94 lines
6.4 KiB
HTML
94 lines
6.4 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Unicode considerations for display files" />
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<meta name="abstract" content="Unicode is a universal encoding scheme for written characters and text that enables the exchange of data internationally. Two transformation formats, UTF_16 and UCS_2, of Unicode are supported with DDS." />
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<meta name="description" content="Unicode is a universal encoding scheme for written characters and text that enables the exchange of data internationally. Two transformation formats, UTF_16 and UCS_2, of Unicode are supported with DDS." />
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<meta name="DC.subject" content="Unicode, display files, DDS file considerations, DDS file considerations" />
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<meta name="keywords" content="Unicode, display files, DDS file considerations, DDS file considerations" />
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<meta name="DC.Relation" scheme="URI" content="kickoff.htm" />
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<meta name="DC.Relation" scheme="URI" content="ucs2pos.htm" />
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<meta name="DC.Relation" scheme="URI" content="ucs2kwd.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2001, 2006" />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Unicode considerations for display files</title>
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</head>
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<body id="dspfil"><a name="dspfil"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Unicode considerations for display files</h1>
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<div><p>Unicode is a universal encoding scheme for written characters and
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text that enables the exchange of data internationally. Two transformation
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formats, UTF_16 and UCS_2, of Unicode are supported with DDS.</p>
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<p> A Unicode field in a display file can contain UCS-2 or UTF-16 data. Unicode
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data is composed of <em>code units</em>, which represent the minimal byte combination
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that can represent a unit of text.</p>
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<p>There are two transformation formats (encoding forms) of Unicode that are
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supported with DDS:</p>
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<ul><li><strong>UTF-16</strong> is a 16-bit encoding form designed to provide code values
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for over a million characters and a superset of Unicode. UTF-16 data is stored
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in graphic data types. The CCSID value for data in UTF-16 format is 1200. <p>A
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UTF-16 code unit is 2 bytes in length. A UTF-16 character can be 1 or 2 code
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units (2 or 4 bytes) in length. A UTF-16 data string can contain any character
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including UTF-16 surrogates and combining characters.</p>
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</li>
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<li><strong>UCS-2</strong> is the Universal Character Set coded in 2 octets, which means
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that characters are represented in 16 bits per character. One code unit is
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used in this topic to describe the size of a UCS-2 character. UCS-2 data is
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stored in graphic data types. The CCSID value for data in UCS-2 format is
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13488. <p>UCS-2 is a subset of UTF-16 and can no longer support all of the
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characters defined by Unicode. UCS-2 is identical to UTF-16 except that UTF-16
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also supports the combining of characters and surrogates. If you do not need
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support for the combining of characters and surrogates, you can choose to
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continue to use the UCS-2 format.</p>
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</li>
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</ul>
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<p>Unicode data is not supported on display devices that currently support
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the 5250 data stream. Therefore, conversions between the Unicode data and
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EBCDIC are necessary during input and output. On output, the Unicode data
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is converted to the CCSID of the device. On input, the data is converted from
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the device CCSID to the Unicode CCSID.</p>
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<p>Because the device CCSID, which is determined from the device configuration,
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determines what the Unicode data is converted to, the converted data will
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appear differently on different devices. For example, a Unicode code unit
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that maps to a SBCS character will be displayed as a DBCS replacement character
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on a graphic-DBCS capable device. On a DBCS or SBCS capable device, the code
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unit will appear as a SBCS character. A Unicode code unit that maps to a DBCS
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character will be displayed as a graphic-DBCS character on a graphic-DBCS
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capable device. On a DBCS device, a DBCS character will be displayed and bracketed
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(enclosed in a shift-out and shift-in). A SBCS replacement character will
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be displayed on a SBCS device.</p>
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<p>It is also suggested that all fields that
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are capable of Unicode are initialized in the output buffer before writing
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the fields to the screen. Unpredictable results might occur if default initialization
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is allowed to take place.</p>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="ucs2pos.htm">Positional entry considerations for display files that use Unicode data</a></strong><br />
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The topic describes, by position, DDS for describing display files. Positions not mentioned have no special considerations for Unicode.</li>
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<li class="ulchildlink"><strong><a href="ucs2kwd.htm">Keyword considerations for display files that use Unicode data (positions 45 through 80)</a></strong><br />
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The DFT keyword can contain SBCS, bracketed-DBCS, or bracketed-DBCS-graphic character strings when specified on a Unicode-capable field.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="kickoff.htm" title="Use data description specifications (DDS) to define display files. This topic collection provides the information you need to code the positional and keyword entries that define these files.">DDS for display files</a></div>
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</div>
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</div>
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</body>
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</html>
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