Structure And Interpretation Of Computer Programs Quotes

Programs must be written for people to read, and only incidentally for machines to execute.

Syntactic sugar causes cancer of the semicolon.

Computational processes are abstract beings that inhabit computers. As they evolve, processes manipulate other abstract things called data. The evolution of a process is directed by a pattern of rules called a program. People create programs to direct processes. In effect, we conjure the spirits of the computer with our spells.

It is better to have 100 functions operate on one data structure than 10 functions on 10 data structures.

If art interprets our dreams, the computer executes them in the guise of programs!

Underlying our approach to this subject is our conviction that "computer science" is not a science and that its significance has little to do with computers. The computer revolution is a revolution in the way we think and in the way we express what we think. The essence of this change is the emergence of what might best be called procedural epistemology—the study of the structure of knowledge from an imperative point of view, as opposed to the more declarative point of view taken by classical mathematical subjects. Mathematics provides a framework for dealing precisely with notions of "what is". Computation provides a framework for dealing precisely with notions of "how to".

It is possible, indeed important, to be able to separate these two notions—to create procedures without naming them, and to give names to procedures that have already been created.

A powerful programming language is more than just a means for instructing a computer to perform tasks. The language also serves as a framework within which we organize our ideas about processes. Thus, when we describe a language, we should pay particular attention to the means that the language provides for combining simple ideas to form more complex ideas. Every powerful language has three mechanisms for accomplishing this: - primitive expressions, which represent the simplest entities the language is concerned with, - means of combination, by which compound elements are built from simpler ones, and - means of abstraction, by which compound elements can be named and manipulated as units.

I hope the field of computer science never loses its sense of fun. ... What you know about computing other people will learn. Don’t feel as if the key to successful computing is only in your hands. What’s in your hands I think and hope is intelligence: the ability to see the machine as more than when you were first led up to it, that you can make it more.

In testing primality of very large numbers chosen at random, the chance of stumbling upon a value that fools the Fermat test is less than the chance that cosmic radiation will cause the computer to make an error in carrying out a "correct" algorithm. Considering an algorithm to be inadequate for the first reason but not for the second illustrates the difference between mathematics and engineering.

I think that it's extraordinarily important that we in computer science keep fun in computing. When it started out, it was an awful lot of fun. Of course, the paying customers got shafted every now and then, and after a while we began to take their complaints seriously. We began to feel as if we really were responsible for the successful, error-free perfect use of these machines. I don't think we are. I think we're responsible for stretching them, setting them off in new directions, and keeping fun in the house. I hope the field of computer science never loses its sense of fun. Above all, I hope we don't become missionaries. Don't feel as if you're Bible salesmen. The world has too many of those already. What you know about computing other people will learn. Don't feel as if the key to successful computing is only in your hands. What's in your hands, I think and hope, is intelligence: the ability to see the machine as more than when you were first led up to it, that you can make it more.

We are about to study the idea of a computational process. Computational processes are abstract beings that inhabit computers. As they evolve, processes manipulate other abstract things called data. The evolution of a process is directed by a pattern of rules called a program. People create programs to direct processes. In effect, we conjure the spirits of the computer with our spells. A computational process is indeed much like a sorcerer's idea of a spirit. It cannot be seen or touched. It is not composed of matter at all. However, it is very real. It can perform intellectual work. It can answer questions. It can affect the world by disbursing money at a bank or by controlling a robot arm in a factory. The programs we use to conjure processes are like a sorcerer's spells. They are carefully composed from symbolic expressions in arcane and esoteric programming languages that prescribe the tasks we want our processes to perform. A computational process, in a correctly working computer, executes programs precisely and accurately. Thus, like the sorcerer's apprentice, novice programmers must learn to understand and to anticipate the consequences of their conjuring. Even small errors (usually called bugs or glitches) in programs can have complex and unanticipated consequences.

The computational paradigm for the universe supplements the ordinary mechanistic paradigm: the universe is not just a machine, it is a machine that processes information. The universe computes. The computing universe is not a metaphor, but a mathematical fact: the universe is a physical system that can be programmed at its most microscopic level to perform universal digital computation. Moreover, the universe is not just a computer: it is a quantum computer. Quantum mechanics is constantly injecting fresh, random bits into the universe. Because of its computational nature, the universe processes and interprets those bits, naturally giving rise to all sorts of complex order and structure (Lloyd, 2006).

