In the Dewey Decimal classification system, books on similar subjects are grouped together by means of their call numbers.
The main Dewey Decimal classes are:
100 Philosophy and psychology
300 Social Sciences
500 Natural sciences and mathematics
600 Technology (Applied sciences)
700 The arts (fine and decorative)
800 Literature and rhetoric
900 Geography and history
Each class is further subdivided at the hundred divisions and the the thousand sections. Numbers are placed after a decimal point to further identify material more specifically by subject.
Fiction F Author Last Name (F Green)
Biography B Subject Last name (B ALI)