View source for Vietnamese language and computers

The [[Vietnamese language]] is written with a [[Latin-script alphabet|Latin script]] with diacritics ([[Diacritic|accent tones]]) which requires several accommodations when typing on phone or computers. Software-based systems are a form of writing Vietnamese on phones or computers with software that can be installed on the device or from third-party software such as [[UniKey (software)|UniKey]]. [[Telex (input method)|Telex]] is the oldest input method devised to encode the Vietnamese language with its tones. Other input methods may also include [[VNI]] (Number key-based keyboard) and [[VIQR]]. VNI input method is not to be confused with VNI code page.

Historically, Vietnamese was also written in ''{{lang|vi|[[chữ Nôm]]}}'', which is mainly used for ceremonial and traditional purposes in recent times, and remains in the field of historians and [[Philology|philologists]]. There have been attempts to type [[chữ Hán]] and [[chữ Nôm]] with existing Vietnamese input methods, but they are not widespread.<ref>{{Cite web |title=How to type Hán Nôm characters? |url=https://winvnkey.sourceforge.net/webhelp/winvnkey_manual/f_how_to_type_characters/how_to_type_han_nom_characters_.htm |access-date=2022-12-08 |website=winvnkey.sourceforge.net}}</ref><ref>{{Cite web |title=Chu Nom Resources |url=https://chunom.org/pages/links/ |access-date=2022-12-08 |website=chunom.org}}</ref> Sometimes, Vietnamese can be typed without tone marks, which Vietnamese speakers can usually guess depending on context.

==Fonts and character encodings==

===Vietnamese alphabet===
{{Multiple image |width=220
| direction = vertical
| image1 = Hook (diacritic).svg
| image2 = Hook (diacritic) in Calibri.png
| footer = It is common for two diacritics to be placed on a single Vietnamese vowel. Some fonts stack these diacritics, while others offset the tone mark.
}}

====Character encodings====
There are as many as 46 [[character encoding]]s for representing the [[Vietnamese alphabet]].<ref name="WinVNKey manual">{{cite web|title=Express Manual for WinVNKey|author1=Ngô Đình Học|author2=Trần Tư Bình|work=WinVNKey|date=July 21, 2014|access-date=October 5, 2014|url=http://winvnkey.sourceforge.net/express-manual-for-winvnkey.htm#The_charsets_in_WinVNKey}}</ref> [[Unicode]] has become the most popular form for many of the world's writing systems, due to its great compatibility and software support. Diacritics may be encoded either as [[combining character]]s or as [[precomposed character]]s, which are scattered throughout the [[Latin-1 Supplement]], [[Latin Extended-A]], [[Latin Extended-B]], and [[Latin Extended Additional]] blocks. The [[Vietnamese đồng]] symbol is encoded in the [[Currency Symbols (Unicode block)|Currency Symbols]] block.

Unicode's coverage of Vietnamese has been subject to several changes since the 1990s. Early versions of Unicode encoded {{lang|vi|dấu huyền}} and {{lang|vi|dấu sắc}} as {{unichar|0340|cwith=◌}} and {{unichar|0341|cwith=◌}}, respectively. In 2001, these two characters were deprecated as duplicate encodings of {{unichar|0300|cwith=◌}} and {{unichar|0301|cwith=◌}};<ref>{{cite report|title=Unicode Consortium Liaison Report|author=ISO/IEC JTC1/SC2/WG2|publisher=[[International Organization for Standardization]]|date=October 10, 2001|id=L2/01-378|accessdate=July 5, 2024|url=https://www.unicode.org/L2/L2001/01378-n2370-liaison-rpt-singapore.htm}}</ref> this change was incorporated into Unicode 3.2, released in 2002.<ref>{{cite report|title=Analysis of Character Deprecation in the Unicode Standard|first=Ken|last=Whistler|publisher=Unicode Technical Committee|date=August 1, 2001|id=L2/01-301|accessdate=July 5, 2024|url=https://www.unicode.org/L2/L2001/01301-deprecation.txt}}</ref> With the 2009 release of Unicode 5.2, {{unichar|0340|cwith=◌|name=none}} and {{unichar|0341|cwith=◌|name=none}} were undeprecated but discouraged.<ref>{{cite web|title=Combining Diacritical Marks|work=Unicode 7.0 Character Code Charts|publisher=[[Unicode Consortium]]|date=June 16, 2014|access-date=October 5, 2014|url=https://www.unicode.org/charts/nameslist/n_0300.html}}</ref><ref>{{cite report|title=Deprecation Inconsistencies in Code Chart Annotations|first=Charlotte|last=Buff|publisher=Unicode Technical Committee|date=September 16, 2018|id=L2/18-301|accessdate=July 5, 2024|url=https://www.unicode.org/L2/L2018/18301-deprecation.pdf}}</ref> Historically, the Vietnamese language used other characters beyond the modern alphabet. The [[Vietnamese language#Middle Vietnamese|Middle Vietnamese]] letter [[B with flourish]] (ꞗ) is included in the [[Latin Extended-D]] block. The [[Vietnamese tilde|apex]] is not separately encoded in Unicode, because it derives from the Portuguese [[tilde]], whereas {{lang|vi|dấu ngã}}, which derives from the Greek ''[[perispomeni]]'', has always been misencoded as a tilde. As a workaround, {{unichar|1dc3|cwith=◌}} represents the apex on [[Wikisource]] and [[Wiktionary]].

