A digital image-processing system based on a minicomputer has been developed, which is especially suitable for man-machine conversational image processing. This system features parallel connections of the main memory of a computer with a central processor unit, a detector and a cathode ray tube monitor by the direct memory access channel. By the time-shared operation of memory access, this system provides a human observer with not only an image after processing but also the image in the course of processing or detection, without flicker. Applicability of this system to man-machine conversational image processing is demonstrated through restoration of a defocused image and the extraction of subtle structures within an x-ray photographic image.