From: rommel@Informatik.TU-Muenchen.DE (Kai-Uwe Rommel)
Subject: Re: Windows 3.1 an "operating system"?
Organization: Technische Universitaet Muenchen, Germany
Date: Mon, 23 Nov 1992 12:27:36 GMT

In article <1992Nov21.233133.22965@muddcs.claremont.edu> tlilley@jarthur.claremont.edu (Thomas (Ted) Lilley) writes:
>From "Computer Operating Systems for micros, minis and mainframes", by
>David Barron, Professor of Computer Studies, University of Southampton:
>
>	"CP/M is made up of three modules, called BDOS, BIOS and CCP.
>
>	(1) BDOS, the Basic Disc Operating System, .....
>
>	(2) CCP (Command Control Processor) is responsible for the user
>	    interface...
>
>	(3) BIOS (Basic Input Output System) is the only part of CP/M that is
>	hardware dependent.  It implements the system calls of BDOS, mapping
>	the hardware-independent interface on to the actual hardware devices
>	in use. Each microcomputer manufacturer supporting CP/M provides a
>	BIOS customized to his particular hardware."
>(p. 26-27)
>
>	"In CP/M all the hardware-dependent code is gathered into BIOS, and
>	BDOS presents a hardware-independent interface to the user."
>(p. 93)
>
>
>Now, obviously, CP/M != DOS.  The above quotes do not prove that the BIOS is
>part of DOS.  However, all arguments that the BIOS *can't* be part of
>DOS because the  BIOS is firmware, or part of the architecture, are wrong,
>else the BIOS could not have been part of CP/M.

BIOS != BIOS. Do I need to say more?

The BIOS you see as part of CP/M is integral part of CP/M, kind of
packed set of device drivers for the hardware CP/M is tobe run on. It is
delivered by the software vendor who is providing C/PM for the
particular machne, not necessarily the hardware vendor.

This is about the same like the combined set of kernel device drivers of
a Unix implementation for a machine or like the base device drivers of
OS/2.

The point is, that the BIOS of a PC used by Windows is something
different. It is not provided by the software vendor (Microsoft) and
the use of it by the software (Windows) must thus be SO generic that it
runs on top of it without ever being tested before (only some machines
are tested by MS). 

This has the implication, that only the most commonly provided services
in it can be used reliably. Also, it represents a bottleneck for
Windows because it was NEVER written with a multitasking protected
memory operating system as which MS is picturing Windows. The
computer's ressources cannot be used fully through the PC BIOS because
it simply isn't capable of that. MS works around this in most areas
except for disk/file systems access. i know there is a 32-bit file
access driver, but there is no generic scheme to link in a "disk device
driver" like in Unix or OS/2. Also, by going through DOS for the file
system management and then going back into Windows's 32-bit disk driver
most of the advantage of the 32-bit driver is lost, because the DOS
serializes all access attempts.

Kai Uwe Rommel

/* Kai Uwe Rommel --- rommel@informatik.tu-muenchen.de */

DOS ... is still a real mode only non-reentrant interrupt
handler, and always will be.                -Russell Williams

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