A call number acts like an address for the book and its letters and numbers will tell you where in the Swirlbul Library to find it.
To start, look at the letters at the on the first line of the call number. In the Swirlbul Library, the books are located as follows:
AC-DB Level 5S
DC-HD 999 Level 4S
HD 1000-KZ (Except M1-M3) Level 3S
M1-M3 1st Floor (across from 3S)
L-PN Level 2S
PR-PS Level C
PQ-ZA (Except PZ) Level S
PZ-Juvenile Level S, Level 5S
On the second line of the call number, the books are arranged in numerical order, from low to high.
On the third line, the letters are in alphabetical order and the numbers are read as a decimal (not a whole number). For example A.55 will be shelved before A.6
Finally, the last line is a number that represents the year of publication.