One of the first applications of the computer to information retrieval was in the production of printed indexes. Computers were used, both for the preparation of in-house indexes to reports, local abstracting and indexing bulletins, patent lists, etc., and also for the production of indexes for the major abstracting journals like Chemical Abstracts, Biological Abstracts, etc. Originally, indexing was an isolated operation. Now-a-days, indexes have become one of the range of database products.
Most of the indexes consist of a series of lead terms usually arranged in alphabetical order. Each lead term may be qualified and must have a link that leads the user to other lists or documents. Computer generated indexes mostly rely on automatically assigned index terms. They might also he based on intellectually (manually) assigned terms.