| Delivering the pieces� |
| Protocol | |
| Language | |
| Tools |
| HTTP � HyperText Transfer Protocol | ||
| who else?� Tim Berners-Lee | ||
| when you type a URL or click on a hyperlink, such as http://www.somewhere.domain, | ||
| your PC uses the HTTP protocol to communicate with the Web server that has the pages you want to fetch | ||
| HTTP � HyperText Transfer Protocol | |
| At the moment, this is the dominant protocol for PC-to-server communication on the Web, but browsers are fully capable of using other protocols, e.g., | |
| FTP � File Transfer Protocol | |
| (file = .doc, .txt, .jpg, .wav, .htm, .html�) |
| HTML � HyperText Markup Language | ||
| This is TB-L�s great invention! | ||
| It tells your browser (IE, Netscape�) how to display the file that your PC retrieves (using HTTP) from the Web server. | ||
| It is a subset of SGML, Standardized General Markup Language� | ||
| What is a �markup language�? | |
| It is a metalanguage, a language for talking about languages | |
| The simplest markup language is the set of standard proofreader�s marks | |
| �http://www.m-w.com/mw/table/proofrea.htm |
| The simplest markup language is the set of standard proofreader�s marks | |
| �I wroteabout this painting beecause tranquility it shows.� | |
| This tells you what you should have written. |
| HTML � HyperText Markup Language | ||
| HTML is analogous to the red pencil marks on a corrected paper or manuscript | ||
| It tells the browser how the author of the Web page wants it to appear inside the window � text, images, multimedia, everything (well, almost everything�) | ||
| HTML � HyperText Markup Language | ||
| A Web page is simply �text� | ||
| It is created by typing according to certain rules | ||
| It can be created in a simple text editor (like Windows� Notepad) or a word processor or with an HTML editor | ||
| The best:� HTML Kit (chami.com) | ||
| HTML � HyperText Markup Language | |||
| Text � �Web pages� � that is organized according to HTML has a very simple structure and a small number of rules | |||
| structure = grammar (parts of speech) | |||
| rules = vocabulary (words) | |||
| Both of these � structure and rules � are specified with �tags.� | |||
| HTML � HyperText Markup Language | ||||
| Structure � the parts of a Web page | ||||
| opening declaration: <html> | ||||
| This is a �tag,� and it says �Here there be HTML.� | ||||
| HTML � HyperText Markup Language | |||
| Structure � the parts of a Web page | |||
| opening declaration: <html> | |||
| open first part:� <head> | |||
| close first part: </head> | |||
| open second part:� <body> | |||
| close second part:� </body> | |||
| closing declaration:� </html> | |||
| A file with these lines would create a Web page: | |
| <html> | |
| <head> | |
| </head> | |
| <body> | |
| </body> | |
| </html> | |
| An empty page, of course, but still a Web page� |
| What else would we need?� Two things� | |
| <html> | |
| <head> | |
| <title>My Web page</title> | |
| <meta> info about the page, e.g., keywords | |
| </head> | |
| <body> | |
| stuff, content, text, images� | |
| </body> | |
| </html> |
| In addition to these four tags (and their closures) � <html>, <head>, <title>, and <body> � there are a few others that are essential and that provide the �rules�: | |
| <a> � �anchor,� the hyperlink | |
| <img> � image | |
| Each of these contains and conveys additional information through �attributes� that are inside the tag� |
| <a> � �anchor,� the hyperlink | |
| On the ISP100 course Web page, there is a link to the file containing the class schedule: | |
| <a href=�s07schedule.htm">Class schedule</a> | |
| href=�� is an attribute of the <a> tag | |
| the info inside the �� is the URL of the linked Web page | |
| �http://hawk.albany.edu/isp100/s07schedule.htm� | |
| <img> � image | |
| This is the tag, and some of its possible attributes, that inserts the green arrow: | |
| <img src="4logo6.gif" width="31" height="46" hspace="10" vspace="10" border="0" align="left"> | |
| These attributes control size, position, etc., of the image on the page. |
| In total, about 90 tags (and their attributes) exist to control aspects of Web page design: | |
| <font> | |
| <center> | |
| <table>, <tr>,<td> | |
| <b>, <i> | |
| <br>, <p> | |
| <frame> | |
| <applet>, <script> | |
| These last two lead us to Tools� |
| An HTML file, e.g., s07schedule.htm: | ||
| always contains instructions to the browser for displaying the page | ||
| may contain two kinds of �programs�: | ||
| Java applets, e.g., the IP address application at the top of the ISP100 course Web page | ||
| Javascripts, e.g., �mouseover� effects or popups | ||