The organization and formatting of hierarchical displays for the on-line input of data

On-line terminals, which we shall call "list selection terminals," are being investigated here and elsewhere as input devices for information systems. These display lists of alphanumeric entries from which a user may select entries by pointing. Whereas users of most terminals (including ours) point with a light-pen, users of the Control Data Digiscribe select by touching electrically conductive regions on the faceplate with a finger, thus completing a radio-frequency circuit. The lists are displayed on either a cathode ray tube or an optical rear-projection screen, and they may be changed rapidly under computer control. The user composes input to the system by selecting words and phrases from the lists. As he proceeds, new lists are displayed as required.