傳世之文《Teach Yourself Programming in Ten Years》十年學會程式設計
作為一個正在努力的程式設計師看了這篇文章之後思考了非常多，雖然是很久之前的文章了，所使用的技術也已經不斷地革新，但是文章背後所傳遞的思想真的非常深刻而有建設性。學習程式設計真的不是21天24hours的事情，我也特別討厭周圍或者網路上的人報了一個班學了一些知識就在那裡裝大牛，其實內裡一點都經不起推敲。希望有志之士可以看看這篇傳世之文，你一定會有所收穫的。
原文：http://norvig.com/21-days.html
譯文：http://daiyuwen.freeshell.org/gb/misc/21-days-cn.html
目錄
英文版 Teach Yourself Programming in Ten Years
Why is everyone in such a rush?
Teach Yourself Programming in Ten Years
So You Want to be a Programmer
Appendix: Books and Other Resources
中文版 十年學會程式設計
為何人人都這麼著急？
信步走進任何一家書店，你會看到名為《如何在7天內學會Java》的書，還有各 種各樣類似的書： 在幾天內或幾小時內學會Visual Basic, Windows, Internet等等，一眼望不到 盡頭。我在Amazon 上做了如下的 強力檢索 ：
pubdate: after 1992 and title: days and (title: learn or title: teach yourself)
得到了248個結果。前78個都是計算機類書籍（第79個是
結論是：要麼人們都在急急忙忙地學習計算機，要麼計算機比其它任何東西都 容易學。沒有書籍教你在幾天內學會古典音樂、量子物理，或者是養狗。
讓我們分析一下，象一本名為《三天內學會Pascal》的書意味著什麼：
- 學習： 在三天裡，你沒有時間寫一些重大的程式，並從成功或失敗中 得益。你沒有時間與有經驗的程式設計師合作，並理解在那樣的環境下工作是怎麼回 事。一句話，你不會有時間學到太多東西。因此他們只能談論一些膚淺的東西，而 不是深入的理解。正如亞力山大教皇所說，淺嘗輒止是危險的事情。
- Pascal： 在三天時間裡，你可能學會Pascal的語法（如果你 已經學過類似的語言），但你學不到更多的如何使用這些語法的知識。也就是說， 假如你曾是個BASIC程式設計師，你可以學著用Pascal語法寫出BASIC風格的程式，但你不 可能瞭解Pascal真正的好處（和壞處）。那麼關鍵是什麼？Alan Perlis 說過：“一種不改變你程式設計的思維方式的語言，不值得去學。” 一種可 能的情況是：你必須學一點兒Pascal（或可能性更大的象Visual Basic 或 JavaScript之類），因為你為了完成某種特定的任務，需要與一個現存的工具建立 介面。不過那不是學習如何程式設計，而是在學習如何完成那個任務。
- 三天內： 很不幸，這不夠，原因由下一節告訴我們。
在十年裡學會程式設計
研究表明 (Hayes，Bloom)在 任何一種領域內，象下棋、作曲、繪畫、鋼琴演奏、游泳、網球、以及原子物理學和拓 撲學，等等，要達到專家水平大約都要化十年時間。沒有真正的捷徑：即使是莫扎 特，4歲時就是音樂神童，13年後才開始寫出世界級的作品。在另一方面，披頭 士似乎在1964年的Ed Sullivan表演上一炮走紅。但他們從1957年就開始表演，在 獲得大眾青睞後，他們的第一個重大成功，Sgt. Peppers，是1967年發 行的。Samuel Johnson （塞繆爾·約翰遜，英國辭典編纂家及作家）認為要花比十年更長的時間：“在任何領域中出類拔萃都 要用畢生的勞作來取得；它不可能用較低的代價獲得。” 而Chaucer（喬叟，英 國詩人）感嘆到：“人生短暫，學海無涯。”
這是我為程式設計成功開出的方子：
- 設法對程式設計感興趣，並且因為它有趣而編一些程式。確保程式設計一直充滿足夠 樂趣，這樣你才願意投入十年寶貴時間。
- 與其他程式設計師交流； 閱讀其它程式。這比任何書本或訓練課程都 重要。