For systems that lack support for Unicode, dozens of 8-bit Vietnamese [[code page]]s have been designed.<ref name="WinVNKey manual"/> The most commonly used of them were [[VISCII]], [[VSCII]] (TCVN 5712:1993), [[VNI Character Set|VNI]], [[VPS character encoding|VPS]] and [[Windows-1258]].<ref name="wvnk">{{cite web |url=http://winvnkey.sourceforge.net/some-special-functions-of-winvnkey.htm#Why_having_Vietnamese_charset_conversion |title=5. Why Having Vietnamese Charset (Character Set – Encoding) Conversion? |work=Some special functions of WinVNKey |first1=Hoc Dinh |last1=Ngo |first2=TuBinh |last2=Tran}}</ref><ref name="BGTV fonts">{{cite web|title=Chọn Font chữ, bảng mã để gõ tiếng Việt|work=Bộ gõ tiếng Việt.Com|publisher=MangVN|year=2009|url=http://bogotiengviet.com/fontchu-bangma.htm|language=vi|archive-url=https://web.archive.org/web/20101120102739/http://bogotiengviet.com/fontchu-bangma.htm|archive-date=November 20, 2010}}</ref> Where [[ASCII]] is required, such as when ensuring readability in plain text e-mail, Vietnamese letters are often encoded according to [[Vietnamese Quoted-Readable]] (VIQR) or [[VSCII]] Mnemonic (VSCII-MNEM),<ref name="Lunde">{{cite book|title=CJKV Information Processing|edition=2nd|first=Ken|last=Lunde|author-link=Ken Lunde|publisher=[[O'Reilly Media]]|year=2009|pages=47–49|isbn=978-0-596-51447-1|via=Google Books|url=https://books.google.com/books?id=SA92uQqTB-AC&pg=PA47}}</ref> though usage of either variable-width scheme has declined dramatically following the adoption of Unicode on the [[World Wide Web]]. For instance, support for all above mentioned 8-bit encodings, with the exception of Windows-1258, was dropped from [[Mozilla]] software in 2014.<ref>{{cite web |url=https://groups.google.com/d/msg/mozilla.dev.apps.thunderbird/2P5kCJJS_WI/oWhT0STivL0J |last=Sivonen |first=Henri |title=Character encoding changes in m-c require c-c action |work=mozilla.dev.apps.thunderbird |date=2014-09-26}}</ref>

Many Vietnamese fonts intended for [[desktop publishing]] are encoded in [[VNI#VNI Encoding|VNI]] or TCVN3 ([[VSCII]]).<ref name="BGTV fonts"/> Such fonts are known as "ABC fonts".<ref name="Hoang To">{{cite book|title=Sử ký Tinh Vân: 20 năm sẻ chia và sáng tạo|trans-title=History of Tinhvan: 20 years of sharing and creating|volume=1|author1=Hoàng Tô|author2=Nguyễn Quan Sơn|author3=Nguyễn Sơn Tùng|author4=Phan Quang Minh|author5=Phạm Thúc Trương Lương|author6=Nguyễn Quang Hiệp|author7=Bùi Văn Kiên|author8=Nguyễn Ích Vinh|publisher=Tinhvan Group|date=20 July 2014|page=37|via=Google Books|url=https://books.google.com/books?id=aaZABAAAQBAJ&pg=PA37|language=vi}}</ref> Popular [[web browser]]s lack support for specialty Vietnamese encodings, so any webpage that uses these fonts appears as unintelligible ''[[mojibake]]'' on systems without them installed.

