1. A tactile access and navigation system for a visually impaired user operating within a computerized data environment, said system comprising: a. a bi-directional input-output system having at least one tactile display and at least one user-operable input control; b. a data transformer in communication with said at least one tactile display, operative to extract display data from the computer, and to transform extracted display data into a form suitable for display by said at least one tactile display; c. means for arranging the display data into a predetermined structure of GUI elements, said structure being navigable by said bi-directional input-output system; and d. means for providing display data to said at least one tactile display in accordance with predetermined modes of operation, which include: i. at least one viewing mode for displaying on said at least one tactile display a tactile representation of graphical and textual data content; and ii. at least one navigational mode for displaying on said at least one tactile display a tactile representation of the orientation of said GUI elements within said structure.