- 寫程式。 最好的學習方式是 從實 踐中學習。 用更技術性的話說，“在一個給定的領域內，個人的最大能力不 是自動地由擴充套件了的經驗取得的，但即使是高度有經驗的人也可以通過有意識的 努力來提高自己的能力” (p. 366) 和 “最有效的學習需要因人而異的適當難度，目標明確的任務，豐富的資訊反 饋，以及重複的機會和錯誤修正。” (p. 20-21) 此書 Cognition in Practice: Mind，Mathematics，and Culture in Everyday Life是闡明此觀點的令人感興趣的參考文獻。
- 如果願意，在大學裡呆上4年或更長（在研究生院裡）。你會接觸到 一些需要學歷證明的工作，你會對此領域有更深的理解。如果你不喜歡學校， 你可以（通過一 些貢獻）在工作中獲得相似的經驗。在任何情況下，光啃書本是不夠的。Eric Raymond，The New Hacker's Dictionary一書的作者，說過，“電腦科學不能把任何人變成程式設計 專家，就象光研究刷子和顏料不會使人變成畫家一樣。” 我僱傭過的最好的程式設計師 之一僅有高中程度；他做出了許多優秀的 軟體，有他自己的新聞組， 而且通過股票期權，他無疑比我富有的多。
- 和其他程式設計師一起做專案。在其中的一些專案中作為最好的程式 員； 而在另一些專案中是最差的。當你是最好的，你能測試領導專案的能力，用你 的觀點激發別人。當你是最差的，你學習傑出者是怎麼做的，瞭解他們不喜歡做 什麼（因為他們吩咐你做事）。
- 在其他程式設計師 之後接手專案。使自己理解別人寫的程式。 當程式的原作者不在的時候，研究什麼需要理解並且修改它。思考如何設計你的 程式以便後來者的維護。
- 學習至少半打的程式語言。包括一種支援類抽象的語言（象Java 或C++），一種支援函式化抽象的語言（象Lisp或ML），一種支援語法抽象的語 言（象 Lisp），一種支援宣告規格說明的語言（象Prolog或C++ 的模板），一種支援 共行程式（coroutine）的語言（象Icon或Scheme），一種支援並行的語言（象Sisal）。
- 請記住“電腦科學”中有“計算機”一詞。瞭解你的計算機要花多 長時間執行一條指令，從記憶體中取一個字（有cache），從磁碟中讀取連續的字， 和在磁碟中找到新的位置。（答案）
- 參與一種語言標準化的工作。它可以是ANSI C++委員會， 也可以是決定你周圍小範圍內的程式設計風格是應該兩個還是四個空格縮排。通 過任何一種方式，你瞭解到其他人在某種語言中的想法，他們的理解深度，甚至一 些他們這樣想的原因。
- 找到適當的理由儘快地從語言標準化的努力中脫身。
明白了這些，僅從書本中你能得到多少就成了一個問題。在我第一個孩子出生前， 我讀了所有的（關於育兒的）How to 書籍，仍然感覺是個手足無措的新手。30個月以後，我 的第二個孩子快要出生了，我回頭溫習這些書了嗎？ 沒有。相反，我依靠我的個人 經驗，它比專家寫的數千頁書更有用和可靠。
Fred Brooks在他的隨筆 《沒有銀彈》 中定出了一個尋找優秀軟體設計者的三步計劃：
- 儘可能早地，有系統地識別頂級的設計人員。
- 為設計人員指派一位職業導師，負責他們技術方面的成長，仔細地為他們規劃 職業生涯。
- 為成長中的設計人員提供相互交流和學習的機會。
此計劃假設某些人已經具備了傑出設計者的必要才能； 要做的只是如何恰當地誘 導他們。 Alan Perlis 說得更簡明扼要：“每個人都能被教會雕刻：對米開朗其羅而言， 反倒是告訴他哪些事不要做。同樣的道理也適用於優秀的程式設計師。”
所以儘管買那本Java的書吧。你可能會從中學到點兒東西。但作為一個程式設計師，你不會在 幾天內或24小時內，哪怕是幾個月內改變你的人生，或你實際的水平。
參考文獻
Bloom, Benjamin (ed.) Developing Talent in Young People, Ballantine, 1985.
Brooks, Fred, No Silver Bullets, IEEE Computer, vol. 20, no. 4, 1987, p. 10-19.
Hayes, John R., Complete Problem Solver Lawrence Erlbaum, 1989.
Lave, Jean, Cognition in Practice: Mind, Mathematics, and Culture in Everyday Life, Cambridge University Press, 1988.