[[File:I acute - soft dotted and Lithuanian dot.svg|thumb|right|At right, an ''í'' that retains its [[tittle]]]]

Vietnamese often stacks diacritics, so typeface designers must take care to prevent stacked diacritics from colliding with adjacent letters or lines. When a tone mark is used together with another diacritic, offsetting the tone mark to the right preserves consistency and avoids slowing down [[saccade]]s.<ref>{{cite web|title=Design Challenges|first=Donny|last=Trương|work=Vietnamese Typography|access-date=April 10, 2018|url=https://vietnamesetypography.com/design-challenges/}}</ref> In advertising signage and in [[cursive]] handwriting, diacritics often take forms unfamiliar to other Latin alphabets. For example, the lowercase letter I retains its [[tittle]] in ''ì'', ''ỉ'', ''ĩ'', and ''í''.<ref>See, for example: {{cite book|chapter=Viết Thư|title=Vietnamese reading selections|edition=2|publisher=[[w:Defense Language Institute|Army Language School]]|year=1956|pages=98–100|url=http://babel.hathitrust.org/cgi/pt?id=mdp.39015082440291;view=1up;seq=4|language=vi}}</ref> These nuances are rarely accounted for in computing environments.

====Approaches to character encoding====
Vietnamese writing requires 134 additional letters (between both cases) besides the 52 already present in ASCII.<ref name="rep92" /> This exceeds the 128 additional characters available in a conventional [[extended ASCII]] encoding. Although this can be solved by using a [[variable-width encoding]] (as is done by [[UTF-8]]), a number of approaches have been used by other encodings to support Vietnamese without doing so:

* Replace at least six ASCII characters, selected either for being uncommon in Vietnamese, and/or for being non-invariant in [[ISO 646]] or [[DEC NRCS]]<ref name="rep92">{{cite tech report |url=http://vietstd.sourceforge.net/report/rep92.htm |title=Vietnamese Character Encoding Standardization Report - VISCII And VIQR 1.1 Character Encoding Specifications |date=1992 |publisher=Viet-Std Group |page=10 |section=2. Review Of Current Conventions}}</ref> (as in [[VNI#VNI Encoding for DOS|VNI for DOS]]).
* Drop the uppercase letters which are least frequently used,<ref name="rep92" /> or all uppercase letters with tone marks (as in [[VSCII|VSCII-3]] (TCVN3)). These letters may still be supplied by means of all-capital fonts.<ref>{{cite web |url=http://vietunicode.sourceforge.net/charset/ |title=Unicode & Vietnamese Legacy Character Encodings |work=Vietnamese Unicode FAQs |quotation=TCVN3 is not double-byte, but due to the nature of its encoding, capital letters (vowels) are mapped to a separate, capital font that is similar to the normal, lowercase one.}}</ref>
* Drop forms of the letter Y with tone marks, necessitating [[Vietnamese alphabet#Pronunciation|use of the letter {{serif|I}} in those circumstances]]. This approach was rejected by the designers of [[VISCII]] on the basis that a character encoding should not attempt to settle a spelling reform issue.<ref name="rep92" />
* Replace at least six [[C0 control characters]]<ref name="rep92" /> (as in [[VISCII]], [[VSCII|VSCII-1]] (TCVN1) and [[VPS character encoding|VPS]]).
* Use combining characters, allowing one vowel with accents to be fully represented using a sequence of characters (as in [[VNI Character Set|VNI]], [[VSCII|VSCII-2]] (TCVN2), [[Windows-1258]] and [[ANSEL]]).

====Unicode code points====
The following table provides Unicode code points for all non-ASCII Vietnamese letters.

