In almost all the industries (factories), a large number of machines are run by mechanical power. The problem of transmitting this mechanical power from one shaft (driving shaft) to another shaft (driven shaft) has invented certain devices of transmission of power.

For example in a bicycle, the power at the shaft of paddles is transmitted to the rear wheel. In a motor cycle, the power developed in the engine is transmitted to the rear wheel. In fact in all the machines, the power developed in an engine is transmitted to some suitable part where it is used to do the mechanical work.

TRANSMISSION OF POWER

The technique of transferring mechanical power from one shaft to another with the help of various means is called Transmission of Power. In this process mechanical power is transmitted from one shaft to another shaft.

Generally, in factories the power from one shaft to another shaft is transmitted by means of the following modes :

• Belts and Ropes
• Chains
• Gears
• Clutches

Three of the above mentioned modes of transmission of power, i.e. belts, chains and gears are used when the power is to be transferred between parallel shafts.

Clutches are used when the power transmission is to take place between collinear and co - axial shafts.

Classification of belts

The general classification of the belts used for transmission of power depends upon the following:

1. The cross section of the belt.
2. The material used in the construction of the belt.

(1) Depending upon the cross section, the belts can have the following classification:

(a) Flat Belts

(b) Vee Belts

(c) Circular Belts

(2) Depending upon the material used for the construction of the belt, the Belts can be classified as

(i) Leather Belts

(ii) Cotton Belts

(iii) Rubber Belts

(iv) Metallic Belts

(v) Steel Belts

Belts and Ropes

Flat Belts - Flat Belts are used for moderate transmission of power between the two shafts when the distance between the two shafts is not more than 10 m.

Vee Belts - Wherever large amount of power is to be transmitted between the two parallel shafts, Vee belt and grooved pulley system is used. This is used when the distance between the two shafts is very small.

Ropes or Circular Belts - Wherever a large amount of power is to be transferred from one shaft to another when the distance is not more than 5 m. ropes or circular belts are used.

Chains

Wherever exactly same power is to be transmitted from one shaft to another one without any slip, a chain drive is used. This mode of transmission of power is suitable for large distances.

Gears

Wherever the power transmission is to take place between two parallel shafts very near to each other but the amount of power to be transmitted is very very large without any slip, gears are used.

Clutches

Whenever a large amount of power is to be transmitted from one shaft to another shaft and the two shafts are collinear and co-axial, the clutches are used.

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 INTRODUCTION

The World Wide Web is the most unique service of the internet. Its protocols allow it to transmit text and multimedia file. formats to users while also allowing web browsers to access another internet services. The web is based on a concept called hypertext, which means that text within the paragraph on a web page, is designed to act as link to other web pages and the web pages are written in a special language called HTML. HTML stands for Hypertext Markup Language.

Internet is an integral part of all of us today. The World Wide Web bring loads of information on variety of pages called the web pages. A web page is generally a single HTML document, which might include text, graphics, sound file and hypertext links. Each HTML document you create is a single web page, regardless of the length of the document or the amount of information included. 

HTML is simple enough that typical computer user can generate HTML document without the benefit of a special application.

HTML lets you to design and create web pages that can be read on any type of computer. Using any web browser software, you can be connected to the web.

HISTORY OF HTML

HTML was first proposed in 1989, it took shape as a subset of SGML (Standard Generalized Markup Language), which is a higher level markup language that has long been a favourite of the department of defense and many other organizations with a truly large volume of document to manage. Like HTML it describes formatting and hypertext links and define different components of a document.HTML definitely the simpler of the two and although they are related. Because HTML can transmit over the internet (in the form of web pages) it is much simpler than SGML. SGML is not exactly ideal for transmission access to the internet to many different types of computer, user and browser application. HTML is more suited to this task. 

HTML is not a programming language., but a markup language.

HTML (HYPERTEXT MARKUP LANGUAGE)

Hypertext Markup Language (HTML) is a cross-platform standard. The same HTML document can be viewed using browsers on Windows, Macintosh and UNIX platforms. This is possible because HTML conforms to a specification or a standard, defined by the International Organization for Standardization (ISO). The ISO is an international body comprised of computer manufacturers, software vendors, university researchers and members of industry and government.

