program link
implicit none
type node
    character(20) name
    integer id
    integer score
    type(node),pointer ::next
end type

integer,parameter::num=3
type(node),pointer ::students

call init_all(students,num)
call show_all(students)
print*,"now,we add a student"
call add_node(students)
call show_all(students)
print*,"now,we delete the student"
call del_node(students)
call show_all(students)

contains 
subroutine add_node(pos)
type(node),pointer ::pos,tmp
allocate(tmp)
tmp%name="abc"
tmp%id=1
tmp%score=100
print*,"please input name,id,end score of one students"
read*,tmp%name,tmp%id,tmp%score
if(associated(pos%next)) then
tmp%next=>pos%next
pos%next=>tmp
else 
nullify(tmp%next)
pos%next=>tmp
end if
end subroutine

subroutine del_node(pos)
type(node),pointer ::pos,next
next=>pos%next
if(associated(next%next)) then
pos%next=>next%next
deallocate(next)
else
nullify(pos%next)
deallocate(next)
end if
end subroutine

subroutine show_all(pos)
type(node),pointer ::pos,tmp
integer ::cnt
cnt=1
print*,"all students are:"
tmp=>pos
do while(associated(tmp))
print*,cnt,"th ",tmp%name,tmp%id,tmp%score
tmp=>tmp%next
cnt=cnt+1
end do
end subroutine

subroutine init_all(pos,num)
type(node),pointer ::pos,tmp,walk
integer num
integer i

allocate(tmp)
nullify(tmp%next)
call add_node(tmp)
pos=>tmp%next
deallocate(tmp)
walk=>pos
do i=1,num-1
call add_node(walk)
walk=>walk%next
end do
end subroutine

end program link