{| class="wikitable" style="text-align: center"
! Unmarked !! Grave !! Hook !! Perispomeni !! Acute !! Dot
|-
| || ̀ (U+0300) || ̉ (U+0309) || ̃ (U+0303) || ́ (U+0301) || ̣ (U+0323)
|-
! colspan="6" | Uppercase letters
|-
| A || À (U+00C0) || Ả (U+1EA2) || Ã (U+00C3) || Á (U+00C1) || Ạ (U+1EA0)
|-
| Ă (U+0102) || Ằ (U+1EB0) || Ẳ (U+1EB2) || Ẵ (U+1EB4) || Ắ (U+1EAE) || Ặ (U+1EB6)
|-
| Â (U+00C2) || Ầ (U+1EA6) || Ẩ (U+1EA8) || Ẫ (U+1EAA) || Ấ (U+1EA4) || Ậ (U+1EAC)
|-
| Đ (U+0110) || colspan="5" |
|-
| E || È (U+00C8) || Ẻ (U+1EBA) || Ẽ (U+1EBC) || É (U+00C9) || Ẹ (U+1EB8)
|-
| Ê (U+00CA) || Ề (U+1EC0) || Ể (U+1EC2) || Ễ (U+1EC4) || Ế (U+1EBE) || Ệ (U+1EC6)
|-
| I || Ì (U+00CC) || Ỉ (U+1EC8) || Ĩ (U+0128) || Í (U+00CD) || Ị (U+1ECA)
|-
| O || Ò (U+00D2) || Ỏ (U+1ECE) || Õ (U+00D5) || Ó (U+00D3) || Ọ (U+1ECC)
|-
| Ô (U+00D4) || Ồ (U+1ED2) || Ổ (U+1ED4) || Ỗ (U+1ED6) || Ố (U+1ED0) || Ộ (U+1ED8)
|-
| Ơ (U+01A0) || Ờ (U+1EDC) || Ở (U+1EDE) || Ỡ (U+1EE0) || Ớ (U+1EDA) || Ợ (U+1EE2)
|-
| U || Ù (U+00D9) || Ủ (U+1EE6) || Ũ (U+0168) || Ú (U+00DA) || Ụ (U+1EE4)
|-
| Ư (U+01AF) || Ừ (U+1EEA) || Ử (U+1EEC) || Ữ (U+1EEE) || Ứ (U+1EE8) || Ự (U+1EF0)
|-
| Y || Ỳ (U+1EF2) || Ỷ (U+1EF6) || Ỹ (U+1EF8) || Ý (U+00DD) || Ỵ (U+1EF4)
|-
! colspan="6" | Lowercase letters
|-
| a || à (U+00E0) || ả (U+1EA3) || ã (U+00E3) || á (U+00E1) || ạ (U+1EA1)
|-
| ă (U+0103) || ằ (U+1EB1) || ẳ (U+1EB3) || ẵ (U+1EB5) || ắ (U+1EAF) || ặ (U+1EB7)
|-
| â (U+00E2) || ầ (U+1EA7) || ẩ (U+1EA9) || ẫ (U+1EAB) || ấ (U+1EA5) || ậ (U+1EAD)
|-
| đ (U+0111) || colspan="5" |
|-
| e || è (U+00E8) || ẻ (U+1EBB) || ẽ (U+1EBD) || é (U+00E9) || ẹ (U+1EB9)
|-
| ê (U+00EA) || ề (U+1EC1) || ể (U+1EC3) || ễ (U+1EC5) || ế (U+1EBF) || ệ (U+1EC7)
|-
| i || ì (U+00EC) || ỉ (U+1EC9) || ĩ (U+0129) || í (U+00ED) || ị (U+1ECB)
|-
| o || ò (U+00F2) || ỏ (U+1ECF) || õ (U+00F5) || ó (U+00F3) || ọ (U+1ECD)
|-
| ô (U+00F4) || ồ (U+1ED3) || ổ (U+1ED5) || ỗ (U+1ED7) || ố (U+1ED1) || ộ (U+1ED9)
|-
| ơ (U+01A1) || ờ (U+1EDD) || ở (U+1EDF) || ỡ (U+1EE1) || ớ (U+1EDB) || ợ (U+1EE3)
|-
| u || ù (U+00F9) || ủ (U+1EE7) || ũ (U+0169) || ú (U+00FA) || ụ (U+1EE5)
|-
| ư (U+01B0) || ừ (U+1EEB) || ử (U+1EED) || ữ (U+1EEF) || ứ (U+1EE9) || ự (U+1EF1)
|-
| y || ỳ (U+1EF3) || ỷ (U+1EF7) || ỹ (U+1EF9) || ý (U+00FD) || ỵ (U+1EF5)
|}

====Font substitution====
Many fonts support a subset of the Latin writing system that omits much of the Vietnamese alphabet. Due to the high density of Vietnamese-specific characters in Vietnamese text, Web browsers that implement [[font substitution]] reliably produce a [[ransom note effect]] when the webpage specifies an inadequate font.

