before i begin: 1) i don't care about portability. 2) i don't care about compatibility.
with that out of the way, my problem. i need to hold bitmap data in specific areas of memory. basically i want to control where my bitmap data is held. to skip the need to create BITMAP structures i chose to use a pre-created BITMAP and hack it on-the-fly whenever i wanted to do a bitmap operation, by setting the width, height, and *dat pointer. it doesn't seem to work. how can i do this successfully? please let it not be the line pointers! (i was once told that line pointers don't matter in memory bitmaps...)

Actually, it's:

bmp = create_bitmap_ex(bmp_bpp, bmp_w, bmp_h);
free(bmp->dat);
bmp->dat = my_bitmap_data;
for(i = 0; i < bmp->h;++i)
   bmp->line<i> = bmp->dat + bmp->w*(bmp_bpp+7)/8*i;

If the bitmap structure has a pitch variable, you could use this:
bmp->line<i> = bmp->dat + bmp->pitch*i;</code>

what is the pitch variable and why would some bitmaps have it and not others?