Using the Cray library to read and write COS-blocked files:

  I. Word Size
     SUN and SGI:
     Programs are compiled so that integers are 64-bit integers.

     LINUX:
     Currently, there is no way to force the GNU compiler to compile with 64-bit
     integers.  This means that you will have to either 1) explicitly declare
     the integer buffers used in the subroutine calls as INTEGER*8, or 2) you
     will have to dimension the 32-bit integer buffers twice the length that
     would be required if the integers were 64-bit.
     Example:
        INTEGER*8 IBUFFER(1000)
                          ^^^^
        CALL RDTAPE(IUNIT,MODE,NTYPE,IBUFFER,1000)
                                             ^^^^
        - OR -
        DIMENSION IBUFFER(2000)
                          ^^^^
        CALL RDTAPE(IUNIT,MODE,NTYPE,IBUFFER,1000)
                                             ^^^^

 II. How to Compile Programs

     % cf77 <filename>

     The cf77 command will link your Fortran program with the Cray I/O
     libraries.

III. Opening and Closing COS-blocked Files
     CALL CRAYOPEN(IUNIT,FILENAME,MODE,IST)
     CALL CRAYCLOSE(IUNIT)

     where:
       IUNIT    = File unit number (passed by user)
       FILENAME = Name of the file to open (passed by user)
       MODE     = 'r' or 'R' to open for reading
                  'w' or 'W' to open for writing
                  (passed by user)
       IST      = Status of the open (returned to user)
                  0 = successful
                  1 = failed

     Note about implicit open:  For read and write operations, these routines
       support implicit opens.  If your file is named 'fort.xx', you can call
       RDTAPE or WRTAPE with IUNIT=xx without having to explicitly open the file
       with a call to CRAYOPEN.

     Note about implicit close:  For write operations, these routines support
       implicit closes on the Sun only.  On the SGI, you need to call CRAYCLOSE
       explicitly or the file buffer will not be flushed when the program
       terminates.

 IV. Reading a COS-blocked File

     CALL RDTAPE(IUNIT,MODE,NTYPE,IBUFFER,LENGTH)
     CALL IOWAIT(IUNIT,IST,IWDS)

     where:
       IUNIT   = File unit number (passed by user)
       MODE    = ignored
       NTYPE   = ignored
       IBUFFER = Location to hold the next record in the file (passed by user)
       LENGTH  = Dimension of IBUFFER in 64-bit words (passed by user)
       IST     = Status of the read (returned to user)
                 0 = successful
                 1 = EOF (end of file)
                 2 = error
                 3 = EOD (end of data)
       IWDS    = Number of 64-bit words that were read (returned to user)

  V. Writing a COS-blocked File

     CALL WRTAPE(IUNIT,MODE,NTYPE,IBUFFER,LENGTH)
     CALL IOWAIT(IUNIT,IST,IWDS)

     where:
       IUNIT   = File unit number (passed by user)
       MODE    = ignored
       NTYPE   = ignored
       IBUFFER = Location holding the record to write to the file (passed by
                 user)
       LENGTH  = Number of 64-bit words to write (passed by user)
       IST     = Status of the write (returned to user)
                 0 = successful
                 2 = error
       IWDS    = Number of 64-bit words that were written (returned to user)