Legacy apps in Windows/OS X was Re: Old MS-DOS & Win Software

[Chuck Guzis]

On 12/7/2005 at 6:32 PM Teo Zenios wrote:

>I don't see the point of having so much legacy support in newer OS
versions
>(it is more complicated and has more code to create bugs). If there is a
>need for such things then some company will develop a means of using your
>older software via an emulator. Besides what is so hard about keeping a
>legacy system in the house if you really need to run a 10 year old app on
>occasion? OS developers should concentrate on making their OS stable and
>reliable plus having good APIs, not in programming emulators and other
>add-ons.

...and that's the point of Vista not having 16-bit support, I suppose.
NT/2K/XP doesn't emulate 16 bit at the instruction level, it switches the
processor to protected 16-bit operation and deals with interrupt vector
mapping and other nonsense.  Heck, 16 bit doesn't run as fast as 32-bit or
64-bit mode on the X86 CPUs anyway--I've wondered for a long time why PCs
still boot up in it.

In an ironic sense of justice, MS has had to support most of the design
mistakes it made in Windows 3.0 and MS-DOS by providing support for old
applications.  Intel has had to live with the instruction set of the 8080
all these years, only being allowed to extend it, but keeping things like
the DAA instruction intact and supporting a bunch of do-nothing
instructions like MOV DL,DL.       

Consider on Windows XP that you can still run the following code:

	mov	cl,9
	mov	dx,offset HWMes
	call	5
	mov	cl,0
	call	5

HWmes	db	13,10,"Hello World$"

Now, is that crufty or what?

Maybe it's time to move on.  We can always emulate what we need to.

Cheers,
Chuck