Path: utzoo!attcan!uunet!husc6!linus!mbunix!jcmorris
From: jcmorris@mitre-bedford.ARPA (Joseph C. Morris)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Disk inserted???
Summary: It can be done
Keywords: notready diskette
Message-ID: <40872@linus.UUCP>
Date: 12 Oct 88 21:50:08 GMT
References: <55969UH2@PSUVM>
Sender: news@linus.UUCP
Reply-To: jcmorris@mbunix (Morris)
Distribution: na
Organization: The MITRE Corporation, McLean, VA.
Lines: 42

In article <55969UH2@PSUVM> UH2@PSUVM.BITNET (Lee Sailer) writes:
<Will someone suggest a way to test for the absence of a floppy from
<a BAT file that doesn't generate the Abort, Retry, Ignore message.

I've had good luck with all flavors of drives using a test program
built around the following code fragment:


;
        mov     al,pspf1dr              ; get the disk number (1=a:, 2=b:, etc)
        sub     al,1                    ; change to zero-base
        mov     cx,1                    ; read one sector
        sub     dx,dx                   ; make it sector zero
        mov     bx,OFFSET buffer        ; ds:bx -> input buffer
        int     025h                    ; absolute disk read
        jc      readerr                 ; trouble
        jmp     ready                   ; it worked, so it's ready
readerr:
        cmp     al,002h                 ; drive not ready?
        jne     error
        mov     al,1                    ; report 'drive not ready'
        jmp     cleanup
;
error:
        mov     al,2                    ; report 'drive in trouble'
        jmp     cleanup
;
ready:
        sub     al,al                   ; report 'drive ready and able'
cleanup:
        popf                            ; get last piece off the stack
;

It uses the absolute read DOS call to try to read a sector; DOS returns
an unambiguous OK, NOT-READY, or BROKEN response.  If you use it, watch
out for the stack: the function POPs one fewer words than it PUSHes.
(This is documented by IBM.)

If anyone really needs them I've got both stand-alone and C-callable
versions of the test.  The code works with both PC's and AT's.

Joe Morris