===''{{lang|vi|Chữ Nôm}}''===
[[File:Phở.png|alt=𬖾|thumb|The ''{{lang|vi|nôm}}'' character for ''{{lang|vi|[[pho|phở]]}}''<ref name="Kiem">{{cite encyclopedia |year=2004 |title=phở |url=http://nomfoundation.org/nom-tools/Nom-Dictionary |edition=4th |language=vi |author=Trần Văn Kiệm |encyclopedia=Giúp đọc Nôm và Hán Việt}} [http://nomfoundation.org/common/nom_details.php?codepoint=6309d&img=1]</ref>]]
Unicode includes over 10,000 ''{{lang|vi|Nôm}}'' characters as part of Unicode's repertoire of [[CJK Unified Ideographs]]. Of these characters, 10,082 can be found in the [[CJK Unified Ideographs Extension B]] block, while the rest are distributed between the [[CJK Unified Ideographs]], [[CJK Unified Ideographs Extension A]], and [[CJK Unified Ideographs Extension C]] blocks. A further 1,028 characters, including over 400 characters specific to the [[Tày language]], are encoded in the [[CJK Unified Ideographs Extension E]] block. The characters are taken from the Vietnamese standards [[TCVN 5773:1993]] and [[TCVN 6909:2001]] [error for TCVN 6056:1995?], as well as from research by the Han-Nom Research Institute and other groups.<ref name="VNPF Hồng">{{cite web|author=Nguyễn Quang Hồng|title=Giới thiệu Kho chữ Hán Nôm mã hoá|trans-title=Hán Nôm Coded Character Repertoire Introduction|publisher=Vietnamese Nôm Preservation Foundation|url=http://nomfoundation.org/vn/du-an-nom/Kho-chu-Han-Nom-ma-hoa/Gioi-thieu-Kho-chu-Han-Nom-ma-hoa|language=vi}}</ref> All the characters in TCVN 5773:1993 and about 95% of the characters in TCVN 6909:2001 [error for TCVN 6056:1995?] have corresponding codepoints in Unicode 5.1, though TCVN 5773:1993 itself mapped most of its characters to the [[Private Use Area]] of Unicode.{{sfn|Lunde|2009|pp=152–153}} Unicode 13.0 added two diacritical characters to the [[Ideographic Symbols and Punctuation]] block that were commonly used to indicate borrowed characters in {{lang|vi|chữ Nôm}}.<ref>{{cite web|title=Proposal to Encode Two Vietnamese Alternate Reading Marks|first1=Lee|last1=Collins|author2=Ngô Thanh Nhàn|date=6 November 2017|url=https://www.unicode.org/L2/L2017/17373r-viet-alt-reading-marks.pdf}}</ref><ref>{{cite web|title=Proposed New Characters: The Pipeline |publisher=Unicode Consortium|date=8 May 2019|access-date=26 May 2019|url=https://www.unicode.org/alloc/Pipeline.html}}</ref>

The two most comprehensive ''{{lang|vi|Nôm}}'' fonts are the [[Vietnamese Nôm Preservation Foundation]]'s ''{{lang|vi|Nôm Na Tống}} Light''<ref>{{cite web|title=Nôm Font|publisher=Vietnamese Nôm Preservation Foundation|access-date=October 5, 2014|url=http://nomfoundation.org/nom-tools/Nom-Font}}</ref> and the community-developed ''HAN NOM A''/''HAN NOM B'',<ref>{{cite web|title=UNICODE Han Nom Font Set|author1=Đỗ Quốc Bảo|author2=Tô Minh Tâm|author3=Thiền Viện Viên Chiếu|date=December 8, 2005|access-date=October 5, 2014|url=http://vietunicode.sourceforge.net/fonts/fonts_hannom.html}}</ref> both of which place a large number of unstandardized characters in the [[Private Use Areas]].

