Again, fwrite problem

[G Mark]

>The Fortran77 program is:
>open(21,file='grads.fwrite',status='old',form='unformatted',recl=41*32)
>do t=1,tt
> do k=1,L
>  inum=k+(t-1)*L
>  read(21,rec=inum) ((data(i,j,k),i=1,41),j=1,32)
> enddo
>enddo
>
>The program of Fortran77 is correct.
>But when I execute the program, some kinds of errors happen:
>forrtl: Not a typewriter
>forrtl: severe(39): error during read, unit 21, file grads.fwrite
>
>If the variables, times of fwrite data increase, the error become:
>forrtl: Bad file number
>forrtl: severe(39): error during read, unit 21, file grads.fwrite

Hi all
Finally, I find where the problem is.
Because I didn't put access in the open file line of the f77 program.
.......
Sorry waste your time.

Mark