Reading Library of Congress Classification Numbers
The first line of a Library of Congress call number begins with one or two letters. These letters should be read in alphabetical order. A call number that begins with A is shelved before one that begins with B, and a call number that begins with QE is located some distance before one that starts with QK.
The second line of a call number consists of one or more numbers. This line is read in numerical order, so that a smaller number precedes a larger number.
The third line is the most difficult part of the call number. The letter following a period is shelved alphabetically, thus:
However, the number on this third line is read like a decimal. Thus, these examples are in correct call number order:
This makes sense if you read these numbers as decimals!
The final line of a call number may include a date, volume indicator, issue number, copy number, or other annotation. These are shelved in numerical order following the preceding lines as shown below.