program gfill

*** load a grid file with a single value

      implicit double precision(a-h,o-z)
      parameter(len=1000000)
      character*88 fname
      logical makpos
      integer hrec(len)
      real*4  zrec(len),val
      equivalence(hrec(1),zrec(1))

      lout=2

      write(6,1)
    1 format('program gfill')

      write(6,'(a$)') 'Enter code for data kind (0=integer)  --> '
      read(5,*) ikind

      write(6,'(a$)') 'Enter min lon: '
      read(5,*) glomn
      write(6,'(a$)') 'Enter max lon: '
      read(5,*) glomx
      write(6,'(a$)') 'Enter # col: '
      read(5,*) nlo
      idglo=idnint((glomx-glomn)/dble(nlo-1)*720000.d0)
      dglo=dble(idglo)/720000.d0
      if(makpos(glomn)) continue
      if(makpos(glomx)) continue

      write(6,'(a$)') 'Enter min lat: '
      read(5,*) glamn
      write(6,'(a$)') 'Enter max lat: '
      read(5,*) glamx
      write(6,'(a$)') 'Enter # row: '
      read(5,*) nla
      idgla=idnint((glamx-glamn)/dble(nla-1)*720000.d0)
      dgla=dble(idgla)/720000.d0
      if(nlo.gt.len) stop 12345

      write(6,2)
    2 format('      grid output --> Enter file name: ',$)
      read(5,'(a)') fname
      open(lout,file=fname,status='new',form='unformatted')

      if(ikind.eq.0) then
        write(6,'(a$)') 'Enter integer value to fill grid: '
        read(5,*) ival
      else
        write(6,'(a$)') 'Enter real*4 value to fill grid: '
        read(5,*) val
      endif

*** write the grid

      write(lout) glamn,glomn,dgla,dglo,nla,nlo,ikind

      if(ikind.eq.0) then
        do 12 i=1,nlo
   12   hrec(i)=ival
        do 10 irow=1,nla
   10   write(lout) (hrec(i),i=1,nlo)
      else
        do 13 i=1,nlo
   13   zrec(i)=val
        do 11 irow=1,nla
   11   write(lout) (zrec(i),i=1,nlo)
      endif

      stop
      end
      logical function makpos(glon)

*** insure longitude is positive

      implicit double precision(a-h,o-z)

      makpos=.false.

    1 if(glon.lt.0.d0) then
        glon=glon+360.d0
        makpos=.true.
        go to 1
      endif

    2 if(glon.ge.360.d0) then
        glon=glon-360.d0
        go to 2
      endif

      return
      end