A user interface study concerning the usage effectiveness of selected retrieval modes was conducted using an experimental text retrieval system, TeSS, giving access to online documentation of certain programming tools. Four modes of TeSS were compared: (1) browsing, (2) conventional boolean retrieval, (3) boolean retrieval based on Venn diagrams, and (4) these three combined. Further, the modes of TeSS were compared to the use of printed manuals. The subjects observed were 87 computer science students who solved a number of information retrieval tasks in an area of computing new to them. In the experiment the use of printed manuals is faster and provides answers of higher quality than any of the electronic modes. Therefore, claims about the effectiveness of computer-based text retrieval have to be wary in situations where printed manuals are manageable to the users. Among the modes of TeSS, browsing is the fastest and the one causing fewest operational errors. On the same two variables, time and operational errors, the Venn diagram mode performs better than conventional boolean retrieval. The combined mode scores worst on the objective performance measures; nonetheless nearly all subjects prefer this mode. Concerning the interaction process, the subjects tend to manage the complexities of the information retrieval tasks by issuing series of simple commands and exploiting the interactive capabilities of TeSS. To characterise the dynamics of the interaction process two concepts are introduced: threads and sequences of tactics. Threads in a query sequence describe the continuity during retrieval. Sequences of tactics concern the combined mode and describe how different retrieval modes succeed each other as the retrieval process evolves.