Re: Environmental Variables


On 8 Aug 2005, Ali wrote:

> ALI Wrote:
>
> >You have to justify this! DOS is in fact a shell running from
> explorer.exe's context if you have opened it from start menu or while
> typing 'cmd' in run dialog box;-) Though it is not as much advance
> as compare to linux or unix shells. BUT it is shell. See the shell
> defination for desktop Operating Systems.
>
> Ted Wrote:
> >NT does not have an underlying DOS - that is, it does not run as a DOS
> application as Win9x does. It has a DOS emulator, but it is not
> complete and unlike real DOS, the 'DOS' window is in fact a Windows
> application.
>
>
> Isn't the same thing that "DOS is in fact a shell running from
> explorer.exe's context if you have opened it from start menu or while
> typing 'cmd' in run dialog box" == "the 'DOS' window is in fact a
> Windows
> application"

DOS is not a shell. It is an operating system with a specific API.
Windows 3.x runs on top of DOS so any shell has the DOS API available.
Much of Windows 95 and 98 is based on DOS so the same API is available
there. COMMAND.COM is a shell that uses that API for system calls and
Windows versions can also use system calls to handle long filenames. 4DOS
is a shell that uses that API (and the additional system functions in
Windows that provide long filenames). bash is a shell (and I believe that
shell has been ported to DOS and/or Windows).

Versions of Windows based on Windows NT do not use the DOS API.
CMD.EXE is a shell that can *emulate* most of the DOS API but not
all of it faithfully.

Programs running on DOS or on DOS-based versions of Windows also have
virtually all of the BIOS functions available. That is not so with
Windows NT systems. Try writing a script to read and/or write your
hard disk Master Boot Record with DEBUG.EXE and see how well it works
(or, rather, doesn't work) on a Windows NT system.

>
>
> So where is the difference? i didn't said any thing about win 9.x or NT
> pro systems?
> I very well understand difference between these families and how VXDs
> were replaced by NT kernel mode drivers , today known WDM [windows
> driver model] drivers.
> In fact VXDs were for NT pre systems [w3.1 , w95 , w98]. And WDM are
> targeted for NT pro systems;-) [ NT release of workstations ,w2K so on
> and so forth ].
> We will soon see WDF drivers [Windows Driver Framework] which is in
> beta at the moment.
>
> NOW i'm repeating my statement again "DOS is shell. Though it is not as

No. COMMAND.COM or 4DOS or CMD.EXE are shells. Windows 3.x and Tempest
and Deskview were graphical shells.

> much advance
> as compare to linux or unix shells. BUT it is a shell. See the shell

Linux or Unix are Operating systems. sh or bash or csh are shells that
can run on Linus or Unix.

> defination for desktop Operating Systems.
> No matter how it was implemented on NT pre or NT pro systems, but it is
> a shell;-)

No.

--
Windows is *not* a "Toy OS". A screenshot of my current desktop:
<http://www.chebucto.ns.ca/~af380/MyDeskTop-Jun-22-2005.gif> Want a desktop
like that? (change ".zip" to ".gif" or "-files.gif" to see zip contents):
<http://www.chebucto.ns.ca/~af380/EtchASketch.zip>

.

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