Help in reading a call number

Here is a call number to use as an example: PQ 90 .A213

1. All the books in the library are listed in alphabetical order by call number. For the example above, find the P section on the library shelves.

2. Next, again in alphabetical order, within the P section, search for for the letter Q.

3. The number next to PQ is in numerical order. Now, locate the section where 90 is.

4. The final part, after 90, is in decimal order.
Remember that the number .A213 is a decimal number, not A213 as a whole number.

    Example of a correct book order: .A2 then .A211 then .A23 then .A3 then .A3123

5. Go in order.

A. find the .2 section
B. then the .21 section
C. finally, the .213 section.

6. Lastly, some call numbers have a year of publication. They are shelved in order of year of publication. (This call number didn't have one).