Dictionary and Classified Catalogues
For library catalogue both its outer or physical form and the inner form are equally important. The outer forms of a library catalogue comprise a bound or loose-leaf catalogue; a printed catalogue; a catalogue in machine-readable form and the like.
The inner form decides what particulars go into the entry and how the inner format of the entry is to be arranged. It also decides which one of the several access points is to be considered 'prime' or 'important' or 'main'.
For example, in a Dictionary Catalogue the author of a work is given importance. The main entry is given under the author. But in a Classified Catalogue the class to which the book belongs is considered important. What is meant by "a class" you have learnt in course BLIS 03. To recapitulate; "a class" is a group of items which have some characteristics in common.
The class to which a book belongs can be indicated by a letter or Roman alphabet or by a number or other symbols called notation. On Example 1 we have taken the book with the title.
ECONOMICS IN ONE LESSON
This book belongs to the class ECONOMICS. Its class notation according to Dewey Decimal Classification (DDC 19th ed.) is 330 and in Ranganathan's Colon Classification (CC 6th ed.) is X.
So, when subject approach or class approach is considered as the main access element the book can be entered under the following heading.
ECONOMICS
330 When the book is classified according to DDC
X When the book is classified according to CC
Thus, for the same book the Main Entry is given under the author Henry Hazlitt, (in actual practice the entry starts with the surname. The heading will be Hazlitt, Henry) in a Dictionary Catalogue, and under the notation 330 or X in a Classified Catalogue.