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User's Choice Windows CD (CMS Software)(1993).iso
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1992-02-17
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Look MA, All The Neat Things I Could Do, if Only I Were a VxD!
1 EDOS, a DOS extender for Windows Enhanced Mode
EDOS is a powerful device driver program that extends the DOS
environment to make DOS, Windows aware whenever DOS is being run
from inside Windows. It's primary features include new command
line commands and the ability to disable DOS commands. New
commands provide technical information about the state of the DOS
box and the state of Windows. Also, the ability to change PIF
settings originally changeable only with the PIF editor. Other
features include a hot key for exiting from a DOS Box, ability to
view the clipboard and an alarm that returns you to the DOS Box
where the alarm was originally created. Commands to start and
stop high resolution timers for performance timing are also
included.
EDOS is a VxD, a special class of Windows Device Driver. VxD's
form the very foundation of Windows Enhanced Mode. The core VxD
code resides in the WIN386.EXE file. This file consists of many
smaller pieces of code copied together to form an integrated set
of VxDs(the default system in 386 mode). Each VxD component can
be replaced in it's entirety, or one internal function at a time.
This replaceability and substitutability provides tremendous
flexibility. Windows standard/286 mode is not built this way and
lacks the flexibility, inherent therein. 286 mode is difficult to
modify, add to or replace. As a consequence, it is likely to
receive little future development work, inside or outside
Microsoft.
EDOS uses so-called "undocumented DOS" function calls, hooking of
protected mode/real mode interrupt vectors and service functions
provided by other VxDs. EDOS employs VxD services for managing
memory, scheduling, individual device and system control,
keyboard, calling DOS & BIOS services, timing, initialization
information and message displaying. In short, at least one or
more functions from every major group of VxD support routines.
A VxD runs at ring 0, the most privileged mode of the
microprocessor. Because of this EDOS has access to the most basic
parts of the Windows core. In tandem with a Windows Dynamic Link
Library, a VxD like EDOS can be built to do almost anything,
although at the present time no custom DLL is provided with EDOS.
Even though the present version 2.00a is reasonably impressive,
it is very crude compared to what could be done with more time
and effort. VxD's offer great opportunities to enhance and extend
Windows and it's components.
2 Features
EDOS features are provided by 5 groups of commands.
Control, Performance Timing, Information, Scheduling,
Miscellaneous.
Control Performance Timing Information Scheduling Misc.
ALT-F4 BOXTIME STATUS/EDOS PRIB ALARM
BOXSWITCH SYSTIME EMS PRIF
XMS BACKGROUND
PIF EXCLUSIVE
MEM SLICE
VER
CLIPBOARD
3 Overview of Feature Groups
EDOS functions & commands can be combined in a multitude of ways
to enhance the way in which you use a DOS session in Windows.
Several features are built in and simply make life easier. The
ALF-F4 exit feature is one of these. Once you become accustomed
to it, you'll never want to be without it. The other most
noticeable feature is the pif file name and edos version number
displayed at DOS session start-up. This combined with the ability
to define a batch file to be run at every DOS session start-up
means that you have almost unlimited flexibility to customise DOS
sessions in general and any session specifically.
The DOSSTART.BAT file executed at DOS session start-up is located
by Windows starting with the current directory. If not found,
then in the WINDIR directory, if not there then the PATH. If not
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found by any of these routes then a "Bad command" message will be
generated. Because of this step by step search method, you may
have numerous DOSSTART batch files. The first one found is the
one executed. By proper organization, you can cause the intended
batch file to be found, using the "properties/working directory"
option on the system menu button.
Once you have the intended batch file executing with an ICON, you
can customize to your hearts content. Any regular DOS command may
be executed, as well as all EDOS commands. With all this power at
your disposal, you may never find all the ways to combine these
commands.
A few suggestions. If you use a "CLS" first, the screen will be
cleared to a prompt. You can then issue whatever commands you
want to create the entry screen of your choice. By "TYPE" ing a
file to the screen, that says "Windows DOS Session", you will
have a highly visible indicator that Windows is running. In
short, you can execute any internal or external command or
program that you want.
Outside of setting up the screen, the most likely thing you will
want to do is add memory or change the scheduling system. Since
you can set the scheduling options from a batch file it is no
longer necessary to have a multitude of PIF files for every
situation.
The two control commands in EDOS are essentially hot key
functions. ALT-F4 pushes "exit" + enter into the keyboard buffer
which causes DOS to exit back to Windows.
BOXSWITCH controls the ability to switch out of a DOS Box and
back into Windows.
The two performance timers
The information services are the most detailed and complex of
EDOS's functionality.
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4 EDOS code consists of 4 major components.
Initialization: EDOS device initialization, hooking vectors and
services, installing hot keys.
Processing hooked interrupts, service calls and hot keys.
Parsing and analyzing command lines.
Servicing a supported command.
A discussion of each of the 4 code sections(above), emphasizing
the GENERAL principles involved ie. hooking service calls.
Ability to CONTROL Windows, Ala the ALARM command.
5 Using EDOS
A beginners perspective
A programmers testing tool
6 Weaknesses and limitations
Bugs in Windows.
Bugs in DOS.
Limitations of Windows and DOS.
Copyright 1991, Michael P. Maurice
503-694-5267
CIS 71171,47
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Contents
1 EDOS, a DOS extender for Windows Enhanced
Mode . . . . . . . . . . . . . . . . . . . . . 1
2 Features . . . . . . . . . . . . . . . . . . . 2
3 Overview of Feature Groups . . . . . . . . . . 2
4 EDOS code consists of 4 major components. . . . 4
5 Using EDOS . . . . . . . . . . . . . . . . . . 4
6 Weaknesses and limitations . . . . . . . . . . 4
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