! original BASIC code at
! https://www.retrobrewcomputers.org/forum/index.php?t=msg&th=201&goto=4704&#msg_4704
! translated Fortran90 code, CC0

program asciiart_benchmark
  integer :: x, y, i
  real :: a, b, ca, cb, t
  character :: c*17 = '0123456789ABCDEF '

  do y = -12, 12
     do x = -39, 39
        ca = x * 0.0458
        cb = y * 0.08333
        a = ca
        b = cb

        do i = 1, 16
           t = (a * a) - (b * b) + ca
           b = (2 * a * b) + cb
           a = t

           if ((a * a + b * b) > 4) exit
        end do

        write(*, fmt='(a1)', advance='no') c(i:i)
     end do

     write(*, fmt='(a1)')
  end do
  
end program asciiart_benchmark