雙語暢銷書《艾倫圖靈傳》第7章:運轉起來(64)
There was a further fundamental consideration besides that of discreteness, reliability and speed: that of sheer size.
There would have to be room on the 'tape' of a universal machine both for the 'description numbers' of the machines it had to imitate, and its workings.
通用機的紙帶，必須有足夠的空間來容納機器要執行的描述數，已及供它運行的工作空間。The abstract universal machine of 1936 was equipped with a 'tape' of infinite length, meaning that although at any stage the amount of tape used would be finite, it was assumed that as more space was required it could always be made available.
在1936年，抽象的通用機配置了無限長的紙帶，這意味着，雖然在任意時刻機器使用的紙帶長度總是有限的，但他假想了機器總是能夠滿足任何空間需求。
In a practical machine, space would always be limited in extent—and for that reason no physical machine could actually realise a truly universal machine.
但是在實際的機器上，空間總是有限的，因此，沒有一臺實際的機器可以成爲真正的通用機。Still, Alan had suggested in Computable Numbers that human memory was finite in extent.
艾倫還在《可計算數》中表明，人腦的記憶容量也是有限的，If this were so then the human brain itself could hold only a limited number of 'tables of behaviour', and a sufficiently large tape could contain them all.
倘若如此，那麼人腦就只能記住有限數量的行爲表，而且這些可以放進一個足夠長的紙帶。The finiteness of any practical machine would not, on this argument, debar it from having a brain-like quality.
從這個論點出發，實際機器的紙帶是否有限，並不影響它具有人腦的功能。The question was, however, how much 'tape' would be required for a machine that could actually be built: enough to make it interesting, but not more than would be technically feasible.
但問題是，實際建造一個機器，到底需要多長的紙帶？紙帶的長度要使機器具有足夠的能力，但又不能超越技術可行性。And how could such storage be arranged without inconceivable expense in terms of electronic valves?
還有，怎樣安排這些存儲，才能儘量避免使用過多的電子管？
