As with classification schemes, there are different catalogue codes available for use in libraries. Two of them are already known to you as they are prescribed for detailed study in Course IV. These are the Anglo-American Cataloguing Rules, Edition 2 (AACR-2) and the Classified Catalogue Code of Ranganathan, Edition 5 (CCC). The former is a more descriptive catalogue code and is mainly meant for a dictionary catalogue. The latter, on the other hand, is meant for a classified catalogue and is more simple, scientific and logical. Here again, the final choice of the code is governed by various factors like the internal form of the catalogue chosen, namely, classified or dictionary, the extent of bibliographical description needed, the code in use in associated libraries, if any, etc. Whichever is the code chosen, it should be consistently followed in all cases so that standardisation will be ensured in the choice and rendering of the headings and other sections, and in the order of citation.
If the choice happens to be in favour of AACR-2, there arises the need for choosing a list of Subject Headings too. There are two popular lists, namely, the Sears' List of Subject Headings and the L.C. List of Subject Headings. The former is adequate for a small library while a large library will need the use of the latter. Both of them are useful for general libraries while special libraries will need specialised lists. There are also different indexing techniques like PRECIS and POPSI. Chain indexing is the technique introduced by Ranganathan as part of the CCC primarily for use in a classified catalogue. These subject indexing techniques are discussed in Unit 6 of Course IV. Lists of Subject Headings or indexing Techniques are required for the cataloguer to choose headings for either class index entries in a classified catalogue, or specific subject entries and cross reference entries in a dictionary catalogue.