19. Advanced File Input and Output
  This chapter describes the more advanced I/O features avail-
  able in BASIC. For more information about I/O to RMS disk
  files, see Chapter 14. The following topics are presented:

  .
        RMS I/O to ANSI magnetic tapes
  .
        Device-specific I/O to magnetic tapes (including TK50
        devices), disks, and unit record devices
  .
        I/O to mailboxes
  .
        Network I/O

  When you do not specify a file name in the OPEN state-
  ment, the I/O you perform is said to be device-specific .
  This means that read and write operations (GET and PUT
  statements) are performed directly to or from the device. For
  example:
  OPEN "MTA2:" FOR OUTPUT AS FILE #1
  OPEN "MTA1:PARTS.DAT" FOR INPUT AS FILE #2, SEQUENTIAL

  Because the file specification in the first line does not contain
  a file name, the OPEN statement opens the tape drive for
  device-specific I/O. The second line opens an ANSI-format
  tape file using RMS because a file name is part of the file
  specification.

  The following sections describe both I/O to ANSI-format
  magnetic tapes and device-specific I/O to magnetic tape, unit
  record, and disk devices.