Opening a Device File

• "Device-Dependent File Characteristics" discusses those file characteristics affected by particular devices.

• "New and permanent device files" discusses the domains required by various input/output devices.

• "Opening an unlabeled magnetic tape file" shows an example of an HPFOPEN call that opens an unlabeled magnetic tape file (see example 5-5).

• "Opening a labeled magnetic tape file" shows an example of an HPFOPEN call that opens a labeled magnetic tape file (see example 5-6).

Device-dependent file characteristics

New and permanent device files

NOTE: The HPFOPEN intrinsic assumes that all files on nonshareable devices (device files) are permanent files. To maintain compatibility with MPE V/E, device files can be opened with the domain option specifying a new file, but a warning is returned in the status parameter.

• Indicate that the file resides on a device that is not in auto-recognition mode. No DATA command is required; the System Operator simply allocates the device.

• Make the file available on an auto-recognizing device, and allocate that device.

• Indicate that the file does not exist on any device; in this case, your HPFOPEN/FOPEN request is rejected.

Opening an unlabeled magnetic tape file

  procedure open_unlabeled_magnetic_tape_file;

  const
     formal_designator_option = 2;     {defines HPFOPEN itemnum 2  }
     domain_option            = 3;     {defines HPFOPEN itemnum 3  }
     access_type_option       =11;     {defines HPFOPEN itemnum 11 }
     density_option           =24;     {defines HPFOPEN itemnum 24 }
     device_class_option      =42;     {defines HPFOPEN itemnum 42 }

  type
     pac80  = packed array [1..80] of char;

  var
     tfile_num        : integer;{required HPFOPEN filenum parameter }
     status           : integer;    {returns info if err/warn occurs}

     file_name        : pac80;         {declares HPFOPEN itemnum 2  }
     permanent        : integer;       {declares HPFOPEN itemnum 3  }
     update only      : integer;       {declares HPFOPEN itemnum 11 }
     device_class     : pac80          {declares HPFOPEN itemnum 24 }
     density          : integer;       {declares HPFOPEN itemnum 42 }

  begin
     tfile_num      :=0;
     status         :=0;
     file_name      :='&tapefile&';   {delimiter is "&"             }
     permanent      :=1;              {search system file domain    }
     update_only    :=5;              {preserves existing data      }
     density        :=1600;           {select this tape density     }
     device_class   :='&tape&'; {system-configured device class name}

     HPFOPEN (tfile_num, status,
       formal_designator_option, file_name, {formaldesignator option}
       domain_option, permanent,            {domain option}
       access_type_option, update_only      {access type option}
       density_option, density,             {density option}
       device_class_option, device_class    {device class option}
       );

     if status <> 0 then handle_file_error (tfile_num, status);
  end;

Opening a labeled magnetic tape file

  procedure open_labeled_magnetic_tape_file;

  const
     formal_designator_option = 2;     {defines HPFOPEN itemnum 2  }
     domain_option            = 3;     {defines HPFOPEN itemnum 3  }
     tape_label_option        = 8;     {defines HPFOPEN itemnum 8  }
     tape_expiration_option   =31;     {defines HPFOPEN itemnum 31 }
     device_class_option      =42;     {defines HPFOPEN itemnum 42 }

  type
     pac80  = packed array [1..80] of char;

  var
     file_num         : integer; {required HPFOPEN filenum parameter}
     status           : integer;    {returns info if err/warn occurs}

     file_name        : pac80;         {declares HPFOPEN itemnum 2  }
     old              : integer;       {declares HPFOPEN itemnum 3  }
     tape_label       : pac80;         {declares HPFOPEN itemnum 8  }
     expire_date      : pac80          {declares HPFOPEN itemnum 31 }
     device_class     : pac80          {declares HPFOPEN itemnum 42 }

  begin
     file_num       :=0;
     status         :=0;
     file_name      :='&labltape&'; {delimiter is "&"               }
     old            :=3;         {equivalent to specifying permanent}
     tape_label     :='&tape01&';     {ANSI tape label              }
     expire_date    :='&05/20/87&'    {when data is no longer useful}
     device_class   :='&tape&';       {system-configured device name}

     HPFOPEN (file_num, status,
       formal_designator_option, file_name, {formaldesignator option}
       domain_option, old,                  {domain option}
       tape_label_option, tape_label,     {labeled tape label option}
       tape_expiration_option, expire_date,
                                     {labeled tape expiration option}
       device_class_option, device_class     {device class option}
       );

     if status <> 0 then handle_file_error (file_num, status);
  end;