ask, "Is this new question a worthy one to investigate?" This latter question we investigate without further ado, thereby cutting short an infinite regress.员工自我工作总结
The new problem has the advantage of drawing a fairly sharp line between the physical and the intellectual capacities of a man. No engineer or chemist claims to be able to produce a material which is indistinguishable from the human skin. It is possible that at some time this might be done, but even supposing this invention available we should feel there was little point in trying to make a "thinking machine" more human by dressing it up in such artificial flesh. The form in which we have t the problem reflects this fact in the condition which prevents the interrogator from eing or touching the other competitors, or hearing -their voices. Some other advantages of the propod criterion may be shown up by specimen questions and answers. Thus:
Q: Plea write me a sonnet on the subject of the Forth Bridge.国庆放假通知
A : Count me out on this one. I never could write poetry.
Q: Add 34957 to 70764.
A: (Pau about 30 conds and then give as answer) 105621.
Q: Do you play chess?
A: Yes.
Q: I have K at my K1, and no other pieces. You have only K at K6 and R at R1. It is your move. What do you play?
A: (After a pau of 15 conds) R-R8 mate.
The question and answer method ems to be suitable for introducing almost any one of the fields of human endeavour that we wish to include. We do not wish to penali the machine for its inability to shine in beauty competitions, nor to penali a man for losing in a race against an aeroplane. The conditions of our game make the disabilities irrelevant. The "witness" can brag, if they consider it advisable, as much as they plea about their charms, strength or heroism, but the interrogator cannot demand practical demonstrations.
The game may perhaps be criticid on the ground that the odds are weighted too heavily against the machine. If the man were to try and pretend to be the machine he would clearly make a very poor showing. He would be given away at once by slowness and inaccuracy in arithmetic. May not m
achines carry out something which ought to be described as thinking but which is very different from what a man does? This objection is a very strong one, but at least we can say that if, nevertheless, a machine can be constructed to play the imitation game satisfactorily, we need not be troubled by this objection.
It might be urged that when playing the "imitation game" the best strategy for the machine may possibly be something other than imitation of the behaviour of a man. This may be, but I think it is unlikely that there is any great effect of this kind. In any ca there is no intention to investigate here the theory of the game, and it will
be assumed that the best strategy is to try to provide answers that would naturally be given by a man.
3. The Machines Concerned in the Game
The question which we put in 1 will not be quite definite until we have specified what we mean by the word "machine." It is natural that we should wish to permit every kind of engineering technique to be ud in our machines. We also wish to allow the possibility than an engineer or team of engineers may construct a machine which works, but who manner of operation cannot be satisfactorily descr
ibed by its constructors becau they have applied a method which is largely experimental. Finally, we wish to exclude from the machines men born in the usual manner. It is difficult to frame the definitions so as to satisfy the three conditions. One might for instance insist that the team of engineers should be all of one x, but this would not really be satisfactory, for it is probably possible to rear a complete individual from a single cell of the skin (say) of a man. To do so would be a feat of biological technique derving of the very highest prai, but we would not be inclined to regard it as a ca of "constructing a thinking machine." This prompts us to abandon the requirement that every kind of technique should be permitted. We are the more ready to do so in view of the fact that the prent interest in "thinking machines" has been aroud by a particular kind of machine, usually called an "electronic computer" or "digital computer." Following this suggestion we only permit digital computers to take part in our game.
This restriction appears at first sight to be a very drastic one. I shall attempt to show that it is not so in reality. To do this necessitates a short account of the nature and properties of the computers.
It may also be said that this identification of machines with digital computers, like our criterion for "thinking," will only be unsatisfactory if (contrary to my belief), it turns out that digital computers are unable to give a good showing in the game. There are already a number of digital computers in work
工作思考ing order, and it may be asked, "Why not try the experiment straight away? It would be easy to satisfy the conditions of the game. A number of interrogators could be ud, and statistics compiled to show how often the right identification was given." The short answer is that we are not asking whether all digital computers would do well in the game nor whether the computers at prent available would do well, but whether there are imaginable computers which would do well. But this is only the short answer. We shall e this question in a different light later.
4. Digital Computers
The idea behind digital computers may be explained by saying that the machines are intended to carry out any operations which could be done by a human computer. The human computer is suppod to be following fixed rules; he has no authority to deviate from them in any detail. We may suppo that the rules are supplied in a book, which is altered whenever he is put on to a new job. He has also an unlimited supply of paper on which he does his calculations. He may also do his multiplications and additions on a "desk machine," but this is not important.
