我是在看一本书的附录时，看到这篇文章的，很有道理（Linux programming by example, The Fundamentals）
于是在网上，我找到了文章的电子版本，地址为
为什么每个人都急不可耐？
走进任何一家书店，你会看见《Teach Yourself Java in 7 Days》（7天Java无师自通）的旁边是一长排看不到尽头的类似书籍，它们要教会你Visual Basic、Windows、Internet等等，而只需要几天甚至几小时。我在上进行了如下：
(出版日期：1992年后 and 书名：天 and （书名：学会 or 书名：无师自通）)
我一共得到了248个搜索结果。前面的78个是计算机书籍（第79个是《》，30天学会孟加拉语）。我把关键词“days”换成“hours”，得到了非常相似的结果：这次有253本书，头77本是计算机书籍，第78本是《》（24小时学会文法和文体）。头200本书中，有96%是计算机书籍。
结论是，要么是人们非常急于学会计算机，要么就是不知道为什么计算机惊人地简单，比任何东西都容易学会。没有一本书是要在几天里教会人们欣赏贝多芬或者量子物理学，甚至怎样给狗打扮。
让我们来分析一下像《》（3天学会Pascal）这样的题目到底是什么意思：
- 学会：在3
天时间里，你不够时间写一些有意义的程序，并从它们的失败与成功中学习。你不够时间跟一些有经验的程序员一起工作，你不会知道在那样的环境中是什么滋味。
简而言之，没有足够的时间让你学到很多东西。所以这些书谈论的只是表面上的精通，而非深入的理解。如Alexander Pope（译注：英国诗人、作
家，1688-1744）所言，一知半解是危险的（a little learning is a dangerous thing）
。
- Pascal：在3
天时间里你可以学会Pascal的语法（如果你已经会一门类似的语言），但你无法学到多少如何运用这些语法。简而言之，如果你是，比如说一个Basic程
序员，你可以学会用Pascal语法写出Basic风格的程序，但你学不到Pascal真正的优点（和缺点）。那关键在哪里？（译
注：ACM第一任主席，图灵奖得主，1922-1990）曾经说过：“如果一门语言不能影响你对编程的想法，那它就不值得去学”。另一种观点是，有时候你
不得不学一点Pascal（更可能是Visual Basic和JavaScript之类）的皮毛，因为你需要接触现有的工具，用来完成特定的任务。但此
时你不是在学习如何编程，你是在学习如何完成任务。
- 3天：不幸的是，这是不够的，正如下一节所言。
10年编程无师自通
一些研究者（、）
的研究表明，在许多领域，都需要大约10 年时间才能培养出专业技能，包括国际象棋、作曲、绘画、钢琴、游泳、网球，以及神经心理学和拓扑学的研究。似乎
并不存在真正的捷径：即使是莫扎特，他4 岁就显露出音乐天才，在他写出世界级的音乐之前仍然用了超过13年时间。再看另一种音乐类型的代表--披头士，
他们似乎是在1964年的Ed Sullivan节目中突然冒头的。但其实他们从1957年就开始表演了，即使他们很早就显示出了巨大的吸引力，他们第一
次真正的成功之作《Sgt. Peppers》也要到1967年才发行。Samuel Johnson（译注：英国诗人）认为10 年还是不够的：“任何
领域的卓越成就都只能通过一生的努力来获得；稍低一点的代价也换不来。”
（Excellence in any department can be attained only by the labor of a lifetime;
it is not to be purchased at a lesser price.） 乔叟（译注：Chaucer，英国诗人，1340-
1400）也抱怨说：“生命如此短暂，掌握技艺却要如此长久。”（the lyf so short,
the craft so long to lerne.）
下面是我在编程这个行当里获得成功的处方：
- 对编程感兴趣，因为乐趣而去编程。确定始终都能保持足够的乐趣，以致你能够将10年时间投入其中。
- 跟其他程序员交谈；阅读其他程序。这比任何书籍或训练课程都更重要。
- 编程。最好的学习是。用更加技术性的语言来讲，“个体在特定领域最高水平的表现不是作为长期的经验的结果而自动获得的，但即使是非常富有经验的个体也可以通过刻意的努力而提高其表现水平。”（），而且“最有效的学习要求为特定个体制定适当难度的任务，有意义的反馈，以及重复及改正错误的机会。”（p. 20-21）《》（在实践中认知：心智、数学和日常生活的文化）是关于这个观点的一本有趣的参考书。
- 如
果你愿意，在大学里花上4年时间（或者再花几年读研究生）。这能让你获得一些工作的入门资格，还能让你对此领域有更深入的理解，但如果你不喜欢进学校，
