File: //proc/self/root/proc/self/root/usr/share/doc/freetds-0.95.81/userguide/aboutunicode.htm
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<HTML
><HEAD
><TITLE
>About Unicode, UCS-2, and UTF-8</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REL="HOME"
TITLE="FreeTDS User Guide"
HREF="index.htm"><LINK
REL="PREVIOUS"
TITLE="What it looks like"
HREF="interfacesformat.htm"><LINK
REL="NEXT"
TITLE="ISO 8859: What everyone would like to forget"
HREF="iso8859.htm"><LINK
REL="STYLESHEET"
TYPE="text/css"
HREF="userguide.css"><META
HTTP-EQUIV="Content-Type"
CONTENT="text/html; charset=utf-8"></HEAD
><BODY
CLASS="APPENDIX"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
><SPAN
CLASS="PRODUCTNAME"
>FreeTDS</SPAN
> User Guide: A Guide to Installing, Configuring, and Running <SPAN
CLASS="PRODUCTNAME"
>FreeTDS</SPAN
></TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="interfacesformat.htm"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="iso8859.htm"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="APPENDIX"
><H1
><A
NAME="ABOUTUNICODE"
></A
>Appendix C. About Unicode, UCS-2, and UTF-8</H1
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="aboutunicode.htm#ASCII"
><ACRONYM
CLASS="ACRONYM"
>ASCII</ACRONYM
>: What everyone knows</A
></DT
><DT
><A
HREF="iso8859.htm"
>ISO 8859: What everyone would like to forget</A
></DT
><DT
><A
HREF="unicode.htm"
>Unicode: East meets West</A
></DT
><DT
><A
HREF="unicodegoodbad.htm"
>Unicode's Pluses and Minuses</A
></DT
><DT
><A
HREF="unicodeutf.htm"
>Unicode Transformation Format: UTF-8</A
></DT
><DT
><A
HREF="unicodefreetds.htm"
>Unicode and <SPAN
CLASS="PRODUCTNAME"
>FreeTDS</SPAN
></A
></DT
></DL
></DIV
><P
>For better or worse, <SPAN
CLASS="PRODUCTNAME"
>FreeTDS</SPAN
> brings the otherwise innocent programmer into contact with the arcane business of how data are stored and transported. <SPAN
CLASS="PRODUCTNAME"
>FreeTDS</SPAN
> is a data communications library that of course connects to databases, which are charged with storing information in a way that is neutral to all architectures and languages. On the surface, that might not seem very complex, even worth discussing. Under the surface, things are not so simple.</P
><DIV
CLASS="SECTION"
><H1
CLASS="SECTION"
><A
NAME="ASCII"
><ACRONYM
CLASS="ACRONYM"
>ASCII</ACRONYM
>: What everyone knows</A
></H1
><P
>The world we are all familiar with, programmingwise, is <ACRONYM
CLASS="ACRONYM"
>ASCII</ACRONYM
>. Our email (mostly), our <SPAN
CLASS="QUOTE"
>"text"</SPAN
> files, our web pages (mostly), all use <ACRONYM
CLASS="ACRONYM"
>ASCII</ACRONYM
> to represent English (or English-like) text. Perhaps because <A
HREF="http://czyborra.com/charsets/iso646.html"
TARGET="_top"
><ACRONYM
CLASS="ACRONYM"
>ASCII</ACRONYM
></A
> was standardized back in 1972 by the ISO, it seems like the <SPAN
CLASS="QUOTE"
>"natural"</SPAN
> way to store information. But let's look under the hood a little bit, and examine our assumptions.</P
><P
>Our so-called <SPAN
CLASS="QUOTE"
>"text"</SPAN
> files are nothing special, nothing but a little agreement we enter into with our operating system. The only reason we can <SPAN
CLASS="QUOTE"
>"read"</SPAN
> them with <B
CLASS="COMMAND"
>cat</B
> or <B
CLASS="COMMAND"
>vi</B
> is that the operating system and its tools are in on the agreement. A file is only a stream of bytes, after all, no more <SPAN
CLASS="QUOTE"
>"text"</SPAN
> than an executable. The only thing distinguishing a <SPAN
CLASS="QUOTE"
>"text"</SPAN
> file from any other, is our understanding to treat it like one. We agree that the number 65 will represent the letter <TT
CLASS="LITERAL"
>A</TT
>, 66, <TT
CLASS="LITERAL"
>B</TT
>, and so on, 127 values in all. See <B
CLASS="COMMAND"
>man ascii</B
> for further details.</P
><P
>The important thing to understand is that the designation of 65 for <TT
CLASS="LITERAL"
>A</TT
> and so on is a choice. It's an <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>encoding standard</I
></SPAN
>, made necessary by the old simple fact that computers store numbers, not letters. <ACRONYM
CLASS="ACRONYM"
>ASCII</ACRONYM
> is so ubiquitous these days that it's hard sometimes to remember there was a time when it was but one of a set of competing encoding standards. Others you probably have heard of include <ACRONYM
CLASS="ACRONYM"
>EBCDIC</ACRONYM
> and the Baudot systems, but they are by no means the only historical alternatives, nor the only modern ones.</P
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="ASCIICOMPACT"
>The <ACRONYM
CLASS="ACRONYM"
>ASCII</ACRONYM
> Compact</A
></H2
><P
>UNIX® and unix-like systems bought into <ACRONYM
CLASS="ACRONYM"
>ASCII</ACRONYM
> big time. Program code, filenames, string constants (and variables), configuration files, everything but everything is encoded in <ACRONYM
CLASS="ACRONYM"
>ASCII</ACRONYM
>. Practically every utility, command, and library assumes the <SPAN
CLASS="QUOTE"
>"text"</SPAN
> data will be <ACRONYM
CLASS="ACRONYM"
>ASCII</ACRONYM
>. At the dawn of the 21<SUP
>st</SUP
> century, there is widespread recognition that <ACRONYM
CLASS="ACRONYM"
>ASCII</ACRONYM
> will no longer suffice, but the art of upgrading all the computers and computer programmers is, well, an unfinished work.</P
></DIV
></DIV
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="interfacesformat.htm"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.htm"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="iso8859.htm"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>What it looks like</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
> </TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>ISO 8859: What everyone would like to forget</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>