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Katherine Johnson’s mathematical calculations helped guide some of America’s most important early space missions while she confronted the racial and gender barriers faced by Black women in twentieth-century America.
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This is a personal recollection on the Move fire on May 13, 1985
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The Universal Coded Character Set (UCS, Unicode) is a standard set of characters defined by the international standard ISO/IEC 10646, Information technology — Universal Coded Character Set (UCS) (plus amendments to that standard), which is the basis of many character encodings, improving as characters from previously unrepresented writing systems are added.[1]
The UCS has over 1.1 million possible code points available for use/allocation, but only the first 65,536, which is the Basic Multilingual Plane (BMP), had entered into common use before 2000. This situation began changing when the People's Republic of China (PRC) ruled in 2006 that all software sold in its jurisdiction would have to support GB 18030. This required software intended for sale in the PRC to move beyond the BMP.[clarification needed][2]
The system deliberately leaves many code points not assigned to characters, even in the BMP. It does this to allow for future expansion or to minimise conflicts with other encoding forms.
The original edition of the UCS defined UTF-16, an extension of UCS-2, to represent code points outside the BMP. A range of code points in the S (Special) Zone of the BMP remains unassigned to characters. UCS-2 disallows use of code values for these code points, but UTF-16 allows their use in pairs. Unicode also adopted UTF-16, but in Unicode terminology, the high-half zone elements become "high surrogates" and the low-half zone elements become "low surrogates".[clarification needed]
Another encoding, UTF-32 (previously named UCS-4), uses four bytes (total 32 bits) to encode a single character of the codespace. UTF-32 thereby permits a binary representation of every code point (as of year 2024) in the APIs, and software applications.
The International Organization for Standardization (ISO) set out to compose the universal character set in 1989, and published the draft of ISO 10646 in 1990. Hugh McGregor Ross was one of its principal architects.
This work happened independently of the development of the Unicode standard, which had been in development since 1987 by Xerox and Apple.
The original ISO 10646 draft differed markedly from the current standard. It defined:
for an apparent total of 2,147,483,648 characters, but actually the standard could code only 679,477,248 characters, as the policy forbade byte values of C0 and C1 control codes (0x00 to 0x1F and 0x80 to 0x9F, in hexadecimal notation) in any one of the four bytes specifying a group, plane, row and cell. The Latin capital letter A, for example, had a location in group 0x20, plane 0x20, row 0x20, cell 0x41.
One could code the characters of this primordial ISO/IEC 10646 standard in one of three ways:
In 1990, therefore, two initiatives for a universal character set existed: Unicode, with 16 bits for every character (65,536 possible characters), and ISO/IEC 10646. The software companies refused to accept the complexity and size requirement of the ISO standard and were able to convince a number of ISO National Bodies to vote against it.[citation needed] ISO officials realised they could not continue to support the standard in its current state and negotiated the unification of their standard with Unicode. Two changes took place: the lifting of the limitation upon characters (prohibition of control code values), thus opening code points for allocation; and the synchronisation of the repertoire of the Basic Multilingual Plane with that of Unicode.
Meanwhile, in the passage of time, the situation changed in the Unicode standard itself: 65,536 characters came to appear insufficient, and the standard from version 2.0 and onwards supports encoding of 1,112,064 code points from 17 planes by means of the UTF-16 surrogate mechanism. For that reason, ISO/IEC 10646 was limited to contain as many characters as could be encoded by UTF-16 and no more, that is, a little over a million characters instead of over 679 million. The UCS-4 encoding of ISO/IEC 10646 was incorporated into the Unicode standard with the limitation to the UTF-16 range and under the name UTF-32, although it has almost no use outside programs' internal data.
Rob Pike and Ken Thompson, the designers of the Plan 9 operating system, devised a new, fast and well-designed mixed-width encoding that was also backward-compatible with 7-bit ASCII, which came to be called UTF-8,[3] and is currently the most popular UCS encoding.
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ISO/IEC 10646 and Unicode have an identical repertoire and numbers—the same characters with the same numbers exist on both standards, although Unicode releases new versions and adds new characters more often. Unicode has rules and specifications outside the scope of ISO/IEC 10646. ISO/IEC 10646 is a simple character map, an extension of previous standards like ISO/IEC 8859. In contrast, Unicode adds rules for collation, normalisation of forms, and the bidirectional algorithm for right-to-left scripts such as Arabic and Hebrew. For interoperability between platforms, especially if bidirectional scripts are used, it is not enough to support ISO/IEC 10646; Unicode must be implemented.
To support these rules and algorithms, Unicode adds many properties to each character in the set such as properties determining a character's default bidirectional class and properties to determine how the character combines with other characters. If the character represents a numeric value such as the European number '8', or the vulgar fraction '¼', that numeric value is also added as a property of the character. Unicode intends these properties to support interoperable text handling with a mixture of languages.
Some applications support ISO/IEC 10646 characters but do not fully support Unicode. One such application, Xterm, can properly display all ISO/IEC 10646 characters that have a one-to-one character-to-glyph mapping[clarification needed] and a single directionality. It can handle some combining marks by simple overstriking methods, but cannot display Hebrew (bidirectional), Devanagari (one character to many glyphs) or Arabic (both features). Most GUI applications use standard OS text drawing routines which handle such scripts, although the applications themselves still do not always handle them correctly.
