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The Pattern on the Stone: The Simple Ideas that Make Computers Work by W. Daniel Hillis

1998, 164 pages. $21. Basic Books/Perseus Books.

Computers so dominate our lives that we get lost in the details of one version of software after another, one generation of computers after another, and the current tangle of features, bugs, applications, and standards. The future of all that is appalling to contemplate. What a relief, then, to have Danny Hillis stroll with us through the basics, pointing out the simple things that continue to pertain decade after decade at the heart of these ambitious machines. When (if!) quantum computers come with their many-thousand-fold new capabilities, the same basics will apply. Knowing them makes the revolutions more manageable.

Computer basics are so simple, subtle, and potent that they elude even many professionals. Ingenious inventions themselves, they are powerful tools of invention on a par with language and mathematics. Hillis is the devisor and developer of massive parallel processing, which runs the current generation of supercomputers and lately employs the Net for distributed supercomputing in modest machines. He writes with authority and clarity both about the basics (he once made a working computer of Tinker Toys) and about what is coming as computers learn to generate capabilities the equal of ours, and beyond. ?Stewart Brand (courtesy Global Business Network)

"In a sense, communication and storage are just two aspects of the same thing: communication sends a message from one place to another; storage "sends" a message from one time to another.

"Programmed computers, including their software, are by far the most complex systems ever designed by human beings. The number of interacting components in a computer is orders of magnitude larger than the number of components in the most complex airplane. Modern engineering methods are not really up to designing objects of such complexity.

"Most scientists would be surprised if quantum mechanics succeeds in providing a kind of computer more powerful than a Turing machine, but science makes progress through a series of surprises. If you're hoping to be surprised by a new sort of computer, quantum mecha-nics is a good area to keep an eye on.

"Here I must pause to mention the bit. The smallest "difference that makes a difference" (to use Bateson's phrase again) is a difference that splits all signals into two distinct classes. In the tic-tac-toe machine, the two classes are "current flowing" and "no current flowing." By convention, we call these two possible classes 1 and 0. These are just names; we could as easily call them True or False, or Alice and Bob. Even the choice of which class is called 0 and which is called 1 is arbitrary. A signal that can carry one of the two different messages (like 1 or 0) is called a binary signal or a bit.

"Unlike most books on computers?which are either about how to use them or about the technology out of which they're built (ROM, RAM, disk drives, and so on)?this is a book about ideas. It explains, or at least introduces, most of the important ideas in the field of computer science, including Boolean logic, finite-state machines, programming languages, compilers and interpreters, Turing universality, information theory, algorithms and algorithmic complexity, heuristics, uncomputable functions, parallel computing, quantum computing, neural networks, machine learning, and self-organizing systems.


ISBN: 046502596X

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