Below are a few of the scripting and programming languages that we
use to create our web application and websites.
Perl
Perl is an interpreted scripting language with extensive facilities for data manipulation and rapid application development. Perl is basically block-structured, but also supports object-oriented programming. "Perl" stands for "Practical Extraction and Reporting Language," a reference to the purpose for which the Perl interpreter was originally created: system administration and data reduction. Perl has gone through several major evolutionary phases. The current language version is Perl5, but some pockets of Perl4 use still exist. Perl5 is backward-compatible with 4. In the feature list below, features that are specific to Perl5 are marked with an asterisk. data types: strings, numbers, lists, associative arrays, references, globs data types: objects
* conventional math and arithmetic functions subroutines, variable argument lists dynamic memory handling with garbage collection extensive file I/O facilities extensive system interface support regular expression pattern matching and substitution very extensive data output formatting capabilities various loops and conditional constructs object definition and inheritance
* separable namespaces (packages)
* lexical and dynamic scope local variables
* on-the-fly code evaluation and error handling
The Perl language does not support the traditional notion of records or structs. Instead, associative arrays (hashes) are provided to serve all such purposes. Similarly, Perl supports object-oriented programming, but does not stipulate an object storage format. In Perl5, code is parsed and compiled into very high-level bytecodes prior to interpreted execution. This approach, and extensive optimization of the Perl interpreter and run-time engine, allow Perl scripts to achieve very high performance. Perl currently does not support multi-threading, although efforts are underway to add this important feature. Perl is very popular in the UNIX community, and gaining acceptance in the Microsoft Windows developer community. There is only one Perl language system; written in C to be very portable, it runs on all UNIX platforms, 32-bit Windows, VMS, and many other systems. Perl is free. Books, tutorials, and on-line resources for Perl are widely available, and generally of good quality. Add-on modules and pre-built scripts for Perl are also widely available, with more being written all the time. Add-ons for Perl are so numerous and in such wide demand that an organized replicated archive system for them exists: the Comprehensive Perl Archive Network (CPAN). There is no international standard for Perl syntax. The language definition is informally set forth in Programming Perl, 2nd Edition, by Wall, Christiansen, and Schwartz.
PHP
PHP is an interpreted server-side scripting language for web servers. It was designed to support simple, fast server-side extension for web development. The syntax of PHP is fairly simple, and very similar to that of Perl, with some aspects of Bourne shell, Javascript, and C . Variables in PHP are weakly types, the language does not support strong typing. PHP supports the a modest complement of primitive data types: integers, floats, and strings. It also supports heterogenous multi-dimensional associative arrays, with very convenient syntax. PHP offers some object-oriented functionality, allowing the programmer to define classes with member variables and methods, and to use simple inheritance. The language includes an extensive set of operators and built-in functions for manipulating strings, numbers, and arrays. Control structures supported in PHP include simple conditionals, plus several kinds of bounded and unbounded loops. PHP does not support any kind of module or library structure, but it does permit simple file inclusion (similar to C's #include directive). In addition to its basic web functionality, PHP is supported by extensive libraries that provide database interfaces and interaction with many common web data formats. There is only one implementation of series of PHP implementations, as of late 1999 the current version was 3.0, with 4.0 in beta. PHP is free, distributed as source code, and runs on Unix, Linux, and Windows.
JavaScript
JavaScript is a loosely typed scripting language with object-oriented and block-structuring features. Invented by Netscape Communications for adding dynamic behavior to web pages, JavaScript was originally called 'LiveScript'. The syntax of JavaScript is similar to that of C or Java, but simpler and not as rich. Primitive data types include integers, reals, strings, and a associative arrays. Javascript is loosely typed, any variable can contain data of any type, and conversion is mostly automatic. The language definition includes extensive facilities for controlling and manipulating parts of web pages, especially HTML forms. Each version of Netscape Navigator has brought a new version of JavaScript, and later versions also include a complicated security model for restricting the hostile capabilities of scripts embedded in web pages. Microsoft web browser also support Javascript, but under the name "JScript".
CGI
The Common Gateway Interface (CGI) is a standard for interfacing external applications with information servers, such as HTTP or Web servers. A plain HTML document that the Web daemon retrieves is static, which means it exists in a constant state: a text file that doesn't change. A CGI program, on the other hand, is executed in real-time, so that it can output dynamic information.
For example, let's say that you wanted to "hook up" your Unix database to the World Wide Web, to allow people from all over the world to query it. Basically, you need to create a CGI program that the Web daemon will execute to transmit information to the database engine, and receive the results back again and display them to the client. This is an example of a gateway, and this is where CGI, currently version 1.1, got its origins.
The database example is a simple idea, but most of the time rather difficult to implement. There really is no limit as to what you can hook up to the Web. The only thing you need to remember is that whatever your CGI program does, it should not take too long to process. Otherwise, the user will just be staring at their browser waiting for something to happen.
Ajax
Ajax, shorthand for "Asynchronous JavaScript and XML", is a web development technique for creating interactive web applications. The intent is to make web pages feel more responsive by exchanging small amounts of data with the server behind the scenes, so that the entire web page does not have to be reloaded each time the user requests a change. This is intended to increase the web page's interactivity, speed, and usability.
