Re: BASIC for the CBM-II/8088

scrolling and clearing can be done with the same int 10h call

Scroll up window 	AH=06h 	AL = lines to scroll (0 = clear, CH, CL, DH, 
DL are used),

BH = Background Color and Foreground color. BH = 43h, means that 
background color is red and foreground color is cyan. Refer theBIOS 
color attributes <https://en.wikipedia.org/wiki/BIOS_color_attributes>

CH = Upper row number, CL = Left column number, DH = Lower row number, 
DL = Right column number

	
Scroll down window 	AH=07h 	like above


It'll probably not be as fast as directly writing to the screen, but 
much faster than an int 10h loop

examples here:

http://www.shsu.edu/~csc_tjm/fall2000/cs272/ch7.html


On 06/07/2018 14:10, Baltissen, GJPAA (Ruud) wrote:
> Hallo allemaal,
>
>
> Update:
>
>> The next code:
>> .....
>> needs about 2 seconds to clear a screen;
> As I said before, I learn something in the process as well.
>
> I also found out that I used direct screen accesses for doing my own scrolling. Reading a character using INT 10h and writing it to the next or previous line would take even longer than 2 seconds IMHO. But having seen Michał's CBM-II in action, I knew I had something wrong. Studying some INT 10h documents I noticed some routines for scrolling. One could be even used to clear the screen according its documentation. And yes indeed, it works like a charm! It is less faster than the direct access method but better than I expected.
>
>
> Met vriendelijke groet / With kind regards, Ruud Baltissen
>
> www.Baltissen.org
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