Re: Mode 13h

["Tommi Pirinen" <tommi.pirinen@dlc.fi>]

for some reason most of the modern compiles compile this code but it doesn't
work.
and actually  faster method than y*320 is (y<<6)+(y<<8) but that isn't
necessary for modern computers they are too fast anyways.
And for some compilers it has to be unsigned char far. and color must be
unsigned char (0 - 255).
about the outportb you use. isn't 0x3C9 Palette address.  so writing
anything to that address will change the value for that palette index (which
is set via 0x3c7 I think)
correct me if I'm wrong as I'm typing this in a bit hurry and don't have
time to check the information.
--Tommi Pirinen
----- Original Message -----
From: Nick Hill <nikhilwiz@yahoo.com>
To: <gameprogrammer@gameprogrammer.com>
Sent: Wednesday, September 08, 1999 5:27 AM
Subject: Re: Mode 13h


> make a pointer to 0xA000
> unsigned char *VidMem=0xA000. This makes a pointer to tha vid. mem.
> Mode 13h is a linear buffer where 1 byte represents one pixel. u can
> plot a pixel by writing the color of tha pixel to tha particular mem.
> loc. Since the data in the vid. mem. start from (0,0) and proceeds
> along tha row, the first 320 bytes represents tha first row., u get tha
> idea. so tha formula to calc. tha byte at (x,y) on screen will be :
>
> pos=y * 320 + x;
> VidMem[pos]=color;
>
> where color is tha color of tha pixel u wanna plot. Keep it under 255,
> as Mode 13h s'portz only that much. thazz why tha data type on VidMem
> also is defined as unsigned char... so that u wont end up writing
> NEthin' oth' than 0-255. Hope this helped.
>
> Nikhil.
>
> --- Peter Peterssen <getoutnow@Hotmail.com> wrote:
> > Hello..
> >
> > Mode 13H. Wow. Then, perhaps you can tell me how the
> > heck I draw a dot on
> > the screen like X and Y ?
> >
> > I do call 0xA0000 and the use the..
> > outportb(0x3c9, red);
> > outportb(0x3c9, green);
> > outportb(0x3c9, blue);
> >
> > .. for the background layout and then ..
> >
> > b= 0;
> > pokeb(0xa0000, B,30)
> >
> > .. for the actual dot.
> >
> > This doensnt work unless i add 1 to red OR green OR
> > blue. ( I dont see the
> > dot on the screen).
> >
> > So, as you see Im totaly lost and really dont get
> > the whole thing. Do you
> > have an example how to structure something?
> >
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