[输入输出] 關於字符串和数字的转换問題

program ZWD_gamit
implicit none

  integer :: stat,stat2,stat3,stat4,yr,dayofyear,hr
  character :: filename_ztd*12,filename_zhd*12,filename_zwd*12,first*1
  real :: time_all_ztd,time_all_zhd,ztd_m,zhd_mm,ztd_mm,zwd_mm

  open(11,file="list.txt")
  close(11,status="delete")
  open(22,file="list2.txt")
  close(22,status="delete")
  call system('for %f in (*_all.ztd) do echo %f >> list.txt')
  call system('for %f in (*_all.zhd) do echo %f >> list2.txt')
  open (11,file="list.txt")
  open (22,file="list2.txt")

  stat=0
  stat2=0
  do while (stat==0 .and. stat2==0)
    read (11,"(a12)",iostat=stat) filename_ztd
    read (22,"(a12)",iostat=stat2) filename_zhd
    if (stat/=0 .and. stat2/=0) exit
    open (33,file=filename_ztd)
    open (44,file=filename_zhd)
    filename_zwd=filename_ztd(1:8)//".zwd"
    open (55,file=filename_zwd)
    
    stat3=0
    do while (stat3==0)
      read (33,50,iostat=stat3) time_all_ztd,ztd_m,yr,dayofyear,hr
50    format (f12.7,4x,f6.1,3x,i4,3x,i3.3,3x,i2.2)
      if (stat3/=0) exit
      stat4=0
      do while (stat4==0)
        read (44,100,iostat=stat4) time_all_zhd,zhd_mm
100     format (f12.7,4x,f6.1)
        if (stat4/=0) exit          
        if (time_all_ztd==time_all_zhd) then
          read (zhd_mm(1:1),"(a1)") first
          if( first/="*") then
            ztd_mm = ztd_m*1000D0
            zwd_mm = ztd_mm - zhd_mm
            write (55,150) time_all_ztd,zwd_mm,yr,dayofyear,hr
150         format (f12.7,3x,f12.7,3x,i4,3x,i3.3,3x,i2.2)
          end if 
        end if
      end do
      rewind(44)
    end do
    close(33)
    close(44) 
    close(55)
  end do    
  close(11)
  close(22)
end program

character( len = 30 ) c_zhd_mm !// c_zhd_mm 定义为字符型
do while (stat4==0)
  read (44,*,iostat=stat4) time_all_zhd,c_zhd_mm !// 通常 * 就足够 read 了
  if (stat4/=0) exit         
  if (time_all_ztd==time_all_zhd) then
    !read (zhd_mm(1:1),"(a1)") first !//这句去掉
    if( c_zhd_mm(1:1) /= "*") then
      read( c_zhd_mm , * ) zhd_mm !// 如果有数值，再从 c_zhd_mm 中读取 zhd_mm
      ztd_mm = ztd_m*1000D0
      zwd_mm = ztd_mm - zhd_mm