What Is JavaScript?

What Is JavaScript?

           JavaScript is an interpreted(rather than compiled) object-oriented programming  language
that has been developed for use alongside other Web tools. JavaScript does not operate as
a standalone language. It is designed to work together with HTML for creating interactive
Web pages. It is not the same as Java, which is a compiled object-oriented language.
JavaScript is used to write client side applications, which means that JavaScript code
is sent to a user’s computer when a Web page is loaded. The code is then executed, basi-cally line by line, by a JavaScript interpreter included as part of the user’s (client’s) Web
browser. This arrangement minimizes security issues that can arise when a client computer
interacts with the computer that sent the page. It also makes it easy to package an entire
problem, with its own user interface and solution, self-contained within a single document.
But the inability to interact dynamically with information stored on a serverimposes limi-tations on the kinds of tasks that JavaScript can accomplish. 


         It is commonplace to refer to any set of written computer instructions as a “program.”
However, this term is more rigorously applied to a separate entity that can be executed on its
own. Because JavaScript is interpreted rather than compiled, a separately executable entity is
never created. Instead, JavaScript code statements are interpreted and executed one at a time,
essentially “on the fly.” Although this may seem inefficient, there is rarely any discernible
time lag associated with executing JavaScript commands on modern computers.
JavaScript is one of a class of scripting languages whose purpose is to access and mod-ify components of an existing information interface. (Microsoft’s VBScript is another
scripting language.) In this case, the interface is an HTML document. As soon as HTML
documents on the Web evolved from one-way delivery systems for displaying fixed con-tent, something like JavaScript immediately became necessary. One of its first applications
arose from the need to check values entered by users into the fields of HTML forms that
can be sent back to the originator. (Forms are discussed in a later chapter.) JavaScript can
be used to compare input values against an expected range or set of values and to generate
appropriate messages and other actions based on those comparisons.

       JavaScript has evolved into a complete programming language with extensive capabili-ties for manipulating text and handling mathematical operations, useful for a wide range of
computing problems. Possible applications include many self-contained scientific and
engineering calculations. As noted earlier, JavaScript is restricted to problems that do not
need to access external data sources, regardless of whether those sources reside on a local
computer or on a remote server.

What is css?

What is css?

          Cascading Style Sheets, fondly referred to as CSS, is a simple design language intended to simplify
the process of making web pages presentable. Put simply, CSS handles the look and feelpart of a
web page. With CSS, you can control the color of the text, the style of fonts, the spacing between
paragraphs, how columns are sized and laid out, what background images or colors are used, as
well as a variety of other effects.

CSS was created in language that is easy to learn and understand, but it provides powerful control
over the presentation of a document. Most commonly, CSS is combined with the markup languages
HTML or XHTML. These markup languages contain the actual text you see in a web page — the
paragraphs, headings, lists, and tables — and are the glue of a web document. They contain the
web page’s data, as well as the CSS document that contains information about what the web page
should look like.

HTML and XHTML are very similar languages. In fact, for the majority of documents today, they
are pretty much identical, although XHTML has some stricter requirements about the type of syn-tax used.

Html introduction

Html introduction

                    HTML stands for Hypertext Markup Language. And the fascinating thing about HTML is that it is based on a simple text file. It isn’t magic—it’s hypertext markup. The markup tags tell your browser how to display the page. 

It seems that the Internet world changes completely every few years. We are on the brink of change now. Since the early 1990s, HTML has evolved through several language specifications. The last HTML specification, HTML 4.01, allowed you to use both uppercase and lowercase tags. The next generation of HTML is XHTML, which stands for Extensible Hypertext Markup Language. The first XHTML spec, XHTML 1.0, was recommended as a standard by the W3C World Wide Web Consortium in 2000.

Perl programing language

Perl programing language

            Perl is a very high-level programming language originally developed in the 1980s by Larry Wall. Perl is now being developed by a group of individuals known as the Perl5-Porters under the watchful eye of Larry. One of Perl's many strengths is its ability to process arbitrary chunks of textual data, known as strings , in many powerful ways, including regular-expression string manipulation. This capability makes Perl an excellent choice for database programming, since the majority of information stored within databases is textual in nature. Perl takes the pain of manipulating strings out of programming, unlike C, which is not well-suited for that task. Perl scripts tend to be far smaller than equivalent C programs and are generally portable to other operating systems that run Perl with little or no modification.

Perl also now features the ability to dynamically load external modules , which are pieces of software that can be slotted into Perl to extend and enhance its functionality. There are literally hundreds of these modules available now, ranging from mathematical modules to three-dimensional graphics-rendering modules to modules that allow you to interact with networks and network software. The DBI is a set of modules for Perl that allows you to interact with databases.

In recent years, Perl has become a standard within many companies by just being immensely useful for many different applications, the "Swiss army knife of programming languages." It has been heavily used by system administrators who like its flexibility and usefulness for almost any job they can think of. When used in conjunction with DBI, Perl makes loading and dumping databases very straightforward, and its excellent data-manipulation capabilities allow developers to create and manipulate data easily.