c
c parameters:
c   blocklen is the size of the units tar works with
c   saveblocks is the number of blocks into the file saved for a second chance
c   maxrecl is the maximum length of record a text can have
c   maxblockfactor is the maximum blocking factor this program can deal with
c
      parameter blocklen = 512, saveblocks = 5, maxrecl = 512,
     -    maxblockfactor = 20

c secondary parameters calculated from those above
      parameter recblocks = 2 + maxrecl/blocklen,
     -   maxblocks = maxblockfactor + saveblocks + recblocks,
     -   maxlen = blocklen*maxblocks

c these are numbers for fortran units to be used for various files
      parameter inunit = 1, outunit = 2, listunit = 3, nameunit = 4

c
c variables:
c
c i/o control stuff
      integer*2 channel
      logical*1 tape_file

c this is the buffer records get read into
      character buffer*( maxlen ), block( maxblocks )*( blocklen )
      equivalence ( buffer, block )

c control info for the buffer
      integer*2 using, using2, curr
      logical*1 eof


      common /commonbuf/ buffer
      common /commonints/ using, using2, curr, eof, tape_file, channel