INF: CGA Graphics Modes Support Only One Video Page

ID Number: Q70669

5.10 6.00 6.00a 6.00ax 7.00

MS-DOS

Summary:

In Microsoft C versions 5.0, 5.1, 6.0, 6.0a, 6.0ax, and 7.0, the

functions _setactivepage() and _setvisualpage() from GRAPHICS.LIB can

be used to change which portion of the video memory is being used.

These two functions can be used in both text and graphics video modes.

However, in a CGA graphics mode you are limited to one video page

because the design of the original CGA adapter supports only one page

in graphics mode.

This holds true even if your system has a newer graphics adapter, such

as an EGA or VGA, which contains more video memory. Calling the

function _getvideoconfig() correctly indicates that only one video

page is available when set to any of the CGA graphics modes, because

emulating a CGA graphics mode includes the 16K limit to video memory.

Additional reference words: 5.00 5.10 6.00 6.00a 6.00ax 7.00