Unicode in Microsoft Windows: Difference between revisions

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{{Short description|Overview on Unicode implementation in Microsoft Windows}}

{{more citations needed|date=June 2011}}

[[Microsoft]] was one of the first companies to implement [[Unicode]] in their products. [[Windows NT]] was the first operating system that used "wide characters" in [[system call]]s. Using the (now obsolete) [[UCS-2]] encoding scheme at first, it was upgraded to the [[variable-width encoding]] [[UTF-16]] starting with [[Windows 2000]], allowing a representation of additional planes with surrogate pairs. However Microsoft did not support [[UTF-8]] in its API until May 2019.

Before 2019, Microsoft emphasized UTF-16 (i.e. -W API), but has since recommended to use [[UTF-8]] for programs (at least in some cases),<ref name="Microsoft-UTF-8" /> on Windows and [[Xbox]] (and in other of its products), even states "UTF-8 is the universal code page for internationalization [and] UTF-16 [... is] a unique burden that Windows places on code that targets multiple platforms. [..] Windows [is] moving forward to support UTF-8 to remove this unique burden [resulting in] in fewer internationalization issues in apps and games".<ref>{{Cite web |titlename=UTF-8 support in the "Microsoft Game Development Kit (GDK)" - Microsoft Game Development Kit |url=https://learn.microsoft.com/en-us/gaming/gdk/_content/gc/system/overviews/utf-8 |access-date=2023-03-05 |website=learn.microsoft.com |language=en-us |quote=By operating in UTF-8, you can ensure maximum compatibility [..] Windows operates natively in UTF-16 (or WCHAR), which requires code page conversions by using MultiByteToWideChar and WideCharToMultiByte. This is a unique burden that Windows places on code that targets multiple platforms. [..] The Microsoft Game Development Kit (GDK) and Windows in general are moving forward to support UTF-8 to remove this unique burden of Windows on code targeting or interchanging with multiple platforms and the web. Also, this results in fewer internationalization issues in apps and games and reduces the test matrix that's required to get it right.}}</ref>

A large amount of Microsoft documentation uses the word "Unicode" to refer explicitly to the UTF-16 encoding. Anything else, including UTF-8, is not "Unicode" in Microsoft's outdated language (while UTF-8 and UTF-16 are both Unicode according to the [[Unicode|the Unicode standardStandard]], or encodings/"transformation formats" ofthereof).

== In various Windows families ==

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=== Windows CE ===

In (the now discontinued) [[Windows CE]], UTF-16 was used almost exclusively, with the 'A' API mostly missing.<ref>{{cite web|title=Differences Between the Windows CE and Windows NT Implementations of TAPI|url=https://msdn.microsoft.com/en-us/library/aa454022.aspx|website=MSDN|date=28 August 2006 |access-date=7 May 2018|quote=Windows CE is Unicode-based. You might have to recompile source code that was written for a Windows NT-based application.}}</ref> A limited set of ANSI API is available in Windows CE 5.0, for use on a reduced set of locales that may be selectively built onto the runtime image.<ref>{{cite web|title=Code Pages (Windows CE 5.0)|url=https://docs.microsoft.com/en-us/previous-versions/windows/embedded/ms903783(v=msdn.10)|website=Microsoft Docs| date=14 September 2012 |access-date=7 May 2018|language=en-us}}</ref>

{{expand section|date=June 2011}}

=== Windows 9x ===

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== UTF-8 ==

Microsoft Windows ([[Windows XP]] and later) has a code page designated for [[UTF-8]], code page 65001<ref>{{cite web|title=Code Page Identifiers (Windows)|url=https://msdn.microsoft.com/en-us/library/windows/desktop/dd317756(v=vs.85).aspx|website=msdn.microsoft.com| date=7 January 2021 |language=en}}</ref> or <code>CP_UTF8</code>. For a long time, it was impossible to set the locale code page to 65001, leaving this code page only available for (a) explicit conversion functions such as MultiByteToWideChar and/or (b) the [[Win32 console]] command <code>chcp 65001</code> to translate stdin/out between UTF-8 and UTF-16. This meant that "narrow" functions, in particular <code>[[C file input/output#fopen|fopen]]</code> (which opens files), couldn't be called with UTF-8 strings, and in fact there was no way to open all possible files using <code>fopen</code> no matter what the locale was set to and/or what bytes were put in the string, as none of the available locales could produce all possible UTF-16 characters. This problem also applied to all other APIs that take or return 8-bit strings, including Windows ones such as <code>SetWindowText</code>.

