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From: cc100jr@gitpyr.UUCP (Joel M. Rives)
Newsgroups: net.micro.pc,net.lang.pascal,net.wanted.sources
Subject: Re: Device checking in Turbo
Message-ID: <1474@gitpyr.UUCP>
Date: Wed, 26-Feb-86 12:40:01 EST
Article-I.D.: gitpyr.1474
Posted: Wed Feb 26 12:40:01 1986
Date-Received: Fri, 28-Feb-86 06:58:52 EST
References: <198@dcc1.UUCP>
Reply-To: cc100jr@gitpyr.UUCP (Joel M. Rives)
Distribution: net
Organization: Office of Computing Services, Georgia Tech
Lines: 82
Xref: watmath net.micro.pc:7159 net.lang.pascal:481 net.wanted.sources:1944

In article <198@dcc1.UUCP> bingaman@dcc1.UUCP (George C. Bingaman) writes:
>
>    Can anyone tell me how I can get version 2.0 of Turbo Pascal running under
>MS/PC-DOS to check the status of a device?  I would like to verify that the
>printer is online, and that the drive is ready before doing I/O.  I would also
>like to have the program check to see what drive it is being run from.
>    I have looked thru Borland's reference manual, but if the info is there I'm
>missing it.  Any help would be greatly appreciated.
>
--------------------------------------------------------------------------------

I recommend that you re-read section 14.8 in the Version 2.0 Reference Manual.
This section deals with the function IOresult. By setting {$I-} as a compiler
directive, you can do your own I/O error trapping. Experiment a little. It can't
hurt and you may learn a lot. 
One suggestion for checking which drive the program is running from is as   
follows:

   Assume that the name of the program you are running is called "myprog.com".

const
	 MaxDrive = { the greatest reference letter for a disk drive for
		       your system }
type
	 drives   = '@'..MaxDrive; { @ = no drive or nil drive }


{$I-}
function disk_drive: drives;
  var
	 exists     : boolean;
	 drive      : drives;
	 test	    : text;
	 path       : string[20];
begin
  assign(test,'dummy.tst');
  rewrite(test);
  writeln(test,'This is a test file');
  close(test);
  exists := false;
  drive := '@'; 
  while (not exists) and (drive < MaxDrive) do
  begin
    drive := drives(ord(drive) + 1);
    path := drive + ':' + 'dummy.tst';  
    assign(test,path);
    exists := IOresult = 0;
    close(test);
  end;
  erase(test);
  if exists then 
    disk_drive := drive 
  else
    disk_drive := '@';
end; { disk_drive }
{$I+}

This function could be called (in this example) as follows:

var
       current  : drives;
begin
    .
    .
    .
  current := disk_drive;
    .
    .
    .
end.

The variable "current" should then contain the letter of the drive which
the program is currently working from.

			    -Joel Rives

Joel Rives
Georgia Insitute of Technology, Atlanta Georgia, 30332
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