答案
2001年夏天典型的1GHz PC的各種操作要花的時間
| 執行一條指令 | 1 nsec = (1/1,000,000,000) sec |
| 從L1 cache memory 中取一個字 | 2 nsec |
| 從記憶體中取一個字 | 10 nsec |
| 從磁碟的連續位置取一個字 | 200 nsec |
| 從磁碟的新位置取一個字(seek) | 8,000,000nsec = 8msec |
附錄：語言的選擇
不少人問我，他們首先該學哪種程式語言。沒有絕對的答案，不過請考慮以下幾 點：
- 用你的朋友的。當被問起“我該用哪種作業系統，Windows，Unix， 還是Mac？”，我總是回答：“你朋友用什麼，你就用什麼。” 你從朋友那能學 到知識，這種優勢可以抵銷不同作業系統或語言之間本質的差異。也考慮你將來 的朋友：程式設計師社群 — 你將成為它的一部分如果你繼續往前走的話。你選擇的 語言是否有一個成長中的社群，還是人數不多、即將消亡？ 有沒有書籍、網站、 線上論壇回答你的問題？ 你喜歡論壇裡的那些人嗎？
- Keep it simple, stupid. 象C++和Java這樣的語言是為經驗豐富的 程式設計師組成的團隊進行專業開發而設計的，他們專注於程式碼執行時的效率。因此， 這些語言有些部分非常複雜。 而你關注的是如何程式設計，不需要那些複雜性。你 需要的是這樣的語言： 對單個的程式設計新手來說，它易學易記。
- 練習。你偏愛哪種學彈鋼琴的方式：通常的互動式的方式，你一 按下琴鍵就能聽到音符；還是“批量”模式，你只有彈完整首曲子才能聽到音符？ 顯然，用互動模式學習彈鋼琴更容易些，程式設計也一樣。堅持用互動模式學習並使 用一種語言。
有了上面的準則，我推薦的第一個程式語言是Python或Scheme。因人而異，還有其它 好的選擇。如果你的年紀是10歲以下，你可能更喜歡Alice。關鍵是你要選擇並開始實踐。
附錄：書籍和其它資源
不少人問我，他們該從什麼書籍或網頁開始學起。我重申“僅從書本里學習是不 夠的。” 但我還是推薦：
- Scheme: Structure and Interpretation of Computer Programs (Abelson & Sussman)可能是最好 的電腦科學的入門書，而且它的確把講授程式設計作為理解電腦科學的一種方法。 但它具有挑戰性，會讓許多通過其它方式可能成功的人望而卻步。
- Scheme: How to Design Programs (Felleisen et al.)是關於如何用一種優美的、函式化的方式設 計程式的最好的書之一。
- Python: Python Programming: An Intro to CS (Zelle)是優秀的Python入門指導。
- Python: Python.org上有許多線上指導。
- Oz: Concepts, Techniques, and Models of Computer Programming (Van Roy & Haridi) 被視為Abelson & Sussman的當代繼承者。它是對程式設計的高層次概念的巡視。 涉及的範圍比Abelson & Sussman更廣，同時可能更容易學習和跟進。 它用了叫 做Oz的語言，不太知名，卻可以作為學習其它語言的基礎。
腳註
This page also available in Japanese translation thanks to Yasushi Murakawa, in Spanish translation thanks to Carlos Rueda and in German translation thanks to Stefan Ram.
T. Capey points out that the Complete Problem Solver 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.
英文版 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 24 Hours alongside endless variations offering to teach C, SQL, Ruby, Algorithms, and so on in a few days or hours. The Amazon advanced search for [title: teach, yourself, hours, since: 2000 and found 512 such books. Of the top ten, nine are programming books (the other is about bookkeeping). Similar results come from replacing "teach yourself" with "learn" or "hours" with "days."
The conclusion is that either people are in a big rush to learn about programming, or that programming is somehow fabulously easier to learn than anything else. Felleisen et al. give a nod to this trend in their book How to Design Programs, when they say "Bad programming is easy. Idiots can learn it in 21 days, even if they are dummies." The Abtruse Goose comic also had their take.
Let's analyze what a title like Teach Yourself C++ in 24 Hours could mean:
- Teach Yourself: In 24 hours 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 a C++ environment. In short, you won't have time to learn much. So the book can only be talking about a superficial familiarity, not a deep understanding. As Alexander Pope said, a little learning is a dangerous thing.
- C++: In 24 hours you might be able to learn some of the syntax of C++ (if you already know another language), but you couldn't learn much about how to use the language. In short, if you were, say, a Basic programmer, you could learn to write programs in the style of Basic using C++ syntax, but you couldn't learn what C++ is actually good (and bad) for. So what's the point? Alan Perlis 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 C++ (or more likely, something like JavaScript or Processing) 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 24 Hours: Unfortunately, this is not enough, as the next section shows.
Teach Yourself Programming in Ten Years
Researchers (Bloom (1985), Bryan & Harter (1899), Hayes (1989), Simmon & Chase (1973)) have shown it takes about ten years to develop expertise in any of a wide variety of areas, including chess playing, music composition, telegraph operation, painting, piano playing, swimming, tennis, and research in neuropsychology and topology. The key is deliberative practice: not just doing it again and again, but challenging yourself with a task that is just beyond your current ability, trying it, analyzing your performance while and after doing it, and correcting any mistakes. Then repeat. And repeat again. 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.