｢Definition Byte

Markup refers to a sequence of characters or other symbols that are inserted in a text document. They indicate how a document should be structured.

Hypertext Markup Language (HTML) is a language used to develop Web pages.｣

HTML is a language used to create documents using tags that determine the structure and format. Hypertext provides a way to organize and present information. Its purpose is to link documents in a non-linear manner.

｢Definition Byte

Hypermedia: Multimedia data types incorporated into HTML documents.｣

Hypertext documents contain active links or pointer to other information sources. A user can click a link and advance to a specific hypertext document section or go to a different Web document altogether.

You are probably familiar with some common hypertext systems. Many computer Help systems, such as the one in Microsoft Word, include hypertext interfaces. Typically, a user will search and retrieve a document by typing in a keyword. He or she can then select other active links within the new document to find associated information. Active links usually have a visual distinction, such as underscored text or a pointer of some kind. 

The World Wide Web is responsible for hypertext′s rapid growth. Because of their intuitive nature, hypertext systems are widely used for navigating and exploring information.

｢Information Byte

Cross-platform software works on more than one type of system.｣

With hypertext, the information is text. Hypermedia is an extension of hypertext and it includes images, video, audio, animation and other multimedia data types which can be incorporated into HTML documents. The Web can be accurately described as a hypermedia system.

Ted Nelson first conceived hypertext in 1965. The first widely commercialized hypertext product was Hypercard, conceived by Bill Atkinson and introduced by Apple Computer in 1987. It incorporated many hypertext and hypermedia concept, but wat a proprietary system that worked only on Macintosh computers.

In contrast, HTML is a cross-platform language that works on Windows. Macintosh and UNIX platforms. Also, HTML and the Web are client/server system, whereas Hypercard works only on a stand alone Macintosh computer.

Markup Language

Markup language such as HTML is very different from programming languages because HTML does no act on external data: rather, the data and markup tags are both part of a single HTML document. Also HTML does not provide data structures or internal logic as procedural programming languages, such as a C or Pascal.

HTML has evolved from other languages. First, it was called as General Markup Language (GML). It originated at IBM In the late 1960s at a way to move formatted documents across different compute platforms. GML became the Standard Generalized Markup Language (SGML) in 1986 when the International Standards Organization defined it as a standard (ISO 8879). While SGML is a powerful markup language, it is also very complex and difficult to learn.

HTML language is a subset of SGML. Although it has fewer tags than SGML. It is easier to use and has become the standard method of encoding information for Web documents. As with GML, HTML Facilitates data exchange via a common document format across different types of computer systems and networks on the Web.

Limitations of HTML

HTML is not a programming language and is a simple text file. Therefore, complex designing cannot be accomplished. Heavy interactive forms or dynamic pages are a challenge to create using HTML. On the other hand languages like ASP(Active Server Pages). ASP Java Servers work wonders in creating dynamic pages.

Also Read ‒

What is XML?

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INTRODUCTION

The Extensible Markup Language (XML) is the universal format for structured documents and data on the Web. - W3C XML Web site. 2000-07-06.

The Extensible Markup Language (XML) is descriptively identified within the XML 1.0 W3C Recommendation as a particularly simple dialect [or subset'] of SGML" the goal of which is to enable generic SGML to be served, received, and processed on the net within the way that's now possible with HTML" that reason "XML has been designed for simple implementation, and for interoperability with both SGML and HTML". 

Note that the "HTML" referenced in the preceding sentence (bis) means HTML 4.0 and 3.2 which were in common use as of 10-February 1998. When the XML 1.0 specification was published as a W3C Recommendation. The next version of "HTML is predicted to be reformulated as an XML application, in order that it'll be based upon XML instead of upon SGML. As of December 1998. "Voyager was the W3C code name for HTML reformulated as an application of XML.

WHAT IS XML?

EXtensible Markup Language (XML) may be a thanks to apply structure to an internet page. XML provides a typical open format and mechanisms for structuring a document in order that it are often exchanged and manipulated.

If you are familiar with HyperText Markup Language (HTML) it will be easier to learn that XML. In fact, XML complements your HTML knowledge by allowing you to structure your data by "marking-up" the text and data to define the info content. 

