program rw
 implicit none
 character(20):: fn1,fn2
 real(16), parameter:: pi26=3.1415926535897932384626434_16 
 real(16), parameter:: e26= 2.7182818284590452353602875_16
 integer(8):: N
 real(16):: x16,d16,ref
 integer:: i,k,j,p(3)
 character(2):: prec
 character(3):: tst
 
 p=(/32, 64, 80/)
 
 do j=1,2
   if(j==1) then 
      tst="E_"; ref=e26
   elseif(j==2) then
      tst="PI_"; ref=pi26
   endif
     do i=1,3  !precision
        write(prec,'(i2)') p(i)
        fn1= trim(tst)//prec//".dat"
        fn2= trim(tst)//prec//"_err.dat"
        open(1,file=fn1,status='old')
        open(2,file=fn2)
        do !read end of the file
          read(1,*,end=11) k,N,x16
            d16=(x16-ref)/ref
          if(i==1) write(2,*) k,N,real(x16,4), real(d16)
          if(i==2) write(2,*) k,N,real(x16,8), real(d16)
          if(i==3) write(2,*) k,N,real(x16,10), real(d16)
        enddo
11     continue
       close(1)
       close(2)
  enddo !i
 enddo !j

end program