陈小春独家记忆
If we u the above explanation as a definition we shall be in danger of circularity of argument. We avoid this by giving an outline. of the means by which the desired effect is achieved. A digital computer can usually be regarded as consisting of three parts:
(i) Store.
(ii) Executive unit.
(iii) Control.
The store is a store of information, and corresponds to the human computer's paper, whether this is the paper on which he does his calculations or that on which his book of rules is printed. In so far as the human computer does calculations in his bead a part of the store will correspond to his memory.
The executive unit is the part which carries out the various individual operations involved in a calculation. What the individual operations are will vary from machine to machine. Usually fairly lengthy operations can be done such as "Multiply 3540675445 by 7076345687" but in some machines only very simple ones such as "Write down 0" are possible.
We have mentioned that the "book of rules" supplied to the computer is replaced in the machine by a part of the store. It is then called the "table of instructions." It is the duty of the control to e that the instructions are obeyed correctly and in the right order. The control is so constructed that this necessarily happens.
迭句
The information in the store is usually broken up into packets of moderately small size. In one machine, for instance, a packet might consist of ten decimal digits. Numbers are assigned to the parts of the store in which the various packets of information are stored, in some systematic manner. A typical instruction might say-"Add the number stored in position 6809 to that in 4302 and put the result back into the latter storage position."
Needless to say it would not occur in the machine expresd in English. It would more likely be coded in a form such as 6809430217. Here 17 says which of various possible operations is to be performed on the two numbers. In this ca the)e operation is that described above, viz., "Add the number. . . ." It will be noticed that the instruction takes up 10 digits and so forms one packet of information, very conveniently. The control will normally take the instructions to be obeyed in the order of the positions in which they are stored, but occasionally an instruction such as
"Now obey the instruction stored in position 5606, and continue from there"
may be encountered, or again反义疑问句回答规则
"If position 4505 contains 0 obey next the instruction stored in 6707, otherwi continue straight on."
desting
Instructions of the latter types are very important becau they make it possible
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for a quence of operations to be replaced over and over again until some condition is fulfilled, but in doing so to obey, not fresh instructions on each repetition, but the same ones over and over again. To take a domestic analogy. Suppo Mother wants Tommy to call at the cobbler's every morning on his way to school to e if her shoes are done, she can ask him afresh every morning. Alternatively she can stick up a notice once and for all in the hall which he will e when he leaves for school and which tells him to call for the shoes, and also to destroy the notice when he comes back if he has the shoes with him.
The reader must accept it as a fact that digital computers can be constructed, and indeed have been constructed, according to the principles we have described, and that they can in fact mimic the actions of a human computer very cloly.
The book of rules which we have described our human computer as using is of cour a convenient fiction. Actual human computers really remember what they have got to do. If one wants to make a machine mimic the behaviour of the human computer in some complex operation one has to ask him how it is done, and then translate the answer into the form of an instruction table. Constructing instruction tables is usually described as "programming." To "programme a machine to carry out the operation A" means to put the appropriate instruction table into the machine so that it will do A.
An interesting variant on the idea of a digital computer is a "digital computer with a random element." The have instructions involving the throwing of a die or some equivalent electronic process; one such instruction might for instance be, "Throw the die and put the-resulting number into store 1000." Sometimes such a machine is described as having free will (though I would not u this phra mylf), It is not normally possible to determine from obrving a machine whether it has a random element, for a similar effect can be produced by such devices as making the choices depend on the digits of the decimal for .
Most actual digital computers have only a finite store. There is no theoretical difficulty in the idea of a computer with an unlimited store. Of cour only a finite part can have been ud at any one time. Likewi only a finite amount can have been constructed, but we can imagine more and more being added as required. Such computers have special theoretical interest and will be called infinitive capacity computers.
The idea of a digital computer is an old one. Charles Babbage, Lucasian Professor of Mathematics at Cambridge from 1828 to 1839, planned such a machine, called the Analytical Engine, but it was never completed. Although Babbage had all the esntial ideas, his machine was not at that time such a very attractive prospect. The speed which would have been available would be definitely fast
er than a human computer but something like I 00 times slower than the Manchester machine, itlf one of the slower of the modern machines, The storage was to be purely mechanical, using wheels and cards.
The fact that Babbage's Analytical Engine was to be entirely mechanical will help us to rid ourlves of a superstition. Importance is often attached to the fact that modern digital computers are electrical, and that the nervous system also is electrical. Since Babbage's machine was not electrical, and since all digital
