Call numbers are arranged in alpha-numeric order, with some decimals thrown in along the way.  A typical call number might look like this:

Line one - contains either a single or a double letter.  For example, in the section for the H's, you will find books that begin with H, then HA, HB, HC, etc... all the way to HZ.

Books beginning with call numbers A-F are located on the third floor of the library building while those beginning with G-Z are located on the second floor.  All reference books are in the Reference department.  All oversize books are in the oversize collection.

Line two - is a whole number from 1 to 9999.  For example, in the section for the HG's, you will find HG 1, HG 2, HG 3, etc... all the way to HG 9999

Line three - is a decimal point followed by a letter and a number.  Books are shelved alphabetically according to the letter to the right of the decimal point.  For example, in the section for the HG 4057's, you will find .A then .B then .C, etc... all the way to .Z
 
If two books have the same letter on the third line, then the decimal numbers must be followed.  For example, .A217 is shelved before .A3 because .217 is a smaller decimal number than .3

Date - the call number may or may not include a date.  For example, 1997.

Volume - if there is more than one volume, the volume number will be included in the call number.