congratulations you and i have forwarded the same exact thing
tj
- Original Message -
From: Onj [EMAIL PROTECTED]
To: talk2 talk2@AndreLouis.COM
Sent: Thursday, September 28, 2006 11:36 AM
Subject: The Talk2 List Hardware vs. Software
Once upon a time, in an absolute monarchy 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.
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.
Wait 'til next week, and I'll show you a working prototype.
The second advisor, a computer scientist, 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. Would-be diners
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 80586 with 16MB of memory, a
1.2GB hard disk, and a SuperVGA 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 a
hardware-first design strategy to lock us into a four-bit
microcontroller).
The king wisely had the computer scientist beheaded, and the kingdom
lived happily ever after.
Andre P. Louis
Uncopyright, free music, compositions, Web-hosting and the new look to the
beyond Radio Network? Visit one of the sites listed below:
Main site: http://AndreLouis.COM
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