The Unicode Consortium's [[Han unification#Unihan database files|Unihan]] database includes Vietnamese readings of some characters but does not distinguish between [[Sino-Vietnamese vocabulary|Sino-Vietnamese]] and ''{{lang|vi|Nôm}}'' readings.

Like other [[CJK characters|CJKV writing systems]], ''{{lang|vi|chữ Nôm}}'' is traditionally [[Horizontal and vertical writing in East Asian scripts|written vertically]], from top to bottom and right to left.

{{lang|vi|Chữ Hán}} and {{lang|vi|chữ Nôm}} may also be annotated using [[ruby character]]s, which is the same as [[Chữ Quốc ngữ|chữ Quốc Ngữ]] for Vietnamese.{{sfn|Lunde|2009|p=529}}

==Text input==
[[File:Typewriter-aderty-vn.jpg|thumb|Typewriter Olympia Splendid 33, AĐERTY layout (based on [[AZERTY]]), used in Vietnam in the 1960s, seen at Museum of Ho Chi Minh City]]
A purely physical Vietnamese keyboard would be impractical, due to the sheer number of letter-diacritic-diacritic combinations in the alphabet e.g. ờ, ị.  Instead, Vietnamese input relies on formulaic software-based keyboard layouts, [[virtual keyboard]]s, or [[input method]]s (also known as IMEs).

===Keyboard layouts===
{{Multiple image |width=300
| direction = vertical
| image1 = Vietnamese keyboard.svg | caption1 = [[Microsoft Windows]] includes a Vietnamese keyboard layout based on TCVN 6064:1995.
| image2 = Vietnamese typewriter keyboard.svg | caption2 = AZERTY-based Vietnamese typewriter keyboard layout
}}
Vietnamese keyboard layouts rely on [[dead key]]s to compose letters with diacritics. Most desktop operating systems include a Vietnamese keyboard layout similar to {{interlanguage link|TCVN 6064:1995|vi}}, a Vietnamese national standard. Previously, typewriters used an AZERTY-based Vietnamese layout (AĐERTY).<ref>{{Citation|last=Duncan|first=John William|title=VietNamese Typewriter|date=2005-12-22|url=https://www.flickr.com/photos/13712099@N05/1503345730/|access-date=2020-07-11}}</ref>

===Input methods===
[[File:Xvnkb-screenshot.png|thumb|left|upright|xvnkb, an IME compatible with the [[X Input Method]] framework on Unix systems, supports output in six character encodings.]]

The three most common Vietnamese input methods are [[Telex (input method)|Telex]], [[VNI#VNI Input Method|VNI]], and [[Vietnamese Quoted-Readable|VIQR]]. Telex indicates diacritics using letters that are unlikely to appear at the end of a word, while VNI repurposes the number keys or function keys and VIQR repurposes various punctuation marks. The Telex and VIQR conventions originated in an earlier era of [[telex]] machines and typewriters, respectively.

Support for these input methods is provided by input method editors (IMEs), which are known in Vietnamese as ''{{lang|vi|bộ gõ}}'', literally "peckers", "typing sets" or "percussion" in more general terms. IMEs may be provided by the operating system, installed as a third-party application, installed as a [[browser extension]], or provided by an individual website in the form of a [[Scripting language|script]]. Common third-party applications include GoTiengViet, [[UniKey (IME)|UniKey]], VietKey, [[VPSKeys]], [[WinVNKey]], and xvnkb. On [[Unix-like]] operating systems, the [[Intelligent Input Bus|IBus]] and [[Smart Common Input Method|SCIM]] frameworks both support Vietnamese. IME scripts such as AVIM, Mudim, and VietTyping can be found on most Vietnamese [[Internet forum|message board]]s, the [[Vietnamese Wikipedia]], and other text-intensive websites. The Vietnamese Web browser [[Cốc Cốc]] comes with an input method built-in.

