G 55  Call Numbers  (was part of G 60)  (General)

BACKGROUND:  A call number consists of two main parts:  a classification number and a book number.  The classification number is normally selected from the LC classification schedules and reflects the subject matter of the book.  The book number serves to organize works on one subject (in one classification number) by reflecting, normally, an alphabetical arrangement by main entry or title.  Since 1982, monograph call numbers contain a third element, a date.

1.  Classification numbers

Classification numbers may consist of one, two, or three capital letters followed by up to four Arabic numerals, arranged in increasing order, and sometimes decimal or Cutter number extensions.

a.  Class letters.  Only 21 letters are used as initial letters:  I, O, W, X, Y are not used.  I and O are not used as second letters.  Any letter may be used in the third position.  Only two classes (D and K) use three letters.  D (History) uses three letters only for DAW and DJK.  K (Law) frequently uses the third letter.  In KE (Law of Canada) and KF (Law of the United States) the third letter represents province or state names mnemonically.

b.  Numerals.  Whole numbers are arranged in ascending order, as shown in this example from TH, Building construction.

c.  Decimals.  Decimal numbers are used when it is necessary to insert a new topic between two whole numbers.  Decimals may follow numbers of any length; there is no limit on the length of a decimal number.  Decimals do not necessarily represent a subtopic of the whole number.  They file as decimals.

Examples:

d.  Cutter numbers.  Cutter numbers representing topics or places may occur in the printed schedules after numbers of any length, including decimal numbers.  In the following examples, the term in bold-faced type is the basis of the Cutter number:

e.  Two Cutter numbers.  Cutter numbers that represent topics or places may also occur after other Cutter numbers of any length, including decimal numbers.

Example:

2.  Book numbers (author numbers)

Book numbers are added to classification numbers, normally to represent the main entry or the title, if no main entry is present.  These numbers are based on 1) instructions in the schedules, 2) works already in the shelflist under that class number, or, if no conflict, 3) the Cutter table in G 63.

a.  Single Cutter number for main entry.  If the class number consists of letters and numerals only, one Cutter number will usually be added, which is based on the main entry or title.  These class numbers will be followed by a single Cutter number, which, in the examples below, is in bold-faced type.

b.  Double Cutters (two Cutter numbers together).  If the class numbers contains a Cutter representing the subject matter or a single reserved Cutter, then a second Cutter number for the main entry or title is added.  These classification numbers will be followed by a second Cutter for the book number, here in bold-faced type.

Examples:

c.  Book number in the final digits.  If the class number requires two Cutters to represent the subject matter, then the works are arranged alphabetically but main entries are reflected in digits added to the second Cutter.  This "book number" is shown as the bolded "7" in the example below.

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General