Like HTML, XML uses tags to "markup" data content. Unlike HTML. in XML you define your own tags that meet the precise needs of your document. The custom tags make your data easier to arrange and search.

XML will not change the way of your web page look, but it will change the way the documents are ead and the way the documents are filed and stored.

MARKUP LANGUAGE

Markup gives meaning to a document. This is something you do everyday like highlighted text, check marks on a bank statement, etc. If we would like others to know what markup means, we'd like a group of rules to declare what constitutes markup and declaring exactly what it means,

A markup language is not a formatting language. It is also not a programming language because programming language creates a set of instruction that is interpreted into a program.

Information Byte

XML is subset of SGML. Other examples of Markup languages are: HTML, MathML. Latex.

A markup language is just a set of rules, In SGML, for example, anything in angle brackets is considered markup. <...>

The makers of HTML used SGML to form a group of rules declaring what markup in HTML means. This set of rules is contained during a separate document called the HTML DTD (Document Type Definition). HTML DTD. for example, says that when you come across the in a document start a new paragraph.

MARKUP DELIMITERS

The part of XML: element tags are as follows: 

Consider the following example:

Symbol         -         Description

<                   -      Start tag open delimiter

</                 -      End tag open delimiter

foo                -     Element name

>                   -      Tag close delimiter

/>                 -      Empty tag close delimiter

It is worth remembering that, whereas HTML simply relies on recognizing pre-programmed tag XML is triggered by these specific parts of the element tag and the XML processors behavior and what it expects to see next are directly controlled by the name symbols.

EVOLUTION OF XML

XML (Extensible Markup Language) is a simple and flexible markup language. It improves on the HTML approach.

A huge amount of information is lost when data is converted into HTML. If this information can be preserved then it can be used to build a whole New World of more information. XML is all about preserving useful information on the web.

Information Byte

The XML requires Internet Explorer 5.0 and above browsers to display is result. This browser on the XML built in parser. There are two types of parsers, one that only checks for the well-formed document, which is known as non-validating parser and the other is known as validating parser. The validating parser will check whether an XML document is well formed as well as the validation of DTDs. The latest browser by Netscape, i.e., Netscape 6.0, supports XML.

XML is a markup language that can run on any platform, operating system, or environment and is designed to provide developers with a mechanism to describe their content better.

It allows developers to write their own document type definition (DTD) that describe sets of tags and attributes that can be used to describe specific kind of content. DTDs are markup languages rulebooks that define what markup elements can be used to describe a document. If one wants to create one's own tags then we first need to define the tag in the DTD.

XML is a flexible framework. It enables to create one's own customized markup languages. All XML based languages will share the same look and feel. They will all share a common basic syntax. After this the developer is free to build his/her own diverse markup languages. 

Most of the XML-based markup languages are already a part of market today. For example, the Channel Definition Format (CDF). Electronic Commerce uses the Open Trading Protocol (OTP) and MML (Mathematical Markup Language) provides formatting for the mathematical equations.

XML has a definite advantage over HTML. HTML has a fixed set of predefined tags from which a page developer can choose and create his/her own page. On the other hand, XML does not define any particular set of tags. It provides a standardized framework with which one can define own tags and his/her needs.

RULES FOR XML

XML was developed since content specialists and designers realized that HTML is simply too limited scope to handle many tasks. It is not always simple to describe all content as paragraph, lists, tables and forms of HTML. The following points below list why XML is better than HTML.

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XML is a meta-language (ie can be used create new languages).

• Programs that process XML documents are easy to create and can be easily understood by all. However, to understand HTML one needs to have knowledge of its specific tags.

• The rules of an XML document are logical and simple. The XML syntax is easy to learn and utilize.

• The design of XML is formal. flexible and concise.

• XML checks for syntactical errors and the errors are mostly listed on the XML page. On the other hand. HTML lacks syntactical checking.

• The XML tag is case sensitive. For example, the tag <Myself> has a different effect than the tag <myself>. The beginning and ending tags must be the same.

• XML is particular on the aspect of the elements and their nested structure. HTML lacks structure, for instance the heading tags (H1 to H6) of HTML can be in any order. The browser is not particular about the order in which the heading tags are used.

XML files are documented in notepad and are saved with XML extension.

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