Wang Laboratories, Inc.

Arun K Agarwal

David R Lakness

Suzanne C Knapp

A task control structure for transferring tasks from a storage device to a system memory and for controlling execution of tasks, and a document manager for loading document information in the form of document data structures from the storage device to the system memory and managing access to the data structures by the tasks are using task control blocks to manage the execution of tasks and document control blocks to manage access to the document data structures by the tasks. Each document file has a document control block and the document files and the document control blocks are designed to represent and relate to the structure of documents. Each document file has at least one page including at least one area, each containing at least one type of information. Each area including, in an area containing text information, at least one column for containing text information including at least one line, each line including a string of at least one text character, a reference to attribute applying to the characters or the string, and references to external data items associated with the line. A screen manager is used for creating visual display screens, each screen having a virtual screen with one or more viewpoints onto data to be displayed. The screen manager includes a control structure containing information relating each screen to a corresponding task, and, for each screen, information describing certain properties of the screen, and information relating the screen to the data residing in the document structure to be displayed.

Screen manager multiple viewport for a multi-tasking data processing

A data structure for use in a document processing system corresponds to a document comprised of one or more Pages. Each Page is subdivided into one or more nonoverlapping Areas, each Area in turn being comprised of one or more types of Layers. Each Layer type is expressive of a particular type of information such as text or graphics information. Different Layer types may be superimposed to comprise the contents of an Area.

Data structure for a document processing system

In a multi-tasking data processing system, each task may request that the operating system set up descriptor blocks which identify virtual screens for display of data on the video display. Under keyboard control, only one virtual screen is selected for display at a given time. The operating system reserves a portion of the video display for displaying identifiers of the virtual screens which have been established but which are held in background. Each virtual screen may be subdivided into viewports by the corresponding application task. Those viewports are also identified in the operating system by descriptor blocks which point to pages of data in the document files. The descriptor blocks can be modified through requests from application tasks even when held in background. Whenever the display memory is updated, data designated by the descriptor blocks is passed through a rasterizer in the operating system which generates the pixel data to be stored in a display memory.

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Chelmsford, MA, United States of America

Arun K Agarwal