Programs that wanted to use UTF-8, in particular code intended to be portable to other operating systems, needed a workaround for this deficiency. The usual work-around was to add new functions to open files that convert UTF-8 to UTF-16 using [[MultiByteToWideChar]] and call the "wide" function instead of <code>fopen</code>.<ref>{{cite web|url=https://stackoverflow.com/questions/166503/utf-8-in-windows|title=UTF-8 in Windows|publisher=[[Stack Overflow]]|access-date=July 1, 2011}}</ref> Dozens of multi-platform libraries added wrapper functions to do this conversion on Windows (and pass UTF-8 through unchanged on others), an example is a proposed addition to [[Boost (C++ libraries)|Boost]], {{tt|Boost.Nowide}}.<ref>{{cite web|url=https://github.com/boostorg/nowide|title=Boost.Nowide|website=[[GitHub]]}}</ref> Another popular work-around was to convert the name to the [[8.3 filename]] equivalent, this is necessary if the <code>fopen</code> is inside a library. None of these workarounds are considered good, as they require changes to the code that works on non-Windows.

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In May 2019, Microsoft added the ability for a program to set the code page to UTF-8 itself,<ref name="Microsoft-UTF-8">{{cite web|title=Use UTF-8 code pages in Windows apps|url=https://learn.microsoft.com/en-us/windows/apps/design/globalizing/use-utf8-code-page |access-date=2020-06-06 |quote=As of Windows version&nbsp;1903 (May&nbsp;2019 update), you can use the ActiveCodePage property in the appxmanifest for packaged apps, or the fusion manifest for unpackaged apps, to force a process to use UTF-8 as the process code page. [...] <code>CP_ACP</code> equates to <code>CP_UTF8</code> only if running on Windows version&nbsp;1903 (May&nbsp;2019 update) or above and the ActiveCodePage property described above is set to UTF-8. Otherwise, it honors the legacy system code page. We recommend using <code>CP_UTF8</code> explicitly. |website=learn.microsoft.com |language=en-us}}</ref><ref>{{cite web|url=https://skanthak.homepage.t-online.de/quirks.html#quirk31|title=Windows 10 1903 and later versions finally support UTF-8 with the A forms of the Win32 functions}}</ref> allowing programs written to use UTF-8 to be run by non-expert users.

