Error Messages and Codes 
                                  I/O Errors 

      I/O errors encountered during runtime are numbered from 100 to 149.
      If the programs are compiled in the {$I-} (error checking off) state,
      the program will continue to execute, otherwise the program will
      terminate and display the runtime error code and message.

      If you compile with the I/O checking off {$I-}, you are responsible
      for checking the status of all I/O functions with the IOresult
      function.  The value returned by IOresult will be 0 if the operation
      has been successfully completed, else it will hold one of the error
      codes below.


   #   MESSAGE                            CAUSES & REMEDIES
 ----------------------------------------------------------------------------

 100. Disk Read Error            Returned by the Read function when you
                                 attempt to read past the end of a typed
                                 file.

 101. Disk Write Error           Returned by Close, Write, WriteLn or Flush
                                 if the disk is full.

 102. File Not Assigned          Returned by Reset, ReWrite, Append, Rename,
                                 and Erase if the file variable has not been
                                 assigned a name with the Assign procedure.

 103. File Not Open              Returned by Read, Write, Seek, FilePos, Eof,
                                 BlockRead, BlockWrite, Close, FileSize, or
                                 Flush if attempted on a file that has not
                                 been opened.

 104. File Not Open For Input    Returned by Read, ReadLn, Eof, Eol, SeekEof,
                                 or SeekEol if attempted on a Text File that
                                 has not been previsously opened for input.

 105. File Not Open For Output   Returned by Write, WriteLn if used on a
                                 Text File that has not been opened.

 106. Invalid Numeric Format     Returned by Read or ReadLn when a numeric
                                 value read from a Text File does not conform
                                 to the proper numeric format.