简单的 IO

作为写入输入和输出的示例，我们将获取实数值并返回值及其平方，直到用户输入负数。

如下所述，read 命令有两个参数：单元号和格式说明符。在下面的示例中，我们使用*作为单元号（表示 stdin）和*作为格式（在这种情况下表示 reals 的默认值）。我们还指定了 print 语句的格式。也可以使用 write(*,"The value....") 或者简单地忽略格式化并将其作为

print *,"The entered value was ", x," and its square is ",x*x

这可能会导致一些奇怪的间隔字符串和值。

program SimpleIO
   implicit none
   integer, parameter::wp = selected_real_kind(15,307)
   real(kind=wp) :: x
   
   ! we'll loop over until user enters a negative number
   print '("Enter a number >= 0 to see its square. Enter a number < 0 to exit.")'
   do
      ! this reads the input as a double-pricision value
      read(*,*) x
      if (x < 0d0) exit
      ! print the entered value and it's square
      print '("The entered value was ",f12.6,", its square is ",f12.6,".")',x,x*x
   end do
   print '("Thank you!")'
   
end program SimpleIO