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A database is a structured collection of records or data that is stored in a computer system. The structure is achieved by organizing the data according to a database model. The model in most common use today is the relational model. Other models such as the hierarchical model and the network model use a more explicit representation of relationships

increase their speed

common kind of index is a sorted list of the contents of some particular table column, with pointers to the row associated with the value

Dynamic programming problems are to be solved with tabular methods

breadth-first search

Memorize the value of pi You should always try to remember the value of pi as far as possible, 3.1415926535897932384626433832795, certainly the part in italics. The judges may not give the value in the question, and if you use values like 22/7 or 3.1416 or 3.142857, then it is very likely that some of the critical judge inputs will cause you to get the wrong answer. You can also get the value of pi as a compiler-defined constant or from the following code: Pi=2*acos(0)

The Common Gateway Interface (CGI) is a standard protocol for interfacing external application software with an information server, commonly a web server. The task of such an information server is to respond to requests (in the case of web servers, requests from client web browsers) by returning output. Each time a request is received, the server analyzes what the request asks for, and returns the appropriate output. The two basic methods for the server to do this are the following: If the request identifies a file stored on disk, then return the contents of that file. If the request identifies an executable command and possibly arguments, then run the command and return its output. CGI defines a standard way of doing the second. It defines how information about the server and the request is passed to the command in the form of arguments and environment variables, and how the command can pass back extra information about the output (such as the type) in the form of headers.

n mathematics, a ternary relation or triadic relation is a finitary relation in which the number of places in the relation is three. Ternary relations may also be referred to as 3-adic, 3-ary, 3-dimensional, or 3-place. Just as a binary relation is formally defined as a set of pairs, i.e. a subset of the Cartesian product A × B of some sets A and B, so a ternary relation is a set of triples, forming a subset of the Cartesian product A × B × C of three sets A, B and C.

In computing, a Uniform Resource Identifier (URI) consists of a string of characters used to identify or name a resource on the Internet. Such identification enables interaction with representations of the resource over a network (typically the World Wide Web) using specific protocols. Schemes specifying a specific syntax and associated protocols define each URI. Contents [hide]

A Uniform Resource Name (URN) functions like a person's name, while a Uniform Resource Locator (URL) resembles that person's street address. The URN defines an item's identity, while the URL provides a method for finding it. The ISBN system for uniquely identifying books provides a typical example of the use of typical URNs. ISBN 0486275574 (urn:isbn:0-486-27557-4) cites unambiguously a specific edition of Shakespeare's play Romeo and Juliet. In order to gain access to this object and read the book, one would need its location: a URL address. A typical URL for this book on a unix-like operating system might look like the file path file:///home/username/RomeoAndJuliet.pdf, identifying the electronic book saved in a local hard disk. So URNs and URLs have complementary purposes.

Model–view–controller (MVC) is an architectural pattern used in software engineering. Successful use of the pattern isolates business logic from user interface considerations, resulting in an application where it is easier to modify either the visual appearance of the application or the underlying business rules without affecting the other. In MVC, the model represents the information (the data) of the application; the view corresponds to elements of the user interface such as text, checkbox items, and so forth; and the controller manages the communication of data and the business rules used to manipulate the data to and from the model.

MVC is often seen in web applications, where the view is the actual HTML or XHTML page, and the controller is the code that gathers dynamic data and generates the content within the HTML or XHTML. Finally, the model is represented by the actual content, which is often stored in a database or in XML nodes, and the business rules that transform that content based on user actions.