(nil): doufexi ioanna (doufexi(@)students.uiuc.edu)
Ημερομηνία: Τρι 06 Φεβ 1996 - 08:49:11 EET

• Μηνύματα ταξινομημένα ανά: [ ημερομηνία ] [ thread ] [ θέμα ] [ συγγραφέα ] [ Επισυναπτόμενο ]
• Mail ενέργειες: [ Απάντησε σε αυτό το μήνυμα ] [ Στείλε ενα καινούριο μήνυμα ]

This is long but it's a good one:

     
     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 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. 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
     memory, 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 a hardware-first design strategy to lock us into a
     four-bit microcontroller!)."
     
     The king wisely had the computer scientist beheaded, and they all
     lived happily ever after.

• Επόμενο μήνυμα: Zachary De Pian: "Mouse Balls"
• Προηγούμενο μήνυμα: zpian(@)intranet.gr: "Condom Jokes"
• Μηνύματα ταξινομημένα ανά: [ ημερομηνία ] [ thread ] [ θέμα ] [ συγγραφέα ] [ Επισυναπτόμενο ]
• Mail ενέργειες: [ Απάντησε σε αυτό το μήνυμα ] [ Στείλε ενα καινούριο μήνυμα ]