Re: Setting a pixel on the screen

...And that's not right because ! stores a double word and I only want a 
word (16 bit colour).

Block 34 (icons) has !w which stores a 16 bit word to a byte address.  
That's what I need instead of 2/ 2/ !

Also, on http://www.colorforth.com/forth.html it is stated "Data are 
addressed as 32-bit words, not bytes."  I'm not fully clear on how this 
works so I need to look harder.

Jason Kemp said the following on 28/05/2008 11:27:
> Hi Ray,
>
> Thanks for all the encouragement.  I cracked it on Friday and was 
> intending to reply, but I'm trying not to touch the computer over the 
> weekends now and Monday was a bank holiday too!
>
> : pixel show black screen ffff 400 400 1024 * + 2* 1e80000 + 2/ 2/ ! 
> keyboard ;
>
> It needs a 2/ 2/ because ! multiplies the address it is given by 4.  
> This must be something to do with addressing doublewords as opposed to 
> bytes--I'm sure it's something quite obvious to most but it's taking 
> me a long time to build up a picture of what's going on here.  Are 
> addresses in colorforth stored as the count of doublewords rather than 
> a true address?
>
> Jason
>
>
>
>
> Ray St. Marie said the following on 27/05/2008 20:23:
>> rethinking my previous post to this question...
>> Hi Jason,
>> Ray here
>>
>> On Tue, May 20, 2008 at 4:41 PM, Jason Kemp 
>> <[email protected]> wrote:
>>  
>>> Good evening all,
>>>
>>> I have been attempting to set a pixel on the screen to white.  
>>> Please show
>>> me what I am doing wrong:
>>>
>>> : ohno show black screen ffff 400 400 1024 * + 2* 1e80000 + ! 
>>> keyboard ;>
>>> Only the ffff and the 1e80000 are in hex.  The screen is 1024x768, 
>>> 16-bit,
>>> VESA 117h.
>>>
>>> Thanks,
>>> Jason
>>>
>>>     
>>
>> Jason, have you tried the word color after ffff, to set the color, as 
>> in...
>>
>> : ohno show black screen ffff COLOR 400 400 1024 * + 2* 1e80000 + ! 
>> keyboard ;
>>
>> I happened to be looking in an old source and reading the word SWITCH.
>> In the top of the word we see an example of writeing to AGP before
>> switching to keyboard.
>>
>> Karig has a nice look at it :
>>
>> http://www.karig.net/os/cf/g.htm
>>
>> Halfway down the page. All of the rest of that page are examples of
>> 'emit'ing pixels to the page.
>>
>> Good luck with this, Jason. Please keep me in the loop, your
>> experiments, as I'd like to try them out as well. :-)
>>
>> All the best,
>> Ray
>>
>>   
>
>
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