"CP/M compatible" vs. "MS-DOS Compatible" machines?

Roy J. Tellason rtellason at verizon.net
Tue Feb 5 01:20:29 CST 2008

On Monday 04 February 2008 14:48, Chuck Guzis wrote:
> I wanted to add a "put that diskette back" alarm to my CP/M
> implementation when there were files opened for writing


> (one needn't even turn on the drive motor--just periodically sample the
> write-protect status; a diskette being inserted or removed will toggle it a
> couple of times).

I had some drives that also had a switch that would go active when the door 
was opened,  I think originally intended for the Wang PC or similar,  they're 
FH 5.25" but worked as well as anything else with the Bigboard II when I had 
them hooked up to it.

> I'd already done it for DX-85M

What's that?

> and it reduced our diskette file corruption problems to nearly zero. 
> That "R/O error" diagnostic from CP/M was unreliable at best and nearly
> useless even when it worked.


> It was then that I discovered that CP/M made no attempt to track open
> files and indeed, the behavior of many programs depended on this.

It wasn't really much of an OS,  compared to a lot of what else was out there.

Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin

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