Digital data display system

• US 4,451,825 A
• Filed: 12/09/1982
• Issued: 05/29/1984
• Est. Priority Date: 09/27/1979
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Johnson, Peter W., Quarendon, Peter, Hardiman, Raymond, Tuffill, Harold W., Hall, Stephen T.
• Primary Examiner(s): TRAFTON, DAVID
• Application Number:
  US06/448,159
• Time in Patent Office: 537 Days
• Field of Search: 340/735, 340/748, 340/750
• US Class Current: 345/467
• CPC Class Codes: G09G 5/225 comprising a loadable character generator character generators per se G09G5/24

Abstract

A digital data display system in which the display device includes a plurality of random access stores into which character cell definitions are loaded from a remote central processing unit. A character cell may be a 9×16 picture element matrix and each is defined in the CPU according to the requirements of a display request received from a users application program. The system control services include a graphics manager and graphics routines which construct a character buffer and character cell definition table according to the picture to be displayed. A character cell definition that is required more than once in a picture is only included once in the definition table, the character buffer having the required number of pointers to the one definition. When the character buffer and character definition table have been constructed, they are transmitted to the display device using a data communication system. The system can be used for color or monochrome displays.

Claims

1. A digital data display system for presenting a graphical picture on an output device in which the area or screen from which the picture is to be viewed is notionally divided into a plurality of character cells each of which comprises a predetermined number of picture elements (pels), the system comprising

first means for creating, in response to input information, a first level description of all the elements of a picture to be presented,

second means for storing a screen definition table having an entry for each character cell of the display area,

third means for calculating for each element of the picture, the pattern of pels in associated character cells required to display the elements, storing the calculated pattern in a table in a character cell store and associating the respective entry in the screen definition table with the required pattern in the character cell store,

fourth means to determine when a particular character cell pattern has already been calculated as required for a picture and to associate the respective screen definition table entries with only one copy of the particular character cell pattern, and

fifth means for transferring the screen definition table to a screen definition buffer store and the character cell pattern table to a character cell buffer store in the display device,

whereby the contents of the screen definition buffer store and character cell buffer store control the construction of a picture presented by the display device.

2. A digital data display system as claimed in claim 1 in which the display device includes a first plurality of random access storage devices for storing the character cell patterns and a second random access storage device for storing the screen definition table.

3. A digital display system as claimed in claim 2, including

a central processing unit having means for creating, in response to input information, a first level description of all the elements of a picture to be presented, means for storing a screen definition table having an entry for each character cell of the display area, means for calculating for each element of the picture the pattern of pels in associated character cells required to display the elements, storing the calculated pattern in a table in a character cell store and associating the respective entry in the screen definition table with the required pattern in a table in the character cell store, means to determine when a particular character pel pattern has already been calculated as required for a picture and to associate the respective screen definition table entries with only one copy of the particular character cell pattern,

and in which the display device is at a location remote from the central processing unit and the screen definition table and the character cell pattern table are transferred over a data communication link.

4. A digital data display system in accordance with claim 1, wherein,

said third means comprises means to calculate successive versions of the pattern of pels needed to represent a given screen cell according to components of said first level description to be represented in that cell, and wherein,

said fourth means is operative to associate the final version of said pattern of pels with said screen definition table.

5. A digital display system in accordance with claim 1, wherein

said third and fourth means have plural phases of operation for a given picture, said phases comprising

a first phase in which said third means accepts coordinates of each line passed to it and builds a character definition set for that line, and

a second phase in which the fourth means operates to modify the character set to accommodate intersections with other lines and shadings in the same picture,

whereby a character definition set for the whole picture is constructed, with redundancies in said set eliminated.

6. A method, implemented in a digital data display system, for presenting a graphical picture on an output device in which the area or screen from which the picture is to be viewed is notionally divided into a plurality of character cells each of which comprises a predetermined number of picture elements (pels), said method comprising the steps of

creating, in response to input information, a first level description of all the elements of a picture to be presented,

storing a screen definition table having an entry for each character cell of the display area,

calculating for each element of the picture, the pattern of pels in associated character cells required to display the elements, storing the calculated pattern in a table in a character cell store and associating the respective entry in the screen definition table with the required pattern in the character cell store,

determining when a particular character pel pattern has already been calculated as required for a picture and associating the respective screen definition table entries with only one copy of the particular character cell pel pattern, and

transferring the screen definition table to a screen definition buffer store and the character cell pattern table to a character cell buffer store in the display device,

whereby the contents of the screen definition buffer store and character cell buffer store control the construction of a picture presented by the display device.

7. A method in accordance with claim 6 wherein, said steps of calculating and determining comprise calculating successive versions of the pattern of pels needed to represent a given screen cell according to components of said first level description to be represented in that cell, and associating the final version of said pattern of pels with said screen definition.

8. A method in accordance with claim 6, wherein said steps of creating and calculating have plural phases of operation for a given picture, said phases comprising

a first phase in which coordinates of each line to be displayed are utilized in said calculating step to build a character definition set for that line, and

a second phase in which the calculating and determining steps are utilized to modify the character cell table to accommodate intersections with other lines and shadings in same picture,

whereby a character definition set for the whole picture in constructed, with redundancies in said set eliminated.

9. The method of claim 7, further including additional iterations of said calculating and determining steps to modify the final character set in accordance with shadings required in said picture.