Re: Linux in Forth?

Op Tue, 19 Jul 2005 11:52:35 GMT schreef David Given:

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> Paul E. Bennett wrote:
> [...]
>> It seems you may have read it with a different slant to my reading of it.
>> I thought that there was a reasonable case for modularity and abstraction
>> but with a note to keep both aspects appropriate to the natural stucture
>> of the system.
>
> Hrm.
>
> Let me expand: on pages 92..94, there's a discussion of data hiding. As an
> example, Leo uses the PC BIOS text display interface as an example; it
> provides a number of entry points for doing various things on the console.
> He then points out that there is no entry point for displaying a string of
> text, which means that the only way to do it is to repeatedly call the
> display-character routine: this is slow.
>
> He then says that the correct thing to do is to provide a word that returns
> the address of the video memory, which allows the API to be extended by the
> user.

In the second print (1994) Leo warns the reader on page 80 that a hardware
revision might not survive that kind of code. But even in 2005 a DOS
programmer can store characters directly in the screen buffer.

> But this is just plain *wrong* --- by exposing the address of the video
> memory, you have to make public the format of the framebuffer, which means
> you can't change your implementation without breaking your API.

It's of course wrong, but DOS programmers always had success with it. There
was no API.

Coos
--
CHForth, 16 bit DOS applications
http://home.hccnet.nl/j.j.haak/forth.html
.

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