lecture 1: markup

Web pages are just data files, like Word documents or spreadsheets. When you surf the WWW, you download these web pages using applications known as browsers. We will look at these on the next slide.

Browsers do not actually render the page "as is", however. Web pages are actually written using a series of instructions that are known as HTML. This stands for HyperText Markup Language. Remember that web pages are transmitted from one computer to another. The more information that has to be transmitted, the slower the connection will be. It is more efficient to apply formatting at the receiver's end, rather than at the originator's. So that is what HTML is - a set of instructions that tell the reader's computer how to display the page.

A real-world analogy is with punctuation. These two sentences have the same text, but different meanings:

    The student said the lecturer was an idiot.

    "The student", said the lecturer, "was an idiot".

The quotation marks " " enclose the quoted passages of text. By doing so, they change our interpretation of the sentence.

We do similar things with other marks, like ? marks, which is even clearer in Spanish:

    ¿Que?

Web pages are written in "plain text". Plain text is just the 255 characters of ASCII code, and cannot alone be used to distinguish between things as simple as italic and non-italic text, let alone place images, colours and so on onto the web page. These formatting tasks are done by the mark-up; by the HTML, in other words. So just as the "Que" above is marked up as a question by placing symbols (instructions) at the start and end, so a piece of italicised text also has instructions at the start and end. These say to the browser, "start rendering this text as italic" and "return to normal".

Therefore, in the same way that we interpret plain text differently depending on the punctuation marks around it, so browsers interpret plain text differently depending on the mark-up instructions around it.

All mark-up instructions like this are known as tags. By the end of this lecture we will have built a web page using simple tags. First, though, we will look a bit more closely at the tools you need to both display and design web pages. These are browsers and editors respectively.