{{As of|2019}}, Microsoft recommends programmers use UTF-8 (e.g. instead of any other 8-bit encoding),<ref name="Microsoft-UTF-8">{{cite web|title=Use UTF-8 code pages in Windows apps|url=https://learn.microsoft.com/en-us/windows/apps/design/globalizing/use-utf8-code-page |access-date=2020-06-06 |quote=As of Windows version&nbsp;1903 (May&nbsp;2019 update), you can use the ActiveCodePage property in the appxmanifest for packaged apps, or the fusion manifest for unpackaged apps, to force a process to use UTF-8 as the process code page. [...] <code>CP_ACP</code> equates to <code>CP_UTF8</code> only if running on Windows version&nbsp;1903 (May&nbsp;2019 update) or above and the ActiveCodePage property described above is set to UTF-8. Otherwise, it honors the legacy system code page. We recommend using <code>CP_UTF8</code> explicitly. |website=learn.microsoft.com |language=en-us}}</ref> on Windows and [[Xbox]], and may be recommending it'sits use instead of UTF-16, even stating "UTF-8 is the universal code page for internationalization [and] UTF-16 [..] is a unique burden that Windows places on code that targets multiple platforms."<ref name="Microsoft GDK">{{Cite web |title=UTF-8 support in the Microsoft Game Development Kit (GDK) - Microsoft Game Development Kit |url=https://learn.microsoft.com/en-us/gaming/gdk/_content/gc/system/overviews/utf-8 |access-date=2023-03-05 |website=learn.microsoft.com |date=19 August 2022 |language=en-us |quote=By operating in UTF-8, you can ensure maximum compatibility [..] Windows operates natively in UTF-16 (or WCHAR), which requires code page conversions by using MultiByteToWideChar and WideCharToMultiByte. This is a unique burden that Windows places on code that targets multiple platforms. [..] The Microsoft Game Development Kit (GDK) and Windows in general are moving forward to support UTF-8 to remove this unique burden of Windows on code targeting or interchanging with multiple platforms and the web. Also, this results in fewer internationalization issues in apps and games and reduces the test matrix that's required to get it right.}}</ref> Microsoft does appear to be transitioning to UTF-8, stating it previously emphasized its alternative, and in [[Windows 11]] some system files are required to use UTF-8 and do not require a Byte Order Mark.<ref>{{Cite web|last=themar-msft|title=Customize the Windows 11 Start menu|url=https://docs.microsoft.com/en-us/windows-hardware/customize/desktop/customize-the-windows-11-start-menu|access-date=2021-06-29|website=docs.microsoft.com|language=en-us|quote=Make sure your LayoutModification.json uses UTF-8 encoding.}}</ref> Notepad can now recognize UTF-8 without the Byte Order Mark, and can be told to write UTF-8 without a Byte Order Mark.{{cn|date=November 2022}} Some other Microsoft products are using UTF-8 internally, including Visual Studio<ref>{{cncite web|title=New Options for Managing Character Sets in the Microsoft C/C++ Compiler|url=https://devblogs.microsoft.com/cppblog/new-options-for-managing-character-sets-in-the-microsoft-cc-compiler/#how-the-microsoft-c/c++-compiler-reads-text-from-a-file|website=devblogs.microsoft.com| date=November22 2022February 2016 |language=en |quote=At some point in the past, the Microsoft compiler was changed to use UTF-8 internally. So, as files are read from disk, they are converted into UTF-8 on the fly.}}</ref><ref>{{ cite web | title=validate-charset (validate for compatible characters) | website=docs.microsoft.com |language=en-us | url=https://docs.microsoft.com/en-us/cpp/build/reference/validate-charset-validate-for-compatible-characters | access-date=2021-07-19 | quote=Visual Studio uses UTF-8 as the internal character encoding during conversion between the source character set and the execution character set. }}</ref> and their [[SQL Server 2019]], with Microsoft claiming 35% speed increase from use of UTF-8, and "nearly 50% reduction in storage requirements."<ref>{{Cite web|date=2019-07-02|title=Introducing UTF-8 support for SQL Server|url=https://techcommunity.microsoft.com/t5/sql-server/introducing-utf-8-support-for-sql-server/ba-p/734928|quote=For example, changing an existing column data type from NCHAR(10) to CHAR(10) using an UTF-8 enabled collation, translates into nearly 50% reduction in storage requirements. [..] In the ASCII range, when doing intensive read/write I/O on UTF-8<!-- " " in quote, but ok to strip-->, we measured an average 35% performance improvement over UTF-16 using clustered tables with a non-clustered index on the string column, and an average 11% performance improvement over UTF-16 using a heap. |access-date=2021-08-24|website=techcommunity.microsoft.com|language=en}}</ref>

=== String constants in Visual Studio ===

=== Programming platforms ===

Before 2019 Microsoft's compilers oftencould failnot at producingproduce UTF-8 string constants from UTF-8 source files. TheThis mostis reliabledue to them converting all strings to the locale code page (which could not be UTF-8). At one time the only method isto work around this was to turn ''off'' {{tt|UNICODE}}, and ''not'' mark the input file as being UTF-8 (i.e. do not use a [[UTF-8#Byte order mark|BOM]]), and arrange the string constants to have the UTF-8 bytes. If a BOM was added, a Microsoft compiler will interpret the strings as UTF-8, convert them to UTF-16, then convert them ''back'' into the current locale, thus destroying the UTF-8.<ref>[http://utf8everywhere.org/#faq.literal UTF-8 Everywhere FAQ: How do I write UTF-8 string literal in my C++ code?]</ref> Without(note athat BOMthe and{{tt|u8"text"}} usingproposed asolution single-bytedoes localenot work, Microsoftstring compilersis willstill leavemangled)</ref> the bytesThis inwould amake quotedthe string unchanged. On moderncompiler systemsthink settingboth the codeinput pageand tooutputs UTF-8were helpsin considerably,the but invalidsame single-byte sequenceslocale, areand stillleave notstrings preserved (using {{code|\x}} can work around this)unmolested.

== See also ==