香农的信息论是如何“量化”信息的？
How does Shannon's information theory 'quantify' information?
香农把信息量定义为事件不确定性的减少：一个发生概率为 p 的结果携带 -log₂ p 比特。由此推出熵 H=−Σ pᵢlog₂pᵢ 作为信源的平均信息量，并成为数据压缩与通信可靠性的理论极限。
Shannon defined information as reduced uncertainty: an outcome of probability p carries -log₂ p bits. This yields entropy H=−Σ pᵢlog₂pᵢ as the average information of a source, setting the limits of compression and reliable communication.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Charles Petzold,《Code: The Hidden Language of Computer Hardware and Software》第2版,Microsoft Press,2022
C. Petzold, Code, 2nd ed., Microsoft Press, 2022; Chinese ed.《编码》
#香农 #信息论
图灵机为什么被视为“计算”的理论模型？
Why is the Turing machine seen as the theoretical model of 'computation'?
图灵机用一条无限纸带、一个读写头和简单规则，就能模拟任何可机械执行的算法。丘奇-图灵论题认为：凡图灵机算得出的，就是“可有效计算”的全部，因此它是衡量计算能力边界的基准。
A Turing machine—an infinite tape, a head and simple rules—can simulate any mechanically executable algorithm. The Church-Turing thesis holds that whatever it computes is exactly 'effectively computable', making it the benchmark for computational limits.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Charles Petzold,《Code: The Hidden Language of Computer Hardware and Software》第2版,Microsoft Press,2022
C. Petzold, Code, 2nd ed., Microsoft Press, 2022; Chinese ed.《编码》
#图灵机 #理论
第一台电子计算机叫什么？
What was the first electronic computer called?
通常被认为最早的大型电子计算机是 1940 年代的 ENIAC，它用约一万八千个电子管运算，占地一房间，原本用于炮兵弹道计算。它标志着人类进入电子计算时代。
Often cited as the first large electronic computer, ENIAC (1940s) used about 18,000 vacuum tubes, filled a room, and was built for artillery ballistic calculations—marking the start of the electronic computing era.
难度 入门 · 适合 小学低段(6-8)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Charles Petzold,《Code: The Hidden Language of Computer Hardware and Software》第2版,Microsoft Press,2022
C. Petzold, Code, 2nd ed., Microsoft Press, 2022; Chinese ed.《编码》
#ENIAC #历史