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ISO/IEC 10646, a general, informal citation for the ISO/IEC 10646 family of standards, is acceptable in most prose. And even though it is a separate standard, the term Unicode is used just as often, informally, when discussing the UCS. However, any normative references to the UCS as a publication should cite the year of the edition in the form ISO/IEC 10646:{year}, for example: ISO/IEC 10646:2014.
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Since 1991, the Unicode Consortium and the ISO/IEC have developed The Unicode Standard ("Unicode") and ISO/IEC 10646 in tandem. The repertoire, character names, and code points of Unicode Version 2.0 exactly match those of ISO/IEC 10646-1:1993 with its first seven published amendments. After Unicode 3.0 was published in February 2000, corresponding new and updated characters entered the UCS via ISO/IEC 10646-1:2000. In 2003, parts 1 and 2 of ISO/IEC 10646 were combined into a single part, which has since had a number of amendments adding characters to the standard in approximate synchrony with the Unicode standard.
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Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
The Universal Coded Character Set (UCS, Unicode) is a standard set of characters defined by the international standard ISO/IEC 10646, Information technology — Universal Coded Character Set (UCS) (plus amendments to that standard), which is the basis of many character encodings, improving as characters from previously unrepresented writing systems are added. The UCS has over 1.1 million possible code points available for use/allocation, but only the first 65,536, which is the Basic Multilingual Plane (BMP), had entered into common use before 2000. This situation began changing when the People's Republic of China (PRC) ruled in 2006 that all software sold in its jurisdiction would have to support GB 18030. This required software intended for sale in the PRC to move beyond the BMP. The system deliberately leaves many code points not assigned to characters, even in the BMP. It does this to allow for future expansion or to minimise conflicts with other encoding forms. The original edition of the UCS defined UTF-16, an extension of UCS-2, to represent code points outside the BMP. A range of code points in the S (Special) Zone of the BMP remains unassigned to characters. UCS-2 disallows use of code values for these code points, but UTF-16 allows their use in pairs. Unicode also adopted UTF-16, but in Unicode terminology, the high-half zone elements become "high surrogates" and the low-half zone elements become "low surrogates". Another encoding, UTF-32 (previously named UCS-4), uses four bytes (total 32 bits) to encode a single character of the codespace. UTF-32 thereby permits a binary representation of every code point (as of year 2024) in the APIs, and software applications.
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 (abbr. UCS, official designation: ISO/IEC 10646), 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. UCS has a potential capacity of over 1 million characters. Each UCS character is abstractly represented by a code point, an integer between 0 and 1,114,111 (1,114,112 = 220 + 216 or 17 × 216 = 0x110000 code points), used to represent each character within the internal logic of text processing software. As of Unicode 18.0, released in September 2026, 316,784 (28%) of these code points are allocated, 172,873 (15%) have been assigned characters, 137,468 (12%) are reserved for private use, 2,048 are used to enable the mechanism of surrogates, and 66 are designated as noncharacters, leaving the remaining 797,328 (72%) unallocated. The number of encoded characters is made up as follows: 172,636 graphical characters (some of which do not have a visible glyph, but are still counted as graphical) 237 special purpose characters for control and formatting. ISO maintains the basic mapping of characters from character name to code point. Often, the terms character and code point will be used interchangeably. However, when a distinction is made, a code point refers to the integer of the character: what one might think of as its address. Meanwhile, a character in ISO/IEC 10646 includes the combination of the code point and its name, Unicode adds many other useful properties to the character set, such as block, category, script, and directionality. In addition to the UCS, the supplementary Unicode Standard, (not a joint project with ISO, but rather a publication of the Unicode Consortium,) provides other implementation details such as: mappings between UCS and other character sets different collations of characters and character strings for different languages an algorithm for laying out bidirectional text ("the BiDi algorithm"), where text on the same line may shift between left-to-right ("LTR") and right-to-left ("RTL") a case-folding algorithm Computer software end users enter these characters into programs through various input methods, for example, physical keyboards or virtual character palettes. The UCS can be divided in various ways, such as by plane, block, character category, or character property.
The Universal Character Set (Universal Coded Character Set, UCS, Unicode) is a standard set of characters defined by the international standard ISO/IEC 10646, Information technology — Universal Coded Character Set (UCS) (plus amendments to that standard), which is the basis of many character encodings, improving as characters from previously unrepresented typing systems are added. Universal Character Set can also refer to Universal Character Set feature for impact printers
The null character is a control character with the value zero. Many character sets include a code point for a null character – including Unicode (Universal Coded Character Set), ASCII (ISO/IEC 646), Baudot, ITA2 codes, the C0 control code, and EBCDIC. In modern character sets, the null character has a code point value of zero which is generally translated to a single code unit with a zero value. For instance, in UTF-8, it is a single, zero byte. Originally, its meaning was like NOP – when sent to a printer or a terminal, it had no effect (although some terminals incorrectly displayed it as space). When electromechanical teleprinters were used as computer output devices, one or more null characters were sent at the end of each printed line to allow time for the mechanism to return to the first printing position on the next line. On punched tape, the character is represented with no holes at all, so a new unpunched tape is initially filled with null characters, and often text could be inserted at a reserved space of null characters by punching the new characters into the tape over the nulls. A null-terminated string is a commonly used data structure in the C programming language, its many derivative languages and other programming contexts that uses a null character to indicate the end of a string. This design allows a string to be any length at the cost of only one extra character of memory. The common competing design for a string stores the length of the string as an integer data type, but this limits the size of the string to the range of the integer (for example, 255 for a byte). For byte storage, the null character can be called a null byte.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Mae Jemison, aboard Space Shuttle Endeavour in 1992.