（作出一点牺牲）你在工作中也同样能获得类似的经验。在任何情况下，单从书本上学习都是不够的。“计算机科学的教育不会让任何人成为内行的程序员，正如研
究画笔和颜料不会让任何人成为内行的画家”，Eric Raymond，《The New Hacker's Dictionary》（新黑客字典）的作
者如是说。我曾经雇用过的最优秀的程序员之一仅有高中学历；但他创造出了许多，甚至有讨论他本人的，而且股票期权让他达到我无法企及的富有程度（译注：指，XEmacs和Netscape Navigator的作者）。
- 跟别的程序员一起完成项目。在一些项目中成为最好的程序员；在其他一些项目中当最差的一个。当你是最好的程序员时，你要测试自己领导项目的能力，并通过你的洞见鼓舞其他人。当你是最差的时候，你学习高手们在做些什么，以及他们不喜欢做什么（因为他们让你帮他们做那些事）。
- 接手别的程序员完成项目。用心理解别人编写的程序。看看在没有最初的程序员在场的时候理解和修改程序需要些什么。想一想怎样设计你的程序才能让别人接手维护你的程序时更容易一些。
- 学
会至少半打编程语言。包括一门支持类抽象（class abstraction）的语言（如Java或C++），一门支持函数抽象
（functional abstraction）的语言（如Lisp或ML），一门支持句法抽象（syntactic abstraction）的语言
（如Lisp），一门支持说明性规约（declarative specification）的语言（如Prolog或C++模版），一门支持协程
（coroutine）的语言（如Icon或Scheme），以及一门支持并行处理（parallelism）的语言（如Sisal）。
- 记住在“计算机科学”这个词组里包含“计算机”这个词。了解你的计算机执行一条指令要多长时间，从内存中取一个word要多长时间（包括缓存命中和未命中的情况），从磁盘上读取连续的数据要多长时间，定位到磁盘上的新位置又要多长时间。（）
- 尝试参与到一项语言标准化工作中。可以是ANSI C++委员会，也可以是决定自己团队的编码风格到底采用2个空格的缩进还是4个。不论是哪一种，你都可以学到在这门语言中到底人们喜欢些什么，他们有多喜欢，甚至有可能稍微了解为什么他们会有这样的感觉。
- 拥有尽快从语言标准化工作中抽身的良好判断力。
抱
着这些想法，我很怀疑从书上到底能学到多少东西。在我第一个孩子出生前，我读完了所有“怎样……”的书，却仍然感到自己是个茫无头绪的新手。30个月后，
我第二个孩子出生的时候，我重新拿起那些书来复习了吗？不。相反，我依靠我自己的经验，结果比专家写的几千页东西更有用更靠得住。
Fred Brooks在他的短文《》（没有银弹）中确立了如何发现杰出的软件设计者的三步规划：
- 尽早系统地识别出最好的设计者群体。
- 指派一个事业上的导师负责有潜质的对象的发展，小心地帮他保持职业生涯的履历。
- 让成长中的设计师们有机会互相影响，互相激励。
这实际上是假定了有些人本身就具有成为杰出设计师的必要潜质；要做的只是引导他们前进。说得更简洁：“每个人都可以被教授如何雕塑；而对米开朗基罗来说，能教给他的倒是怎样能够不去雕塑。杰出的程序员也一样”。
所以尽管去买那些Java书；你很可能会从中找到些用处。但你的生活，或者你作为程序员的真正的专业技术，并不会因此在24小时、24天甚至24个月内发生真正的变化。参考文献
Bloom, Benjamin (ed.) , Ballantine, 1985.
Brooks, Fred, , IEEE Computer, vol. 20, no. 4, 1987, p. 10-19.
Hayes, John R., , Lawrence Erlbaum, 1989.
Lave, Jean, , Cambridge University Press, 1988.
答案
各种操作的计时，2001年夏天在一台典型的1GHz PC上完成：
执行单条指令 1 纳秒 = (1/1,000,000,000) 秒
从L1缓存中取一个word 2 纳秒
从主内存中取一个word 10 纳秒
从连续的磁盘位置中取一个word 200 纳秒
从新的磁盘位置中取一个word（寻址） 8,000,000纳秒 = 8毫秒
脚注
T. Capey指出Amazon上面《》的页面中，《Teach Yourself Bengali in 21 days》和《Teach Yourself Grammar and Style》被列在了“购买此书的顾客还买了以下书籍”栏目里面。我猜其中一大部分察看这两本书的人都是从我这里过去的。
下面是英文原文：
Teach Yourself Programming in Ten Years
Peter Norvig
Why is everyone in such a rush?
