Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!husc6!hao!ames!ucbcad!ucbvax!CORY.BERKELEY.EDU!dillon
From: dillon@CORY.BERKELEY.EDU (Matt Dillon)
Newsgroups: comp.sys.amiga
Subject: Re: Question about TEST:
Message-ID: <8710280010.AA05859@cory.Berkeley.EDU>
Date: Tue, 27-Oct-87 19:10:58 EST
Article-I.D.: cory.8710280010.AA05859
Posted: Tue Oct 27 19:10:58 1987
Date-Received: Fri, 30-Oct-87 06:30:31 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 50

>The "sample DOS device" Matt Dillon posted isn't re-entrant. It's serially
>reusable, but it won't allow two copies to run concurrently.
>
>Is this a problem?

	No.  Only one TEST: can run at a time with the same image.  If you
notice, I set the Task field in the device node which means DOS will not
startup a TEST: for each reference.

	Multiple Mountlist entries brings in the binary multiple times so
there is no problem there.

	If I were to write a CON like device, I would not set the Task field
in the device node and would have to be careful to make it fully reentrant.
This means no global variables except SysBase and DOSBase!!! unless they are
to be shared (i.e. follow some locking protocol).

>How *do* you remove drivers? Is it acceptable to do so?

	Good question.  I think DOS removes cached drivers under low memory
conditions.

>How much of the startup code is related to it being a driver, and how much
>is related to it being this particular driver? That is, what can I chuck out
>if I'm going to use it for VT100:? [answer: if you don't know, you ain't
>gonna be able to get it working anyway :->. right?]

	Most of the startup section is generic.... it should be obvious
by looking at it. 

>I know I can't call dos.library from a driver. How about intuition.library
>or graphics.library?

	Sure... this is just another process.  You don't want to call 
something that will go through DOS.  That is, your program can pause, but
the condition that causes it to continue should not be dependant on dos.
(i.e. a Read() call or something).

>Is it worthwhile supporting the clipboard in vt100:? Do any other programs
>than Notepad actually use the silly thing?

	The problem with the clipboard is that it is somewhat unneccesary
considering that we already have a device oriented DOS... it makes more 
sense to make the clipboard a DOS device that programs can write to without
having to do anything fancy...  Have the DOS handle standard conversions
to IFF... so you can do things like 'CLIP:IFF' and read or write raw IFF,
or something like 'CLIP:TEXT' and write standard text with the driver 
converting to IFF internally.

				-Matt