Letters are read alphabetically but numbers are read as decimals. Items with letters on this line are shelved before those with just decimal points and numbers. The last line may include the year of publication. This system is used for U.S. Government Publications housed on the first floor. SuDocs numbers may be written in a single line or vertically.
Numbers following decimal points are whole numbers.
Letters in a section are shelved before numbers in that section. They come before numbers and indicate editions of a publication. Periods, colons, or slash marks divide call numbers into sections. Each section is read separately. The first line , usually letters but sometimes including numbers, ends with a period.