Web Application Development In this modern world of computer technology all people are using internet. In particular, to take advantage of this scenario the web provides a way for marketers to get to know the people visiting their sites and start communicating with them. One way of doing this is asking web visitors to subscribe to newsletters, to submit an application form when requesting information on products or provide details to customize their browsing experience when next visiting a particular website. In computing, a web application is a client–server software application in which the client runs in a web browser. HTML5 introduced explicit language support for making applications that are loaded as web pages, but can store data locally and continue to function while offline. Web Applications are dynamic web sites combined with server side programming which provide functionalities such as interacting with users, connecting to back-end databases, and generating results to browsers. Examples of Web Applications are Online Banking, Social Networking, Online Reservations, eCommerce / Shopping Cart Applications, Interactive Games, Online Training, Online Polls, Blogs, Online Forums, Content Management Systems, etc.. Applications are usually broken into logical chunks called “tiers”, where every tier is assigned a role. Traditional applications consist only of 1 tier, which resides on the client machine, but web applications lend themselves to an n-tiered approach by nature. Though many variations are possible, the most common structure is the three-tiered application. In its most common form, the three tiers are called presentation, application and storage, in this order. A web browser is the first tier (presentation), an engine using some dynamic Web content technology (such as ASP, CGI, ColdFusion, Dart, JSP/Java, Node.js, PHP, Python or Ruby on Rails) is the middle tier (application logic), and a database is the third tier (storage).The web browser sends requests to the middle tier, which services them by making queries and updates against the database and generates a user interface. Client Side Scripting / Coding – Client Side Scripting is the type of code that is executed or interpreted by browsers. Client Side Scripting is generally viewable by any visitor to a site (from the view menu click on “View Source” to view the source code). Below are some common Client Side Scripting technologies: HTML (HyperTextMarkup Language) CSS (Cascading Style Sheets) JavaScript Ajax (Asynchronous JavaScript and XML) jQuery (JavaScript Framework Library – commonly used in Ajax development) MooTools (JavaScript Framework Library – commonly used in Ajax development) Dojo Toolkit (JavaScript Framework Library – commonly used in Ajax development) Server Side Scripting / Coding – Server Side Scripting is the type of code that is executed or interpreted by the web server. Server Side Scripting is not viewable or accessible by any visitor or general public. Below are the common Server Side Scripting technologies: PHP (very common Server Side Scripting language – Linux / Unix based Open Source – free redistribution, usually combines with MySQL database) Zend Framework (PHP’s Object Oriented Web Application Framework) ASP (Microsoft Web Server (IIS) Scripting language) ASP.NET (Microsoft’s Web Application Framework – successor of ASP) ColdFusion (Adobe’s Web Application Framework) Ruby on Rails (Ruby programming’s Web Application Framework – free redistribution) Perl (general purpose high-level programming language and Server Side Scripting Language – free redistribution – lost its popularity to PHP) Python (general purpose high-level programming language and Server Side Scripting language – free redistribution). We also provide Training in various Computer Languages. TRIRID provide quality Web Application Development Services. Call us @ 8980010210

economic engineering, the prices of commodities are shocked, and the public consumer reaction is monitored. The resulting echoes of the economic shock are interpreted theoretically by computers and the psycho-economic structure of the economy is thus discovered.

Seibel: What's your desert-island list of books for programmers? Peyton Jones: Well, you should definitely read Jon Bentley's Programming Pearls. Speaking of pearls, Brian Hayes has a lovely chapter in this book Beautiful Code entitled, “Writing Programs for ‘The Book’” where I think by “The Book” he means a program that will have eternal beauty. You've got two points and a third point and you have to find which side of the line between the two points this third point is on. And several solutions don't work very well. But then there's a very simple solution that just does it right. Of course, Don Knuth's series, The Art of Computer Programming. I don't think it was ever anything I read straight through; it's not that kind of book. I certainly referred to it a lot at one stage. Chris Okasaki's book Purely Functional Data Structures. Fantastic. It's like Arthur Norman's course only spread out to a whole book. It's about how you can do queues and lookup tables and heaps without any side effects but with good complexity bounds. Really, really nice book. Everyone should read this. It's also quite short and accessible as well. Structure and Interpretation of Computer Programs. Abelson and Sussman. I loved that. And Compiling with Continuations, Andrew Appel's book about how to compile a functional program using continuation passing style. Also wonderful. Books that were important to me but I haven't read for a long time: A Discipline of Programming by Dijkstra. Dijkstra is very careful about writing beautiful programs. These ones are completely imperative but they have the “Hoare property” of rather than having no obvious bugs they obviously have no bugs. And it gives very nice, elegant reasoning to reason about it. That's a book that introduced me for the first time to reasoning about programs in a pretty watertight way. Another book that at the time made a huge impression on me was Per Brinch Hansen's book about writing concurrent operating systems. I read it lots of times.

Memory has been discussed here as though it consisted mainly of a body of data. But experts possess skills as well as knowledge. They acquire not only the ability to recognize situations or to provide information about them; they also acquire powerful special skills for dealing with situations as they encounter them. Physicians prescribe and operate as well as diagnose. The boundary between knowledge and skill is subtle. For example, when we write a computer program in any language except machine language, we are really not writing down processes but data structures. These data structures are then interpreted or compiled into processes that is, into machine-language instructions that the computer can understand and execute. Nevertheless for most purposes it is convenient for us simply to ignore the translation step and to treat the computer programs in higher-level languages as representing processes.

I often said I wouldn't have pursued programming as a career if I still did drugs. This is probably true, since weed was always immensely crippling for me. I would have weed hangovers for days, and while stoned, was unable to read or do much of anything besides clean and play video games. Whether or not this would have turned out to be true is academic, but it's definitely true that I wouldn't have become a programmer if I hadn't lost my mind, because the recovery process taught me my most valuable skill as a programmer: how to not think. Programming requires the acceptance that you are entering meaningless symbols into a machine that's going to spit out other meaningless symbols, and this can be hard to accept. It requires abandoning all hope for an answer for the existential "why?" in favour of shuffling boolean values ad infinitum. By no interpretation of the concept of understanding does a computer understand what you're telling it or what it's telling you. On top of that, programming as an act is more often hindered than helped by thinking. Despite zero years of training in computer science, I've found I have an edge in debugging because I never look or ask for an explanation. Ninety percent of the computer bugs in a program are tiny, one-line errors, and you just have to find that error. Holding the entire logical structure of a million lines of code in your mind in futile. The task is to find the references and connections and track them back until you hit the problem. If I get an error message, I copy it into Google, because someone somewhere has encountered and solved the problem, probably by tracking down the people who originally wrote the program. In seven years of programming, I've solved exactly two undocumented bugs via pure deductive reasoning.

Since large programs grow from small ones, it is crucial that we develop an arsenal of standard program structures of whose correctness we have become sure—we call them idioms—and learn to combine them into larger structures using organizational techniques of proven value.

Every reader should ask himself periodically ``Toward what end, toward what end?'' -- but do not ask it too often lest you pass up the fun of programming for the constipation of bittersweet philosophy.