雙語暢銷書《艾倫圖靈傳》第7章:運轉起來(67)
His projected zeta-function machine would have well illustrated the point.
It was designed to calculate the zeta-function to within a certain accuracy of measurement.
它可以在一定的精度範圍內計算ζ函數。If he had then found that this accuracy was insufficient for his purpose of investigating the Riemann Hypothesis, and needed another decimal place, then it would have meant a complete reengineering of the physical equipment—with much larger gear-wheels, or a much more delicate balance.
如果他覺得這種精度不足以供他研究黎曼猜想，他需要更高的精度，那就需要徹底改造物理設備——用更大的齒輪，或者更精確的平衡。
Every successive increase in accuracy would demand new equipment.
要想提高精度，必須要更換新的設備。In contrast, if the values of the zeta-function were found by 'digital' methods—by pencil and paper and desk calculators—then an increase in accuracy might well entail a hundred times more work, but would not need any more physical apparatus.
相反地，如果ζ函數機是基於數字方法，比如紙、筆和臺式計算器，那麼如果要提高精度，就需要增加也許幾百倍的工作量，但卻不需要改變物理設備。This limitation in physical accuracy was the problem with the pre-war 'differential analysers', which existed to set up analogies (in terms of electrical amplitudes) for certain systems of differential equations.
戰前的差分機，就面臨着物理精度的問題。It was this question which set up the great divide between 'analogue' and 'digital'.
通過這一點，可以明顯地區分模擬方法和數字方法。Alan was naturally drawn towards the 'digital' machine, because the Turing machines of Computable Numbers were precisely the abstract versions of such machines.
艾倫顯然對數字機器更感興趣，因爲《可計算數》中的圖靈機，就是一個假想的數字機。His predisposition would have been reinforced by long experience with 'digital' problems in cryptanalysis—problems of which those working on numerical questions would be entirely ignorant, by virtue of the secrecy surrounding them.
艾倫有那麼長的一段經歷，都在研究密碼分析中的數字問題，這也加重了他對數字機的傾向。He was certainly not ignorant of analogue approaches to problem-solving.
但他也並沒有無視模擬方法，Apart from the zeta-function machine, the Delilah had an important 'analogue' aspect.
除了ζ函數機之外，黛麗拉機也具有模擬機的特點，It depended crucially on accurate measurement and transmission of the amplitudes, in contrast to the X-system, which made them 'digital'.
它依賴於對振幅的精確測量和發送，這使它與X系統有着本質的區別。
