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Frequently Used Symbols in Web Development

Non-Standard Symbols Supplement Pages

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[ Non-Standard html codes (127 - 159) ] [ Non-Standard ("Extended") ASCII Codes (128 - 255) ]

Various symbols, although not technically a part of the defined HTML character sets, will print in some -- or most -- browsers. The underlying problem in their lack of printing uniformity is that many of these characters came into use through the DOS operating system as part of the ASCII standard or through Microsoft and the Windows operating system.

Although in fairly wide use, there are a number of problems with using these characters. One is that they may or may not render in any particular browser; particularly problematic are operating systems other than MS Windows, such as UNIX, where Windows-defined characters probably will not exist. A second problem is that these characters are non-SGML characters, which means that any page using them will not validate.

For the MS Windows based characters, they are specifically defnined in the operating system, not in HTML. This probably shows a general lack of planning and coordination among the various user and application development interests, but what else is new when dealing with Microsoft?

While there are legitimate uses for the standard ASCII character set (0 - 127) -- such as in URIs, where it may be safer to specify a character by the ASCII code than to print it outright -- the extended codes are another matter. These extended ASCII codes have an even murkier history than the non-standard HTML codes, dating back to the DOS days and a plethora of odds and ends added to the OS. While the Windows characters, non-SGML though they may be, pretty much display uniformly (when they do display), the extended ASCII codes are far more volitle (even in a non-HTML environment).

Most, if not all, of these symbols have corresponding definitions in the HTML standards, so it is just a legacy practice to use the non-standard definitions.

Because some of these symbols will not validate, they are listed separately on non-validated pages (except for the symbols themselves, the pages would otherwise validate):

[ Non-Standard html codes (127 - 159) ] [ Extended ASCII Codes (128 - 255) ]

References

For a detailed discussion of this, see On the use of some MS Windows characters in HTML at IT and communication: Yucca's free information site.

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