c  read an arbitrary file of columns of data. If there are characters in a line
c  other than number,commas,periods or minus signs then the line is
c  interpreted as a comment line. Data sets are dileneated by comment lines.
c  Each row of data appears in array column(19). Here we read two files
c  and write out the difference of the last data sets in each.
	character*59 first,second
	character*264 string
	real column(19),value(19,1000,2)
c	do ifile=1,2
	ifile=1
	if(ifile.eq.1)call strget(' first file ?',first)
c	if(ifile.eq.2)call strget(' second file ?',first)
        type 3
 3      format(' Which columns for x and y ?',$)
        read(5,4)ix,iy
 4      format(2i)
	idata=0
	open(unit=1,file=first,readonly,type='OLD')
10	read(1,1,end=99)string
c       write(6,1)string
1	format(a132)
	call com_or_data(string,id)  !id=0 for comment line, 1 for data
	if(id.eq.0)then
	open(unit=13,file='new_'//first,type='new')
c	  write(13,1)string  !comment line, write it out and read next
	  idata=0  !comment line indicates new data set
	  goto 10
	endif
	if(id.eq.1)then !data
	  idata=idata+1  !row of data
	  call data_line(string,ncolumns,column)
	  do j=1,ncolumns
	    value(j,idata,ifile)=column(j)
	    end do
	endif
2	format(1x,7e9.4)
c	type 2,(column(j),j=1,ncolumns)
	goto 10
99	continue
c	end do !ifile
	  do i=1,idata
	  write(13,5)value(ix,i,1),value(iy,i,1)
 5        format(1x,2e12.3)
	  end do !i
	end