Walk into any bookstore, and you'll see how to
Teach Yourself Java
in 7 Days alongside endless variations offering to teach Visual
Basic, Windows, the Internet, and so on in a few days or hours. I did
the following at :
and got back 248 hits. The first 78 were computer books (number 79
was ). I replaced "days" with
and got remarkably similar results: 253 more books, with 77 computer
books followed by at number 78. Out of
the top 200 total, 96% were computer books.
The conclusion is that either people are in a big rush to learn
about computers, or that computers are somehow fabulously easier to
learn than anything else. There are no books on how to learn
Beethoven, or Quantum Physics, or even Dog Grooming in a few days.
Let's analyze what a title like
could mean:
- Learn: In 3 days you won't have time to write several
significant programs, and learn from your successes and failures with
them. You won't have time to work with an experienced programmer and
understand what it is like to live in that environment. In short, you
won't have time to learn much. So they can only be talking about a
superficial familiarity, not a deep understanding. As Alexander Pope said,
a little learning is a dangerous thing.
- Pascal: In 3 days you might be able to learn the syntax of
Pascal (if you already knew a similar language), but you couldn't
learn much about how to use the syntax. In short, if you were, say, a
Basic programmer, you could learn to write programs in the style of
Basic using Pascal syntax, but you couldn't learn what Pascal is
actually good (and bad) for. So what's the point? once said: "A language that doesn't affect the way you
think about programming, is not worth knowing". One possible point is
that you have to learn a tiny bit of Pascal (or more likely, something
like Visual Basic or JavaScript) because you need to interface with an
existing tool to accomplish a specific task. But then you're not
learning how to program; you're learning to accomplish that task.
- in Three Days: Unfortunately, this is not enough, as the next
section shows.
Teach Yourself Programming in Ten Years
Researchers (, )
have shown it takes about ten years to develop expertise in any of a
wide variety of areas, including chess playing, music composition,
painting, piano playing, swimming, tennis, and research in
neuropsychology and topology. There appear to be no real shortcuts:
even Mozart, who was a musical prodigy at age 4, took 13 more years
before he began to produce world-class music. In another genre, the
Beatles seemed to burst onto the scene with a string of #1 hits and an
appearance on the Ed Sullivan show in 1964. But they had been playing
small clubs in Liverpool and Hamburg since 1957, and while they had
mass appeal early on, their first great critical success,
Sgt. Peppers, was released in 1967. Samuel Johnson thought it
took longer than ten years: "Excellence in any department can be
attained only by the labor of a lifetime; it is not to be purchased at
a lesser price." And Chaucer complained "the lyf so short, the craft
so long to lerne."
Here's my recipe for programming success:
- Get interested in programming, and do some because it is fun. Make sure
that it keeps being enough fun so that you will be willing to put in ten years.
- Talk to other programmers; read other programs. This is more important
than any book or training course.
- Program. The best kind of learning is . To put it more technically, "the maximal level of
performance for individuals in a given domain is not attained
automatically as a function of extended experience, but the level of
performance can be increased even by highly experienced individuals as
a result of deliberate efforts to improve."
and "the most effective learning requires a well-defined task with an
appropriate difficulty level for the particular individual,
informative feedback, and opportunities for repetition and corrections
of errors." (p. 20-21) The book
is an interesting
reference for this viewpoint.
- If you want, put in four years at a college (or more at a
graduate school). This will give you access to some jobs that require
credentials, and it will give you a deeper understanding of the field,
but if you don't enjoy school, you can (with some dedication) get
similar experience on the job. In any case, book learning alone won't
be enough. "Computer science education cannot make anybody an expert
programmer any more than studying brushes and pigment can make
somebody an expert painter" says Eric Raymond, author of The New
Hacker's Dictionary. One of the best programmers I ever hired had
only a High School degree; he's produced a lot of , has his own , and made enough in stock options to buy his own .
- Work on projects with other programmers. Be the best programmer
on some projects; be the worst on some others. When you're the best,
you get to test your abilities to lead a project, and to inspire
others with your vision. When you're the worst, you learn what the
masters do, and you learn what they don't like to do (because they
make you do it for them).
- Work on projects after other programmers. Be involved in
understanding a program written by someone else. See what it takes to
understand and fix it when the original programmers are not
around. Think about how to design your programs to make it easier for
those who will maintain it after you.
- Learn at least a half dozen programming languages. Include one
language that supports class abstractions (like Java or C++), one that
supports functional abstraction (like Lisp or ML), one
that supports syntactic abstraction (like Lisp), one
that supports declarative specifications (like Prolog or C++
templates), one that supports coroutines (like Icon or Scheme), and
one that supports parallelism (like Sisal).