Input methods allow words to be composed in a more flexible order than keyboard layouts allow. For example, to enter the word "{{lang|vi|[[wikt:viết|viết]]}}" using the TCVN 6064:1995 keyboard layout, one must type {{key press|V}}{{key press|I}}{{key press|3}}{{key press|8}}{{key press|T}}, in that order. By contrast, most IMEs permit the user to insert diacritics at the end of the word: {{key press|V}}{{key press|I}}{{key press|E}}{{key press|E}}{{key press|T}}{{key press|S}} in Telex, {{key press|V}}{{key press|I}}{{key press|E}}{{key press|T}}{{key press|6}}{{key press|1}} in VNI, or {{key press|V}}{{key press|I}}{{key press|E}}{{key press|T}}{{key press|^}}{{key press|'}} in VIQR. Some IMEs even allow diacritics to be entered before their base letters. Depending on an IME's implementation, it may also be possible to edit an existing word's diacritics without retyping the word.

Some [[virtual keyboard]]s supplement the standard dead keys with dedicated shortcut keys. For example, with the VIQR keyboard built into [[iOS]], it is possible to add a [[Horn (diacritic)|horn]] to "U" by tapping either {{key press|123}}{{key press|1=#+=}}{{key press|+}} or the dedicated {{key press|◌̛}} key, which has no analogue on a physical keyboard.

[[File:Lee's Supermarket help wanted sign.jpg|thumb|right|upright|When Vietnamese input methods are unavailable, Vietnamese text is commonly printed without diacritical marks and then handwritten on.]]

Borrowing a feature common amongst [[Chinese input methods for computers|Chinese input methods]], some Vietnamese IMEs allow one to skip diacritics altogether and instead, after typing the base letters, the user can select the accented word from a candidate list. In order to provide this [[autocomplete]] list, the IME may need to communicate with a [[Web service]]. Some IMEs also use candidate lists to allow the user to convert text from the Vietnamese alphabet to ''{{lang|vi|chữ Nôm}}'', because there is no one-to-one correspondence between alphabetic words and ''{{lang|vi|nôm}}'' characters.

==Other considerations==
Typical Vietnamese text contains a high proportion of compound words. Compound words are never hyphenated in contemporary usage, so [[spell checker]]s are limited to checking individual syllables unless a statistical [[language model]] is consulted.

Vietnamese has rigid spelling rules and few exceptions, so [[Speech synthesis|text-to-speech engine]]s may avoid dictionary lookups except when encountering a foreign loan word. TTS engines must account for [[tone (linguistics)|tone]]s, which are essential to the meaning of any Vietnamese word e.g. má (mother) is a different word to mà (but).

[[Internationalization and localization|Internationalized]] user interfaces are generally unable to use the full complement of [[Vietnamese pronouns]] that would be expected in a traditional social setting, even when much is known about the user. Instead, user interfaces typically use generic pronouns such as {{lang|vi|tôi}} and {{lang|vi|bạn}}, some of which make potentially incorrect assumptions about the user's age and relationship to other users. For example, when a [[social media]] platform notifies a user about a younger user, it may refer to the latter in the third person as {{lang|vi|anh ấy}} instead of {{lang|vi|em ấy}}, leading the user to misinterpret the notification as a reference to someone else.<ref>{{cite web|title=Language Guidelines – Vietnamese|first=Raquel|last=Jacob|publisher=[[Unbabel]]|date=February 2, 2022|accessdate=July 18, 2022|url=https://help.unbabel.com/hc/en-us/articles/360022945614-Language-Guidelines-Vietnamese#24pronouns}}</ref>

==See also==
* [[Chinese input methods for computers]]
* [[Japanese language and computers]]
* [[Korean language and computers]]

==References==
{{Reflist}}

==Further reading==
* {{cite book|ref=none|title=CJKV Information Processing|first=Ken|last=Lunde|author-link=Ken Lunde|location=Sebastopol, California|publisher=[[O'Reilly Media]]|year=2009|isbn=978-0-596-51447-1|url=https://books.google.com/books?id=SA92uQqTB-AC&pg=PA529|via=Google Books}}

==External links==
* [http://imug.org/presentations/VietComputing.pdf Computing in Vietnamese: Progress & Challenges]{{snd}} 2005 International Macintosh Users Group presentation
* [http://www.enderminh.com/minh/vnconversions.aspx Vietnamese Conversions]{{snd}} online tool for recovering Vietnamese [[mojibake]]

{{Vietnam topics}}
[[Category:Natural language and computing]]
[[Category:Science and technology in Vietnam]]
[[Category:Vietnamese character input]]
[[Category:Vietnamese software]]