With the development of magnetic discs, the capability to access data in a. random fashion (rather than in the sequential fashion with magnetic tapes) became possible. Also, due to the advances made in technology magnetic discs were available, at comparative low prices, to store large quantities of data. The advent of cheaper computers, and time sharing systems enabled several users to use a given computer at any given time. The development of visual display terminals enabled fast interaction with a remote computer. It was no longer necessary for a user to physically go to the computer to get a job done. He could enter data and program sitting in his room with his terminal and also see the results on his screen.
Large capacity discs, video display terminals and time sharing systems paved the way for the development of interactive retrieval systems. With these developments, it has become possible for the searcher (user) to access the database files at any time. It has also enabled him to formulate his search query in a step-by-step fashion. It is possible for the user of an interactive system to browse the document file and this helps him reformulating his search depending on the kind of references his search query has retrieved up to a given point of time in the search process and assessing the relevance these references to his information needs. Browsing is also possible with the thesaurus file which may facilitate him in the choice of appropriate terms to formulate his query.