 | This article needs additional citations for verification .(January 2019) |
The left-to-right mark (LRM) is a control character (an invisible formatting character) used in computerized typesetting (including word processing in a program like Microsoft Word) of text containing a mix of left-to-right scripts (such as Latin and Cyrillic) and right-to-left scripts (such as Arabic, Syriac, and Hebrew). It is used to set the way adjacent characters are grouped with respect to text direction.
In Unicode, the LRM character is encoded at U+200ELEFT-TO-RIGHT MARK (‎). In UTF-8 it is E2 80 8E. Usage is prescribed in the Unicode Bidi (bidirectional) algorithm. [1]
Suppose the writer wishes to use some English text (a left-to-right script) into a paragraph written in Arabic or Hebrew (a right-to-left script) with non-alphabetic characters to the right of the English text. For example, the writer wants to translate, "The language C++ is a programming language used..." into Arabic. Without an LRM control character, the result looks like this:
لغة C++ هي لغة برمجة تستخدم...With an LRM entered in the HTML after the ++, it looks like this, as the writer intends:
لغة C++ هي لغة برمجة تستخدم...In the first example, without an LRM control character, a web browser will render the ++ on the left of the "C" because the browser recognizes that the paragraph is in a right-to-left text (Arabic) and applies punctuation, which is neutral as to its direction, according to the direction of the adjacent text. The LRM control character causes the punctuation to be adjacent to only left-to-right text – the "C" and the LRM – and position as if it were in left-to-right text, i.e., to the right of the preceding text.
Some software requires using the HTML code ‎ or ‎ instead of the invisible Unicode control character itself.[ citation needed ] Using the invisible control character directly could also make copy editing difficult.
A bidirectional text contains two text directionalities, right-to-left (RTL) and left-to-right (LTR). It generally involves text containing different types of alphabets, but may also refer to boustrophedon, which is changing text direction in each row.
ISO/IEC 8859-8, Information technology — 8-bit single-byte coded graphic character sets — Part 8: Latin/Hebrew alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings. ISO/IEC 8859-8:1999 from 1999 represents its second and current revision, preceded by the first edition ISO/IEC 8859-8:1988 in 1988. It is informally referred to as Latin/Hebrew. ISO/IEC 8859-8 covers all the Hebrew letters, but no Hebrew vowel signs. IBM assigned code page 916 to it. This character set was also adopted by Israeli Standard SI1311:2002, with some extensions.
ISO/IEC 8859-6:1999, Information technology — 8-bit single-byte coded graphic character sets — Part 6: Latin/Arabic alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1987. It is informally referred to as Latin/Arabic. It was designed to cover Arabic. Only nominal letters are encoded, no preshaped forms of the letters, so shaping processing is required for display. It does not include the extra letters needed to write most Arabic-script languages other than Arabic itself.
The Standard Compression Scheme for Unicode (SCSU) is a Unicode Technical Standard for reducing the number of bytes needed to represent Unicode text, especially if that text uses mostly characters from one or a small number of per-language character blocks. It does so by dynamically mapping values in the range 128–255 to offsets within particular blocks of 128 characters. The initial conditions of the encoder mean that existing strings in ASCII and ISO-8859-1 that do not contain C0 control codes other than NULL TAB CR and LF can be treated as SCSU strings. Since most alphabets do reside in blocks of contiguous Unicode codepoints, texts that use small alphabets and either ASCII punctuation or punctuation that fits within the window for the main alphabet can be encoded at one byte per character, most other punctuation can be encoded at 2 bytes per symbol through non-locking shifts. SCSU can also switch to UTF-16 internally to handle non-alphabetic languages.
The ʻokina, also called by several other names, is a unicameral consonant letter used within the Latin script to mark the phonemic glottal stop in many Polynesian languages.
Complex text layout (CTL) or complex text rendering is the typesetting of writing systems in which the shape or positioning of a grapheme depends on its relation to other graphemes. The term is used in the field of software internationalization, where each grapheme is a character.
This article provides basic comparisons for notable text editors. More feature details for text editors are available from the Category of text editor features and from the individual products' articles. This article may not be up-to-date or necessarily all-inclusive.
A code point, codepoint or code position is a unique position in a quantized n-dimensional space that has been assigned a semantic meaning.
Line breaking, also known as word wrapping, is breaking a section of text into lines so that it will fit into the available width of a page, window or other display area. In text display, line wrap is continuing on a new line when a line is full, so that each line fits into the viewable window, allowing text to be read from top to bottom without any horizontal scrolling. Word wrap is the additional feature of most text editors, word processors, and web browsers, of breaking lines between words rather than within words, where possible. Word wrap makes it unnecessary to hard-code newline delimiters within paragraphs, and allows the display of text to adapt flexibly and dynamically to displays of varying sizes.
In typography and especially computer typography, white space or whitespace is any character or series of characters that represent horizontal or vertical space. When rendered, a whitespace character does not correspond to a visible mark, but typically does occupy an area on a page. For example, the common whitespace symbol U+0020 SPACE represents a blank space punctuation character in text, used as a word divider in Western scripts.
In a right-to-left, top-to-bottom script, writing starts from the right of the page and continues to the left, proceeding from top to bottom for new lines. Arabic, Hebrew, and Adlam are the most widespread RTL writing systems in modern times.
A Hebrew keyboard comes in two different keyboard layouts. Most Hebrew keyboards are bilingual, with Latin characters, usually in a US Qwerty layout. Trilingual keyboard options also exist, with the third script being Arabic or Russian, due to the sizable Arabic- and Russian-speaking populations in Israel.
The right-to-left mark (RLM) is a non-printing character used in the computerized typesetting of bi-directional text containing a mix of left-to-right scripts and right-to-left scripts.
The Unicode Consortium and the ISO/IEC JTC 1/SC 2/WG 2 jointly collaborate on the list of the characters in the Universal Coded Character Set. The Universal Coded Character Set, most commonly called the Universal Character Set, is an international standard to map characters, discrete symbols used in natural language, mathematics, music, and other domains, to unique machine-readable data values. By creating this mapping, the UCS enables computer software vendors to interoperate, and transmit—interchange—UCS-encoded text strings from one to another. Because it is a universal map, it can be used to represent multiple languages at the same time. This avoids the confusion of using multiple legacy character encodings, which can result in the same sequence of codes having multiple interpretations depending on the character encoding in use, resulting in mojibake if the wrong one is chosen.
Many Unicode characters are used to control the interpretation or display of text, but these characters themselves have no visual or spatial representation. For example, the null character is used in C-programming application environments to indicate the end of a string of characters. In this way, these programs only require a single starting memory address for a string, since the string ends once the program reads the null character.
The Universal Coded Character Set is a standard set of characters defined by the international standard ISO/IEC 10646, Information technology — Universal Coded Character Set (UCS), which is the basis of many character encodings, improving as characters from previously unrepresented typing systems are added.
The Unicode Standard assigns various properties to each Unicode character and code point.
General Punctuation is a Unicode block containing punctuation, spacing, and formatting characters for use with all scripts and writing systems. Included are the defined-width spaces, joining formats, directional formats, smart quotes, archaic and novel punctuation such as the interrobang, and invisible mathematical operators.
The Arabic letter mark (ALM) is a non-printing character used in the computerized typesetting of bi-directional text containing mixed left-to-right scripts and right-to-left scripts.
Trojan Source is the name of a software vulnerability that abuses Unicode's bidirectional characters to display source code differently than the actual execution of the source code. The exploit utilizes how writing scripts of different reading directions are displayed and encoded on computers. It was discovered by Nicholas Boucher and Ross Anderson at Cambridge University in late 2021.
