will describe later.