Minicomputers programmed in a high-level interactive language form a very attractive basis for the development of systems involving close man-computer collaboration. This paper is based on a wide range of experience of interactive minicomputer systems in commercial, medical, industrial, and scientific applications. It is first argued that the development of systems for effective man-computer collaboration requires not only interactive system use but also interactive system development. The designer needs to be able to tailor the system to user requirements at least partially as an experimental dialogue at a terminal with a user. There follows a critique of certain features of central computer utilities that limit their effectiveness in interactive applications, leading to a proposal for the use of minicomputer-based systems programmed, and used, interactively. We then give a number of case histories of our own experience in developing and using web systems in commercial, medical, and scientific applications From this experience, we have extracted a number of rubs for programming interaction between the user and computer system which we outlined. Finally, the main features of the software technology underlying these systems we briefly described.