雙語暢銷書《艾倫圖靈傳》第7章:運轉起來(69)
After working on a 'Difference Engine', to mechanise the particular numerical method used in the construction of mathematical tables, Babbage had conceived (by 1837) of an Analytical Engine, whose essential property was that of mechanising any mathematical operation.
It embodied the crucial idea of replacing the engineering of different machines for different tasks, by the office work of producing new instructions for the same machine.
這就體現了在做不同的工作時，可以通過設計新的指令，而不是設計新的設備，這是非常重要的思想。Babbage did not have a theory like that of Computable Numbers, to argue for universality, and his attention was focussed upon operations using numbers in decimal notation.
巴貝奇沒有《可計算數》這樣的理論來證明其通用性，他的注意力集中在十進制的數值運算，但他也確信這種機制可以執行任何符號運算注。
Yet he did perceive that its mechanism could serve to effect operations upon symbols of any kind whatever, and in this and other ways the Analytical Engine came close in its conception to the Universal Turing Machine.
分析引擎和通用圖靈機，在很多方面都有相似之處。Babbage wanted a 'scanner', in effect, working on a stream of instructions, and putting them into operation.
巴貝奇也需要一個"掃描器"，在一串指令上來回操作。He hit on the idea of coding the instructions on punched cards, such as then were used for the weaving of complicated patterns in brocade.
他想到了把指令做成打孔卡片，從而使織機可以自動在錦緞上織出複雜的圖案。His plans also called for storing numbers in the form of positions of gear wheels. Each instruction card would cause an arithmetical operation such as 'subtract the number in location 5 from that in location 8, and put the result in location 16.'
他還打算用齒輪的位置來存儲數值。每一張指令卡片會執行一次算術操作，比如"用5號位置的數減去8號位置的數，並將結果存到16號位置"。This required machinery he called the 'mill' to do the arithmetical operations, but the crucial innovation of Babbage's plans did not lie in the efficient mechanisation of adding and multiplying.
他把執行算術運算的部件稱爲"作坊"。但是，巴貝奇計劃的重要創新之處，並不在於機械運算，It lay in his perception that it was the mechanisation of the organising or logical control of the arithmetic that mattered.
而是在於他發現了，對算術過程的組織和邏輯控制纔是最重要的。In particular, Babbage had the vital idea that it must be possible to move forwards or backwards among the stream of instruction cards, skipping or repeating, according to criteria which were to be tested by the machine itself in the course of its calculation.
特別是，巴貝奇有一個關鍵的想法是，機器必須能夠在一串指令卡片中來回遍歷，並根據實際計算的情況，來決定跳過或重複。This idea, that of 'conditional branching', was his most advanced.
這種"條件分支"的想法，是他最先進的地方。It was equivalent to the freedom allowed to Turing machines, that of changing 'configuration' according to what was read on the tape, and it was this that made Babbage's planned machine a universal one, as he himself was well aware.
而這種自主性，與圖靈機是等價的，圖靈機就是根據紙帶上的指令來切換機器的狀態。巴貝奇很清楚，正是這一點，使他的機器具有通用的特性。
