Special Characters

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Special Characters

Back in issue 3 I introduced the use of Special Characters in your HTML code. If you don't recall, special characters are a code sequence used in HTML in order to print characters that are either not available directly through the keyboard or which may be confused as HTML control characters by the Browser. Examples of the former include the Copyright ©, Trademark ™ and Registration ® symbols. Examples of the latter include almost any character not in the alphabet. Symbols such as <>&? may play havoc with your web page if you simply try to use them as is.

You can define special characters and symbols in your HTML document with a simple code that is started by an & (ampersand)and terminated by a ; (semicolon). The code for the copyright symbol © is © the Trademark symbol ™ is ™ and the Registration symbol ® ® I posted a complete set at www.IMSWebTips.com/is22fig1.htm.

These special codes are important for every HTML author to know. A common mistake new Web Designers make is to simply enter special characters into their HTML document whenever they are needed. After all, they are located right there on your keyboard. You may be lucky and get away with it. If the browser can interpret the code however, it may produce strange results. How for example can you display the HTML command <BODY> on your web page? This is obviously an HTML tag that a Browser will interpret. The solution is to use the ampersand commands to display the < and > symbols as in: <BODY>

When I covered this topic in issue 3 I promised to create a table of the extended ASCII characters.

What are ASCII characters?

The ASCII characters are used on most computers (EBCDIC is used on IBM Mainframes). An ASCII character is an 8 bit byte used to represent 1 of 256 characters. When you hit a key on your keyboard for instance, you are entering a byte that represents the key you typed. If you count your keys you will see that there are far fewer than 256, even when you include the use of the shift key. This is because the primary keys are represented by the first 7 bits which give you 128 combinations. Of these 128, many characters are non printable while others simply do not have a key to represent them.

So what are all the extra characters used for?

Codes 0 - 32 are control characters. 13 is a carriage return.
Codes 33 - 47 are symbols such as # $ % *
Codes 48 - 57 are the ten digits (0 - 9)
Codes 58 - 64 more symbols < > ?
Codes 65 - 90 UPEER CASE ALPHABET
Codes 91 - 96 more symbols [ ^
Codes 97 - 122 lower case alphabet
Codes 123 - 126 more symbols {}~
Code 127 the Delete Key
Codes 128 - 255 the extended character set

In many text editors you can enter almost any character by pressing the Alt key while typing the three digit ASCII value into the keypad at the right of most keyboards. To add the letter A for instance, hold the ALT key and enter 065. Although this is a tedious way to enter the standard keys, it is a very simple way to access the extended character set in a text editor. It is NOT the correct way to enter them into a HTML document. This is because your text editor may not support the Extended character set or because the characters may be Interpreted.

The correct way to enter special character codes into an HTML document is through the use of the & tag with the four digit ASCII code preceded by a pound (#) symbol. The letter A would then be entered as A

So what special characters are included in the extended character set?

I have included a table of the entire extended character set at: www.IMSWebtips.com/is22fig3.htm. For your reference, I have also included that standard character set at www.IMSWebtips.com/is22fig2.htm

Note that a rectangular box is not a symbol. It means the character isnot printable and should be avoided.

One other thing to keep in mind, the ASCII character set is language specific. A visitor to your site will see the characters that are defined by their language. Since most web sites are designed for a specific language, this should not present a problem.

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"IMS Web Tips" ISSN 1488-7088
© Copyright 2001 Virtual Mechanics
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"IMS Web Tips" is a weekly news letter for all web site managers regardless of experience who are looking for detailed information on creating, maintaining and promoting their web sites.

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