The most common systems in English-speaking countries are
Dewey Decimal Classification (DDC)
The 15th edition, edited by Milton Ferguson, implemented the growing concept of the “standard edition”, designed for the majority of general libraries but not attempting to satisfy the needs of the very largest or of special libraries.[23] It also reduced the size of the Dewey system by over half, from 1,900 to 700 pages.
Library of Congress Classification (LCC)
Libraries in the United States generally use either the Library of Congress Classification System (LC) or the Dewey Decimal Classification System to organize their books. Most academic libraries use LC, and most public libraries and K-12 school libraries use Dewey.
Colon classification (CC)
he first edition of colon classification was published in 1933,[1] followed by six more editions. It is especially used in libraries in India.
Universal Decimal Classification (UDC)
In 1933, the bibliographic edition became the Universal Decimal Classification, which left the library and abridged versions as the formal Dewey Decimal Classification editions.
The Universal Decimal Classification (UDC) is a bibliographic and library classification representing the systematic arrangement of all branches of human knowledge organized as a coherent system in which knowledge fields are related and inter-linked.
EUROPE (41) A Albania, Andorra, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Repubic, Estonia, Hungary, Latvia, Liechtenstein, Lithuania, Macedonia, Moldova, Montenegro, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Ukraine
B Belarus, Belgium, Denmark, Finland, France, Norway, Russian Federation, Sweden, Switzerland
C Austria, Faroe Islands, Germany, Greece, Iceland, Ireland, Italy, Malta, The Netherlands, United Kingdom