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From: phys169@csc.canterbury.ac.nz
Newsgroups: comp.lang.pascal
Subject: Re: Help in Printer Status!
Message-ID: <1991Jun24.163223.1178@csc.canterbury.ac.nz>
Date: 24 Jun 91 04:32:23 GMT
References: <1991Jun22.163830.21689@cs.mcgill.ca>
Organization: University of Canterbury, Christchurch, New Zealand
Lines: 31

In article <1991Jun22.163830.21689@cs.mcgill.ca>, dara@cs.mcgill.ca (Dara UNG) writes:
>    I've tried the following code suggested by Tom Swan, "Mastering Turbo
>    Pascal 5.5", but the output from PrintStatus always is 255
>    regardless of the ON/OFF state of printer!
> 
Try...
    var   PrintStatus : byte;
          LptPortAddr : array[1..4] of word absolute 0:$408;
    begin
 	 PrintStatus := Port [LprPortAddr[1]];
 	 writeln (PrintStatus);
    end;
 
The idea is to find the actual port addresses from the table BIOS creates
during power-on self-testing. Otherwise teh port address for LPT1 depends
on such factors as the type of vidoe display you have.

An even better idea is to use interrupt $17 (with AH=2) or possibly MsDos call
$44, to allow for such things as printer redirection. So you could declare...

 const LPT1 = 0; LPT2 = 1; LPT3 = 2; LPT4 = 3;

 function PrinterStatus(WhichPrinter : word) : byte; 
 inline($B4/$02/       { mov ah,2  }
        $5A/           { pop dx    }
        $CD/$17/       { int 17h   }
        $8A/$C4);      { mov al,ah }

Hope this helps,
Mark Aitchison, Physics, University of Canterbury, New Zealand.
[insert favourite quote from BlackAdder/Goodies/Spike Milligoon/Penfold here]