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3. ASCII CODE and more

Occasionally we'll study some rather technical stuff, particularly if it comes up over and over again in the "computer world." This is one of those days. If you want to be comfortable in technical circles, then you can't be scared when you hear things like "the ASCII 7-bit character set (ISO 646)" or when you see things like "–" showing up in HTML code. This brings us to...


ASCII (3a)

What is "ASCII"? "ASCII" stands for "American Standard Code for Information Interchange"; it is the standard character set for most computer operating systems. It has 27 = 128 characters, numbered 0 through 127. The first 32 characters (numbered 0 through 31) are obscure: ASCII was designed for use with teletypes, and many of these first characters were for that use. The remaining 96 characters are the printing characters available on a standard English keyboard.

What's "ISO 646"? The ASCII character set was standardized by ISO (the International Standards Organization) as ISO-646.

What's the connection between ASCII and HTML? The HTML file that you create consists only of characters from the ASCII character set. For example, there's no accented "e" in the ASCII character set, so you'll never see an accented "e" when you look through any HTML file. (Of course, after the browser "interprets" the HTML file, then you can certainly see an accented "e"!)


Are all ASCII characters treated the same way in an HTML file? Most characters in your HTML file show up on your web page about the same way they look in your HTML file. (Type the symbol "$" in your HTML file, and you'll see a "$" on the corresponding web page.) But some characters (like < and >) have special uses: when your browser sees these special characters (in a certain context) in your HTML file, it "escapes" from its normal mode and does something different. (Characters that have special meaning like this are sometimes referred to as "escape characters.")
How do I get special characters to appear on my web page? There are extended character sets with loads of special symbols. For example, to get entry #169 in the ISO-Latin-1 character set (which is the copyright symbol,  © ), you would type "&#169;" in your HTML document. The "&" symbol is an escape character that tells your browser that a "character code" comes next. The semicolon at the end says you're done: sometimes it can be omitted, but it never hurts to put it there to be safe. Some (but not all) commonly-used symbols have names in addition to their numbers, to make them easier to refer to. For example, to get the "Ñ" symbol, you could type either "&#209;" or "&Ntilde;".

Printable version of Index Card 3a

Printable version of Index Card 3b



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