MySQL
MySQL is a multithreaded, multi-user SQL database management system (DBMS) which has, according to MySQL AB, more than 10 million installations.
MySQL is owned and sponsored by a single for-profit firm, the Swedish company MySQL AB, which holds the copyright to most of the codebase. This is similar to the JBoss model and how the Free Software Foundation handles copyright in its projects, and dissimilar to how the Apache project does it, where the software is developed by a public community and the copyright to the codebase is owned by its individual authors.
The company develops and maintains the system, selling support and service contracts, as well as proprietary-licensed copies of MySQL, and employing people all over the world who collaborate via the Internet. MySQL AB was founded by David Axmark, Allan Larsson, and Michael "Monty" Widenius. The CEO is Mårten Mickos.
The MySQL company also sells another DBMS, MaxDB, which is from an unrelated codebase.
HTML
HTML, short for HyperText Markup Language, is the predominant markup language for the creation of web pages. It provides a means to describe the structure of text-based information in a document — by denoting certain text as headings, paragraphs, lists, and so on — and to supplement that text with interactive forms, embedded images, and other objects. HTML is written in the form of labels (known as tags), surrounded by less-than (<) and greater-than signs (>). HTML can also describe, to some degree, the appearance and semantics of a document, and can include embedded scripting language code which can affect the behavior of web browsers and other HTML processors.
HTML is also often used to refer to content of the MIME type text/html or even more broadly as a generic term for HTML whether in its XML-descended form (such as XHTML 1.0 and later) or its form descended directly from SGML (such as HTML 4.01 and earlier).
DHTML
Dynamic HTML or DHTML is a collection of technologies used together to create interactive and animated web sites by using a combination of a static markup language (such as HTML), a client-side scripting language (such as JavaScript), a presentation definition language (Cascading Style Sheets, CSS), and a Document Object Model.
A DHTML webpage is any webpage in which client-side scripting changes variables of the presentation definition language, which in turn affects the look and function of otherwise "static" HTML page content, after the page has been fully loaded and during the viewing process. Thus the dynamic characteristic of DHTML is the way it functions while a page is viewed, not in its ability to generate a unique page with each page load.
By contrast, a "dynamic web page" is a broader concept — any web page generated differently for each user, load occurrence, or specific variable values. This includes pages created by client side scripting, and ones created by server-side scripting (such as PHP or Perl) where the web server generates content before sending it to the client.
XML
The Extensible Markup Language (XML) is a W3C-recommended general-purpose markup language. The XML recommendation specifies both the structure of XML, and the requirements for XML processors. XML is considered "general-purpose" because it enables anyone to originate and use a markup language for many types of applications and problem domains. Numerous formally defined markup languages are based on XML, such as RSS, MathML, GraphML, XHTML, Scalable Vector Graphics, MusicXML, and thousands of others.
XML's primary purpose is to facilitate the sharing of data across different information systems, particularly systems connected via the Internet. It is a simplified subset of Standard Generalized Markup Language (SGML), and is designed to be relatively human-legible.
Java
Java is a simple, portable object-oriented language designed by research staff at Sun Microsystems. The feel of the Java language is fairly similar to that of C++, but it also borrows ideas from Modula-3, Mesa, and Objective-C. The feature set of Java is fairly broad: it has inheritance, strong type checking, modularity (packages), exception handling, polymorphism, concurrency, dynamic loading of libraries, arrays, string handling, garbage collection, and a pretty extensive standard library. The newest version of the language, Java 1.2 (aka Java Platform 2), includes nested classes, persistence, and reflection as well as many additional standard libraries. The fundamental structural component of a Java program is the class. All data and methods in Java are associated with some class, there is no 'global' data or functions as in C++. Classes can be members of packages; package and class membership help determine scope and visibility of data and methods. Java does not include features that its designers felt would compromise the similicity or safety of the language, so Java has no true pointers, no true multiple inheritance, no operator overloading, and no macro preprocessor. The lack of multiple inheritance could have been a serious shortcoming, but Java does support the definition and interitance of multiple stateless "interfaces", which serve for most areas where multiple inheritance might be desired. Java also has no facility for generic functions, but since the language imposes a rooted class hierarchy (all object classes inherit from the root class 'Object'), any need for generics is greatly reduced. Java 1.1 added powerful reflection and object class manipulation capabilities, and uses these to support object serialization I/O. The Java standard library packages include extensive I/O facilities, a comprehensive GUI toolkit, collection classes, date/time support, cryptographic security classes, distributed computation support, and system interfaces. Java is typically compiled to platform-independent byte-codes. These byte-codes must be interpreted by a Java Virtual Machine (JVM), which may choose to compile the byte-codes further into native machine instructions. There is a strict definition of the Java byte-code file format, the .class file format, which ensures portability of compiled Java classes. In additional to normal application development, Java is used to develop embedded programs, called 'applets', for web browsers and other Java-enabled platforms. This capability is an important part of Java, and the standard library packages include a security manager to restrict the capabilities of Java applets. These applet facilities were important to Java's widespread adoption and popularity. Commercial Java compilers and development environments are readily available; among the most popular are products from Symantec and Microsoft. Javasoft supports and distributes a 'reference' Java implementation known as the JDK, it is free.
