Computer graphics processing and selective visual display system – Display peripheral interface input device – Light pen for fluid matrix display panel
Patent
1995-12-18
1998-03-10
Saras, Steven
Computer graphics processing and selective visual display system
Display peripheral interface input device
Light pen for fluid matrix display panel
345141, 345192, G09G 522
Patent
active
057266808
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a procedure for the presentation of text in a CGA-graphic mode on a screen of a personal computer, which on one hand shows a processor and a memory allocated to it, in which binary patterns of the text to be presented are stored, and on the other hand a video-card connected with such processor via an external bus. Such video-card has a video-memory whose memory contents can be presented on the video-screen, whereas on demand of a text character, first of all its binary pattern is called from the memory, this is supplemented by character-colour (front colour) and background-colour stored as a pixel-pattern in the video-memory and displayed on the screen.
2. Description of the Prior Art
Part of the CGA graphic-modes are the 320 times 200 bit-mode, carrying the BIOS-Code 4 and, with which four colours can be presented on the screen at the same time, some restrictions given, the 620 times 200 bit-mode, carrying the BIOS-Code 6 and enabling a presentation in two colours and finally a variant of the first-mentioned graphic-mode, carrying the mode-code 5 in the BIOS-nomenclature and in which the colour-signal is suppressed, by that producing various shades of grey. These graphic-modes are used and picked-up relatively seldom by modern software programs, but are principally supported by operating systems, because some, i.e. older programs have to resort to these modes necessarily. Full compatibility of a personal computer is only reached when the mentioned modes 4,5 and 6 are also supported.
When displaying graphic presentations, the application program has to write the two-bit value for each pixel directly into the video-memory. When presenting text, however, a special way is chosen and BIOS-functions are provided which will make it easier for the application-programmer to present text, so that the program will not have to create each text character, pixel by pixel, in each case. At least one setting of finished binary patterns are stored in one memory, with which a setting of standard text characters can be produced. To be able to present a text character, the application program will only have to message the ASCII-value of the text character to be presented to the BIOS-program, which will then provide the respective pixel-information.
The procedure of the above mentioned kind is known from the European patent 71 744. The binary pattern of a character to be presented is present in such a way that for each subsequent pixel appearing on the screen only one bit is used. The bits are then doubled, after that the colour or shades of grey attributes etc. are added. After that, this information, meaning two bits per pixel is transferred via the external bus to the video-card.
When displaying text the pixels of a text character to be presented are produced on the screen in a chosen foreground colour. The environment around these mentioned pixels is reproduced in a chosen background colour. I.e. the foreground colour is yellow, the background colour is blue. For the simplification of the description two different shades of grey are named as foreground colour and background colour, too.
The procedure of the above mentioned kind is known from the European patent 71 744. The binary pattern of a character to be presented is stored in a one-bit per pixel form. For each pixel addressed to on the screen only one bit is used.
With the procedure known these bits are first doubled, then the colour attributes are added. The information present in such a way, meaning two bits per pixel, is transferred to the video-card via the external bus and stored in the video memory.
With this procedure all two-bit information, meaning a value of one pixel in each case, are written into the video-memory, independent from whether the actual pixel-presentation is modified (foreground colour) or not (background colour). This results in the transfer of a fair amount of information per time via the external bus.
It is the object of the invention to improve and speed up th
REFERENCES:
patent: 5208908 (1993-05-01), Harrison et al.
patent: 5404445 (1995-04-01), Matsumoto
patent: 5502808 (1996-03-01), Goddard et al.
IBM Technical Disclosure Bulletin, Video Compatibility Feature, V. 28, No. 6, Nov. 1985, pp. 2615-2620.
Bauer Wulf
Paley Greg
Lezdey John
Saras Steven
Vobis Microcomputer AG
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