Turbo Pascal Run-time I/O Errors

  The Turbo Pascal manual lists a set of I/O run-time errors.  These
errors are those reported by Turbo Pascal when I/O error checking is on,
{$I+}.  In many cases, however the user may turn I/O error checking off
( {$I-} ) to prevent fatal runtime errors.  The most common time this is
done is when opening files.  An error at this time can be determined by
calling the standard function IORESULT.  If IORESULT is 0, then the I/O
operation was successful.

  In a conversation with one of the support people at Borland, I found that
the I/O errors listed in the manual differ from the numbers that the IORESULT
function return.  He provided me with a list of the IORESULT values for
various I/O errors.  I have not verified them, and there are a couple of
ambiguities, but they may be of some interest.

I/O Error #     IORESULT value        Error Message

   01                 2               File does not exist
   02                 5               File not open for input
   03                 6               File not open for output
   10                 9               Error in numeric format
   20                16               Operation not allowed on logical device
   21                17               Not allowed in direct mode
   90               144 or 1          Record length mismatch
   99                10               Unexpected end-of-file
   F0                13 or 8          Disk write error
   F1                 3               Directory is full
    ?                22               Assign to std files not allowed