What are Call Numbers?

Call numbers are what we use to organize books on the shelves. They're basically just a way of indicating a book's subject and author in a condense way. There are a few different kinds of call numbers, but here at Snell we use Library of Congress. Complete the tutorial below that will introduce you to Library of Congress call numbers. These numbers can look very intimidating at first, but don't worry: as long as you can put them in alphabetical and numerical order, you'll be fine. In other words, if you know your alphabet, and you can count, you are set!

Once you've completed the tutorial and emailed your supervisor, you're ready to work! The next tab will tell you what to do for your first shift and beyond.

Snell Library uses the Library of Congress call number system to organize its books and media items.  An item’s call number is like its “address”; it indicates where it can be found in the library, and where it falls on the shelf in relation to the items around it.  Call numbers can be found on the spine or lower left-hand area of the front of an item.  The components of a call number are arranged vertically:

  

 

LC call numbers are alphanumerical; they are organized first by letter and then by number.  

The first line of a call number is alphabetical; it contains a letter or letters that indicate the general subject area the item should be shelved under.  Call numbers starting with single letters precede call numbers with multiple letters.  For instance, call numbers beginning with just the letter P come before call numbers starting with PA, PN, PS, etc:

 

P             >        PN        >         PS 

1000                 59                   350

.A54                 .W35               .A35

1934               1998                 .T7

                   1975

 

The second line of a call number is numerical, and it tells you where the item falls within the previous alphabetical range.  This number should be read as a whole number, with the smallest numbers shelved first and the larger numbers coming after.  For instance, call numbers starting with PS 350 come before call numbers starting with PS 1150, and call numbers starting with PN 45 come before call numbers starting with PN 1995, and so forth:

 

PS               PS               PS                                PN                PN            PN 

350      >     1150     >     3500                             45          >     250      >   1995

.A35            .A2              .G78                             .B392            .A21          .M55

.T7              1995            .D11                             1994             .G75          2007                                 

1975                               1964                                                 1989

 

The following lines are called cutter numbers, which further classify the item according to specific topic, author name, etc.  Cutter numbers are alphanumerical, which means they contain a letter followed by one or more digits.  These digits are read as decimal numbers rather than whole numbers.  For instance, call numbers beginning with PS 350 .A3655 would be shelved before those beginning with PS 350 .A373, which would be shelved before the ones beginning with PS 350 .A4, and so forth:

 

PS                 PS                PS                           PS                  PS                PS

350               350               350                          350                 350               350

.A3655    >  .A373     >     .A4                           .A3655           .A3655         .A3655

.T7                1995             .D11                         .T7         >      .T75       >    .T9

1975                                  2009                        1975              2001             1969

 

The last line of a call number is often the date of publication.  If there are two editions of the call number PR5397 .F7, they might be listed as PR5397 .F7 1992 and PR 5397 .F7 1993.  The edition with the earlier date comes first on the shelf.  Occasionally different editions with the same call number and same publication date will include an extra letter after the date to distinguish them.  For instance, PN1995.9 .W4 T74 2011 precedes PN1995.9 .W4 T74 2011b. 

Another rule of thumb for LC Call numbers is “nothing comes before something.”  For example, if an item’s complete call number is PS 350 .A35, it comes before the call number PS 350 .A35 1992, since the first call number has nothing in the date field following the first cutter number.  

Likewise, PS 350 .A35 1992 comes before PS 350 .A35 .T7 1975 because even though it has a later date, it has no value (nothing) in the field corresponding to the second cutter number, which would precede the date.

 

PS               PS              PS 

350    >        350  >        350

.A35            .A35           .A35

                   1992          .T7

         1975 

Dissecting a call number:

PN         } first line (alphabetical)

1995.9  } second line (numerical – read as whole number)

.W4       } next line (cutter numbers – read digits as decimals)

.T74       } next line (cutter numbers – read digits as decimals)

2011      } publication date (if there is a date, earliest date comes first)