内容简介

Every day, we use our computers to perform remarkable feats. A simple web search picks out a handful of relevant needles from the world's biggest haystack: the billions of pages on the World Wide Web. Uploading a photo to Facebook transmits millions of pieces of information over numerous error-prone network links, yet somehow a perfect copy of the photo arrives intact. Without even knowing it, we use public-key cryptography to transmit secret information like credit card numbers; and, we use digital signatures to verify the identity of the websites we visit. How do our computers perform these tasks with such ease? This is the first book to answer that question in language anyone can understand, revealing the extraordinary ideas that power our PCs, laptops, and smartphones. Using vivid examples, John MacCormick explains the fundamental "tricks" behind nine types of computer algorithms, including artificial intelligence (where we learn about the "nearest neighbor trick" and "twenty questions trick"), Google's famous PageRank algorithm (which uses the "random surfer trick"), data compression, error correction, and much more. These revolutionary algorithms have changed our world: this book unlocks their secrets, and lays bare the incredible ideas that our computers use every day.

作者简介

约翰·麦考密克，JohnMacCormick，计算机科学的领头人和导师。

获得牛津大学博士学位，曾经在惠普和微软从事研究工作。现在在迪金森学院担任计算机学科的教授。并且是多项专利的所有者。

精彩摘录

ThedebateoverthevalidityoftheChurch-Turingthesisrageson.Butifitsstrongestversionholds,thenourcomputersaren'ttheonlyoneshumbledbythelimitsofundecidability.Thesamelimitswouldapplynotonlytothegeniusatourfingertips,butthegeniusbehindthem:ourownminds.

——引自章节：Whatiscomputable?

【第一步】你和阿诺德各自单独选择一个私人数字（你8，阿诺德9）。【第二步】你和阿诺德公开就两个公开数字达成一致：钟大小（本例为11）和另一个被称为基数的数字（本例为2）。【第三步】通过使用幂符号和钟算，你和阿诺德各自将自己的私人数字和公开数字想混，分别得到一个公开——私人数字（public-privatenumber，PPN）。你的PPN=2的（8次幂）=3（钟大小为11）阿诺德的PPN=2的（9次幂）=6（钟大小为11）【第四步】你和阿诺德各自单独获得对方的公开——私人数字，在和自己的私人数字相混合。共享密钥=其他人的PPN的（私人数字次幂）（钟大小）你的共享密钥=6的8次幂=4（钟大小为11）阿诺德的共享密钥=3的9次幂（钟大小为11）

——引自第60页