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From: jrv@siemens.UUCP
Newsgroups: net.micro.pc
Subject: Re: Device checking in Turbo
Message-ID: <23900007@siemens.UUCP>
Date: Thu, 27-Feb-86 09:50:00 EST
Article-I.D.: siemens.23900007
Posted: Thu Feb 27 09:50:00 1986
Date-Received: Sat, 1-Mar-86 03:13:57 EST
References: <198@dcc1.UUCP>
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Nf-ID: #R:dcc1:-19800:siemens:23900007:000:1119
Nf-From: siemens!jrv    Feb 27 09:50:00 1986




For testing the status of a device, MS-DOS provides function 44h -
I/O control for Devices.

To check for printer status set the registers before the function
call as follows:
	ah = 44h	I/O Control for Devices
	al = 07h	Get output status
	bx = 04h	Standard printer file handle

You'll need to find the exact Turbo-Pascal syntax to do this.
On return from the function call Al = 0ffh if the printer is ready
and 00 if it is not. (I just tested this to make sure.) If you want
to test other than the standard printer then you will have to open
that device first to get a file handle for it to place in the BX register.

For testing disk drives I know of no way other than trying to read/write
to them. You then run into the problem of getting the MS-DOS error if
the disk drive is not ready (i.e. an open floppy door). To trap this you
have to substitute for the Critical Error Handler at Interrupt 24h.
However, you still have to wait for the floppy drive to power up and find
that it is not ready.  

Has anyone found a better way to test for disk ready status??

Jim Vallino
{allegra,inhp4}!princeton!siemens!jrv