- Remember that there is a "computer" in "computer science". Know
how long it takes your computer to execute an instruction, fetch a
word from memory (with and without a cache miss), read consecutive words from disk, and seek to a new location on disk. ()
- Get involved in a language
standardization effort. It could be the ANSI C++ committee, or it
could be deciding if your local coding style will have 2 or 4 space
indentation levels. Either way, you learn about what other people
like in a language, how deeply they feel so, and perhaps even a little
about why they feel so.
- Have the good sense to get off the language standardization effort as
quickly as possible.
With all that in mind, its questionable how far you can get just by
book learning. Before my first child was born, I read all the
How
To books, and still felt like a clueless novice. 30 Months later,
when my second child was due, did I go back to the books for a
refresher? No. Instead, I relied on my personal experience, which
turned out to be far more useful and reassuring
to me than the thousands of pages written
by experts.
Fred Brooks, in his essay
identified a three-part plan for finding great
software designers:
- Systematically identify top designers as early as possible.
- Assign a career mentor to be responsible for the development of the prospect and carefully keep a career file.
- Provide opportunities for growing designers to interact and stimulate each other.
This assumes that some people already have the qualities necessary for
being a great designer; the job is to properly coax them along. put it more succinctly: "Everyone can be taught to sculpt:
Michelangelo would have had to be taught how not to. So it is with the
great programmers".
So go ahead and buy that Java book; you'll probably get some use out of it.
But you won't change your life, or your real overall expertise as a
programmer in 24 hours, days, or even months.
References
Bloom, Benjamin (ed.) , Ballantine, 1985.
Brooks, Fred, , IEEE Computer, vol. 20, no. 4, 1987, p. 10-19.
Hayes, John R., Lawrence Erlbaum, 1989.
Lave, Jean, , Cambridge University Press, 1988.
Approximate timing for various operations on a typical 1GHz PC in summer 2001:
| execute single instruction | 1 nanosec = (1/1,000,000,000) sec
|
| fetch word from L1 cache memory | 2 nanosec
|
| fetch word from main memory | 10 nanosec
|
| fetch word from consecutive disk location | 200 nanosec
|
| fetch word from new disk location (seek) | 8,000,000 nanosec = 8 millisec
|
Appendix: Language Choice
Several people have asked what programming language they should learn first.
There is no one answer, but consider these points:
- Use your friends. When asked "what operating system should
I use, Windows, Unix, or Mac?", my answer is usually: "use whatever
your friends use." The advantage you get from learning from your
friends will offset any intrinsic difference between OS, or
between programming languages. Also consider your future friends:
the community of programmers that you will be a part of if you
continue. Does your chosen language have a large growing community
or a small dying one? Are there books, web sites, and online forums
to get answers from? Do you like the people in those forums?
- Keep it simple. Programming languages such as C++
and Java are designed for professional development by large teams of
experienced programmers who are concerned about the run-time efficiency of
their code.
As a result, these languages have complicated parts designed for these circumstances.
You're concerned with learning to program. You don't need that complication.
You want a language that was designed to be easy to learn and remember by a
single new programmer.
- Play. Which way would you rather learn to play the piano: the
normal, interactive way, in which you hear each note as soon as you hit a key,
or "batch" mode, in which you only hear the notes after you finish a whole song?
Clearly, interactive mode makes learning easier for the piano, and also for
programming. Insist on a language with an interactive mode and use it.
Given these criteria, my recommendations for a first programming
language would be
or
. But your
circumstances may vary, and there are other good choices. If your
age is a single-digit, you might prefer
or (older learners might also enjoy these). The important
thing is that you choose and get started.
Appendix: Books and Other Resources
Several people have asked what books and web pages they should learn
from. I repeat that "book learning alone won't be enough" but I can
recommend the following:
- Scheme: is
probably the best introduction to computer science, and it does
teach programming as a way of understanding the computer science.
You can see on this book, as well as the . The book is
challenging and will weed out some people who perhaps could be
successful with another approach.
- Scheme:
is one of the best books
on how to actually design programs in an elegant and functional way.
- Python:
is a good introduction using Python.
- Python: Several
online
are available at .
- Oz:
is seen by some as the modern-day successor to Abelson & Sussman.
It is a tour through the big ideas of programming, covering a wider
range than Abelson & Sussman while being perhaps easier to read and
follow. It uses a language, Oz, that is not widely known but serves as
a basis for learning other languages.
Notes
T. Capey points out that the page on Amazon now has the "Teach Yourself
Bengali in 21 days" and "Teach Yourself Grammar and Style" books under the
"Customers who shopped for this item also shopped for these items"
section. I guess that a large portion of the people who look at that
book are coming from this page.