Malcolm Gladwell has popularized the idea, although he concentrates on 10,000 hours, not 10 years. Henri Cartier-Bresson (1908-2004) had another metric: "Your first 10,000 photographs are your worst." (He didn't anticipate that with digital cameras, some people can reach that mark in a week.) True expertise may take a lifetime: Samuel Johnson (1709-1784) said "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 (1340-1400) complained "the lyf so short, the craft so long to lerne." Hippocrates (c. 400BC) is known for the excerpt "ars longa, vita brevis", which is part of the longer quotation "Ars longa, vita brevis, occasio praeceps, experimentum periculosum, iudicium difficile", which in English renders as "Life is short, [the] craft long, opportunity fleeting, experiment treacherous, judgment difficult." Of course, no single number can be the final answer: it doesn't seem reasonable to assume that all skills (e.g., programming, chess playing, checkers playing, and music playing) could all require exactly the same amount of time to master, nor that all people will take exactly the same amount of time. As Prof. K. Anders Ericssonputs it, "In most domains it's remarkable how much time even the most talented individuals need in order to reach the highest levels of performance. The 10,000 hour number just gives you a sense that we're talking years of 10 to 20 hours a week which those who some people would argue are the most innately talented individuals still need to get to the highest level."
So You Want to be a Programmer
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 your ten years/10,000 hours.
- Program. The best kind of learning is learning by doing. 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." (p. 366) 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 Cognition in Practice: Mind, Mathematics, and Culture in Everyday Life is an interesting reference for this viewpoint.
- Talk with other programmers; read other programs. This is more important than any book or training course.
- 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 your own or 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 great software, has his own news group, and made enough in stock options to buy his own nightclub.
- 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. Understand 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 them after you.
- Learn at least a half dozen programming languages. Include one language that emphasizes class abstractions (like Java or C++), one that emphasizes functional abstraction (like Lisp or ML or Haskell), one that supports syntactic abstraction (like Lisp), one that supports declarative specifications (like Prolog or C++ templates), and one that emphasizes parallelism (like Clojure or Go).
- 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. (Answers here.)
- 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 No Silver Bullet 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. Alan Perlis 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". Perlis is saying that the greats have some internal quality that transcends their training. But where does the quality come from? Is it innate? Or do they develop it through diligence? As Auguste Gusteau (the fictional chef inRatatouille) puts it, "anyone can cook, but only the fearless can be great." I think of it more as willingness to devote a large portion of one's life to deliberative practice. But maybe fearless is a way to summarize that. Or, as Gusteau's critic, Anton Ego, says: "Not everyone can become a great artist, but a great artist can come from anywhere."
So go ahead and buy that Java/Ruby/Javascript/PHP 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 or 21 days. How about working hard to continually improve over 24 months? Well, now you're starting to get somewhere...
References
Bloom, Benjamin (ed.) Developing Talent in Young People, Ballantine, 1985.
Brooks, Fred, No Silver Bullets, IEEE Computer, vol. 20, no. 4, 1987, p. 10-19.
Hayes, John R., Complete Problem Solver Lawrence Erlbaum, 1989.
Chase, William G. & Simon, Herbert A. "Perception in Chess" Cognitive Psychology, 1973, 4, 55-81.
Lave, Jean, Cognition in Practice: Mind, Mathematics, and Culture in Everyday Life, Cambridge University Press, 1988.
Answers
Approximate timing for various operations on a typical PC:
| execute typical instruction | 1/1,000,000,000 sec = 1 nanosec |
| fetch from L1 cache memory | 0.5 nanosec |
| branch misprediction | 5 nanosec |
| fetch from L2 cache memory | 7 nanosec |
| Mutex lock/unlock | 25 nanosec |
| fetch from main memory | 100 nanosec |
| send 2K bytes over 1Gbps network | 20,000 nanosec |
| read 1MB sequentially from memory | 250,000 nanosec |
| fetch from new disk location (seek) | 8,000,000 nanosec |
| read 1MB sequentially from disk | 20,000,000 nanosec |
| send packet US to Europe and back | 150 milliseconds = 150,000,000 nanosec |
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 Python or Scheme. Another choice is Javascript, not because it is perfectly well-designed for beginners, but because there are so many online tutorials for it, such as Khan Academy's tutorial. But your circumstances may vary, and there are other good choices. If your age is a single-digit, you might prefer Alice or Squeak or Blockly (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: Structure and Interpretation of Computer Programs (Abelson & Sussman) is probably the best introduction to computer science, and it does teach programming as a way of understanding the computer science. You can see online videos of lectures on this book, as well as the complete text online. The book is challenging and will weed out some people who perhaps could be successful with another approach.
- Scheme: How to Design Programs (Felleisen et al.) is one of the best books on how to actually design programs in an elegant and functional way.
- Python: Python Programming: An Intro to CS (Zelle) is a good introduction using Python.
- Python: Several online tutorials are available at Python.org.
- Oz: Concepts, Techniques, and Models of Computer Programming (Van Roy & Haridi) 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 Complete Problem Solver 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. Thanks to Ross Cohen for help with Hippocrates.