> Once upon a time, in a kingdom not far from here, a king summoned two
> of his advisors for a test. He showed them both a shiny metal box
> with two slots in the top, a control knob, and a lever. "What do you
> think this is?"
>
> One advisor, an engineer, answered first. "It is a toaster," he said.
> The king asked, "How would you design an embedded computer for it?"
> The engineer replied, "Using a four-bit microcontroller, I would
> write a simple program that reads the darkness knob and quantizes its
> position to one of 16 shades of darkness, from snow white to coal
> black. The program would use that darkness level as the index to a
> 16-element table of initial timer values. Then it would turn on the
> heating elements and start the timer with the initial value selected
> from the table. At the end of the time delay, it would turn off the
> heat and pop up the toast. Come back next week, and I'll show you a
> working prototype."
>
> The second advisor, a Systems Analyst, immediately recognized the
> danger of such short-sighted thinking. He said, "Toasters don't just
> turn bread into toast, they are also used to warm frozen waffles.
> What you see before you is really a breakfast food cooker. As the
> subjects of your kingdom become more sophisticated, they will demand
> more capabilities. They will need a breakfast food cooker that can
> also cook sausage, fry bacon, and make scrambled eggs. A toaster
> that only makes toast will soon be obsolete. If we don't look to the
> future, we will have to completely redesign the toaster in just a few
> years."
>
> "With this in mind, we can formulate a more intelligent solution to
> the problem. First, create a class of breakfast foods. Specialize
> this class into subclasses: grains, pork, and poultry. The
> specialization process should be repeated with grains divided into
> toast, muffins, pancakes, and waffles; pork divided into sausage,
> links, and bacon; and poultry divided into scrambled eggs,
> hard-boiled eggs, poached eggs, fried eggs, and various omelet
> classes."
>
> "The ham and cheese omelet class is worth special attention because
> it must inherit characteristics from the pork, dairy, and poultry
> classes. Thus, we see that the problem cannot be properly solved
> without multiple inheritance. At run time, the program must create
> the proper object and send a message to the object that says, 'Cook
> yourself.' The semantics of this message depend, of course, on the
> kind of object, so they have a different meaning to a piece of toast
> than to scrambled eggs."
>
> "Reviewing the process so far, we see that the analysis phase has
> revealed that the primary requirement is to cook any kind of
> breakfast food. In the design phase, we have discovered some derived
> requirements. Specifically, we need an object-oriented language with
> multiple inheritance. Of course, users don't want the eggs to get
> cold while the bacon is frying, so concurrent processing is required,
> too."
>
> "We must not forget the user interface. The lever that lowers the
> food lacks versatility, and the darkness knob is confusing. Users
> won't buy the product unless it has a user-friendly, graphical
> interface. When the breakfast cooker is plugged in, users should see
> a cowboy boot on the screen. Users click on it, and the message
> 'Booting UNIX v. 8.3' appears on the screen. (UNIX 8.3 should be out
> by the time the product gets to the market.) Users can pull down a
> menu and click on the foods they want to cook."
> "Having made the wise decision of specifying the software first in the
> design phase, all that remains is to pick an adequate hardware
> platform for the implementation phase. An Intel 80386 with 8MB of RAM,
> a 30MB hard disk, and a VGA monitor should be sufficient. If you
> select a multitasking, object oriented language that supports multiple
> inheritance and has a built-in GUI, writing the program will be a snap.
> Imagine the difficulty we would have had if we had foolishly allowed
> hardware-first design strategy to lock us into a four-bit
> microcontroller !"
>
> The wise king had the systems analyst beheaded, and everyone lived
> happily ever after.