[文件读写] Fortran runtime error: End of file 新手报错求助！

      parameter (lx=34,ly=30,nt=1776,nt1=25)
      REAL T(lx,ly)
      REAL T0(ly,lx),DT(lx,ly)

      OPEN(UNIT=77,FILE='../data/sst/sstasm_1856-2003',
     +     form='unformatted')
      OPEN(UNIT=78,FILE='t.out',
     +     form='unformatted')
      OPEN(UNIT=79,FILE='ldeo5_1856-2003',
     +     form = 'unformatted')
      OPEN(UNIT=80,FILE='mod_ssta_nino34.dat')
      OPEN(UNIT=81,FILE='obs_ssta_nino34.dat')
      open(unit=82,file='ta_nino34.dat')

	     do 510 k=1,nt
          write(*,*)   k
       read(77) t0     此行为报错的第17行