November 2017
Beginner to intermediate
344 pages
7h 2m
Chinese
Content preview from 深入理解運算原理｜從簡單的機器到無所不能的程式
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第 2 章
形式的指稱語意使用抽象的數學物件（通常是函數）來指稱像是運算式和陳述式的程式
語言結構，而且因為數學的習慣，規定了如何估算函數之類的事物，這在指稱的操作意
識提供了直接的思考方式。我們採用了比較不正式的指稱語意思維，作為從某種語言到
另一種語言的編譯器，而這也是實際上大多數程式語言最後獲得執行的原因：
javac
將
Java 程式編譯成 bytecode，Java 虛擬機器會及時的將 bytecode 編譯成 x86 指令，接著
為了要在核心執行，CPU 會將每個 x86 指令解譯成類似 RISC 的微指令 ... 它在哪裡結
束？編譯器、虛擬機器還是一路往下？
程式最終當然會執行，因為語意之塔最終會將實際的機器觸底：半導體裡的電子，順從
物理定律
18
。計算機是維護這種不穩定結構的裝置，諸多複雜的轉釋層在另一轉譯層的
頂端平衡，允許諸如多點觸控手勢和
while
迴圈之類的人類想法逐漸轉化成矽元素和電
子的物理宇宙。
備擇
本章所見的諸多語意風格有許多不同的名稱。小步驟語意就是所謂的
結構化操作語意
（
structural operational semantic
）和
轉換語意
（
transition semantic
）；大步驟語意更常稱
為
自然語意
（
natural semantic
）或
關連語意
（
relational semantic
）；而指稱語意也稱為
定點語意
（
fixed-point semantic
）或
數學語意
（
mathematical semantic
）。
此外也還有其他的形式語意的風格，其中一種就是 ...
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