[求助] 想一个一个读出一行的每个单词，但是这个程序不运行··

program main
  character,allocatable:: word(:)
  character spliter,substring
  integer id,len_spliter,len_substring
  integer,parameter ::ncol=4
  allocate(word(ncol))
  open(unit=12,file='a.txt')
  read(12,*) substring
  write(*,*)'分隔符:'
  read(*,*)spliter
  len_spliter=len(spliter)
  do i=1,ncol
    len_substring=len(substring)
    id=index(trim(substring),spliter)
    substring=substring(1:(id-1))
    word(i)=substring
    write(*,*) word(i)
    substring=substring((id+len_spliter):len_substring)
 end do
 stop
end 

program main
  character(80),allocatable:: word(:)
  character(80) substring, spliter
  integer i, id,len_spliter,len_substring
  integer,parameter ::ncol=4
  allocate(word(ncol))
  open(unit=12,file='a.txt')
  read(12,'(A)') substring
  write(*,*)'分隔符:'
  read(*,*)spliter
  len_spliter=len(trim(spliter))
  substring = adjustl(substring)
  len_substring=len(trim(substring))
  do i=1,ncol-1
    id=index(substring,trim(spliter))
    word(i)=substring(1:(id-1))
    write(*,*) trim(word(i))
    substring=substring((id+len_spliter):)
  end do
  word(ncol)=substring
  write(*,*) trim(word(ncol))
pause
end