Date: Fri, 5 Nov 1999 17:42:02 -0600
Reply-To: dave <dave@251.ORG>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: dave <dave@251.ORG>
Subject: Re: Computerized Gauge Setup <FRIDAY HUMOR>
Content-Type: text/plain; charset="iso-8859-1"
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 Electrical Engineer, answered first. "It is a toaster," he said.
The king asked, "How would you design an embedded computer for it?" The
advisor: "Using a four-bit microcontroller, I would write a simple program
that reads the darkness knob and quantifies 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 software developer, 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 Pentium with 48MB
of memory, a 1.2GB hard disk, and a SVGA monitor should be sufficient. If
you select a multitasking, object oriented language that supports multiple
inheritance and has a uilt-in GUI, writing the program will be a snap." The
king wisely had the software developer beheaded,and they all lived happily
ever after.
dave :)
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