TOPEN(3F)																 TOPEN(3F)

NAME

       topen, tclose, tread, twrite, trewin, tskipf, tstate - f77 tape I/O

SYNOPSIS

       integer function topen (tlu, devnam, label)
       integer tlu
       character*(*) devnam
       logical label

       integer function tclose (tlu)
       integer tlu

       integer function tread (tlu, buffer)
       integer tlu
       character*(*) buffer

       integer function twrite (tlu, buffer)
       integer tlu
       character*(*) buffer

       integer function trewin (tlu)
       integer tlu

       integer function tskipf (tlu, nfiles, nrecs)
       integer tlu, nfiles, nrecs

       integer function tstate (tlu, fileno, recno, errf, eoff, eotf, tcsr)
       integer tlu, fileno, recno, tcsr
       logical errf, eoff, eotf

DESCRIPTION

       These functions provide a simple interface between f77 and magnetic tape devices.  A ``tape logical unit'', tlu, is ``topen''ed in much the
       same way as a normal f77 logical unit is ``open''ed.  All other operations are performed via the tlu.  The tlu has no relationship  at  all
       to any normal f77 logical unit.

       Topen  associates  a device name with a tlu.  Tlu must be in the range 0 to 3.  The logical argument label should indicate whether the tape
       includes a tape label.  This is used by trewin below.  Topen does not move the tape.  The normal returned value is 0.  If the value of  the
       function is negative, an error has occured.  See perror(3F) for details.

       Tclose closes the tape device channel and removes its association with tlu.  The normal returned value is 0.  A negative value indicates an
       error.

       Tread reads the next physical record from tape to buffer.  Buffer must be of type character.  The size of buffer should be large enough	to
       hold  the largest physical record to be read.  The actual number of bytes read will be returned as the value of the function.  If the value
       is 0, the end-of-file has been detected.  A negative value indicates an error.

       Twrite writes a physical record to tape from buffer.  The physical record length will be the size of buffer.  Buffer must be of type  char-
       acter.  The number of bytes written will be returned.  A value of 0 or negative indicates an error.

       Trewin rewinds the tape associated with tlu to the beginning of the first data file.  If the tape is a labelled tape (see topen above) then
       the label is skipped over after rewinding.  The normal returned value is 0.  A negative value indicates an error.

       Tskipf allows the user to skip over files and/or records.  First, nfiles end-of-file marks are skipped. If the current file is at EOF, this
       counts  as 1 file to skip.  (Note: This is the way to reset the EOF status for a tlu.)  Next, nrecs physical records are skipped over.  The
       normal returned value is 0.  A negative value indicates an error.

       Finally, tstate allows the user to determine the logical state of the tape I/O channel and to see the tape drive control  status  register.
       The  values  of fileno and recno will be returned and indicate the current file and record number.  The logical values errf, eoff, and eotf
       indicate an error has occurred, the current file is at EOF, or the tape has reached logical end-of-tape.  End-of-tape (EOT) is indicated by
       an  empty  file, often referred to as a double EOF mark.  It is not allowed to read past EOT although it is allowed to write.  The value of
       tcsr will reflect the tape drive control status register.  See ht(4) for details.

FILES

       /usr/lib/libU77.a

SEE ALSO

       ht(4), perror(3F), rewind(1)

4.2 Berkeley Distribution					   May 15, 1985 							 TOPEN(3F)