Re: Curiousity: pragma No_Run_Time for Gnat

["chris.danx" <chris.danx@ntlworld.com>]

> But note that for OS execution it would be acceptable to depend on the
> BIOS (at least early on the startup process); after all the BIOS is there
> and it is running before the OS.  *** But it is not acceptable at all for
> execution to depend on another OS. ***
>
> In fact, I have been thinking in terms of a MIOS (Minimal Input/Output
> System) package providing access to the "minimal system" I have suggested
> before (Ada_OS talk) as a starting target (floppy, keyboard, screen): MIOS
> would probably be implemented with BIOS services: hence, in part, the
> tribute in its name.

Note: if you want a pmode OS for the x86+ this could only work via v86 mode
or only in the very early stages of bootup (which GRUB might be good for).
Using BIOS via v86 would be slow and OS developers only do this for vesa
(because graphics cards -- in particular those with nVidia chipsets -- don't
release the prog. specs for their cards).  However for initial start up such
a system would be good but you may need a 16bit compiler for real mode
stuff.

Keyboard handlers for pmode seem to be easy enough, so too does the screen.
In fact programming the screen (for text, graphics programming is more
complex) is really easy.  You write to address 0xb8000 in
attribute/character pairs for colour memory or something (don't quote me on
that) in pmode.


> BTW, what is GRUB?  And where is GNORT?

GRUB is a bootloader for OSes, in particular it can boot multiple OS from a
menu with a multiboot compliant header, *I think* (but it's supposed to boot
almost anything).  GNORT is a some kind of GNAT variant provided by ACT,
which seems to be have discontinued and either integrated into or changed
it's name to GNAT Pro Bare Board.