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Backslash
The backslash is a mark used mainly in computing and mathematics. It is the mirror image of the common slash (punctuation), slash . It is a relatively recent mark, first documented in the 1930s. It is sometimes called a hack, whack, Escape character, escape (from C (programming language), C/UNIX), reverse slash, slosh, downwhack, backslant, backwhack, bash, reverse slant, reverse solidus, and reversed virgule. History , efforts to identify either the origin of this character or its purpose before the 1960s have not been successful. The earliest known reference found to date is a 1937 maintenance manual from the Teletype Corporation with a photograph showing the keyboard of its Kleinschmidt keyboard perforator WPE-3 using the Wheatstone system. The symbol was called the "diagonal key", and given a (non-standard) Morse code of . In June 1960, IBM published an "Extended character set standard" that includes the symbol at 0x19. Referencing Computer Standards Collection, Arch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
String Literal
string literal or anonymous string is a literal for a string value in the source code of a computer program. Modern programming languages commonly use a quoted sequence of characters, formally "bracketed delimiters", as in x = "foo", where , "foo" is a string literal with value foo. Methods such as escape sequences can be used to avoid the problem of delimiter collision (issues with brackets) and allow the delimiters to be embedded in a string. There are many alternate notations for specifying string literals especially in complicated cases. The exact notation depends on the programming language in question. Nevertheless, there are general guidelines that most modern programming languages follow. Syntax Bracketed delimiters Most modern programming languages use bracket delimiters (also balanced delimiters) to specify string literals. Double quotations are the most common quoting delimiters used: "Hi There!" An empty string is literally written by a pair of quotes with n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slash (punctuation)
The slash is a slanting line punctuation mark . It is also known as a stroke, a solidus, a forward slash and #Alternative names, several other historical or technical names. Once used as the equivalent of the modern full stop, period and comma, the slash is now used to represent #Division, division and #Fractions, fractions, as a #Dating, date separator, or to connect alternative terms. A slash in the reverse direction is known as a backslash. History Slashes may be found in early writing as a variant form of dash (typography), dashes, vertical bar, vertical strokes, etc. The present use of a slash distinguished from such other marks derives from the medieval European #virgule, virgule (, which was used as a full stop, period, #scratch, scratch comma, and caesura mark. (The first sense was eventually lost to the full stop, low dot and the other two developed separately into the comma and caesura mark ) Its use as a comma became especially widespread in Kingdom of France, Fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Escape Character
In computing and telecommunications, an escape character is a character that invokes an alternative interpretation on the following characters in a character sequence. An escape character is a particular case of metacharacters. Generally, the judgement of whether something is an escape character or not depends on the context. In the telecommunications field, escape characters are used to indicate that the following characters are encoded differently. This is used to alter control characters that would otherwise be noticed and acted on by the underlying telecommunications hardware, such as illegal characters. In this context, the use of escape characters is often referred to as quoting. Definition An escape character may not have its own meaning, so all escape sequences are of two or more characters. Escape characters are part of the syntax for many programming languages, data formats, and communication protocols. For a given alphabet an escape character's purpose is to star ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regular Expression
A regular expression (shortened as regex or regexp), sometimes referred to as rational expression, is a sequence of characters that specifies a match pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings, or for input validation. Regular expression techniques are developed in theoretical computer science and formal language theory. The concept of regular expressions began in the 1950s, when the American mathematician Stephen Cole Kleene formalized the concept of a regular language. They came into common use with Unix text-processing utilities. Different syntaxes for writing regular expressions have existed since the 1980s, one being the POSIX standard and another, widely used, being the Perl syntax. Regular expressions are used in search engines, in search and replace dialogs of word processors and text editors, in text processing utilities such as sed and AWK, and in lexical analysis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
JSON
JSON (JavaScript Object Notation, pronounced or ) is an open standard file format and electronic data interchange, data interchange format that uses Human-readable medium and data, human-readable text to store and transmit data objects consisting of name–value pairs and array data type, arrays (or other serialization, serializable values). It is a commonly used data format with diverse uses in electronic data interchange, including that of web applications with server (computing), servers. JSON is a Language-independent specification, language-independent data format. It was derived from JavaScript, but many modern programming languages include code to generate and parse JSON-format data. JSON filenames use the extension .json. Douglas Crockford originally specified the JSON format in the early 2000s. Transcript: He and Chip Morningstar sent the first JSON message in April 2001. Naming and pronunciation The 2017 international standard (ECMA-404 and ISO/IEC 21778:2017) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metacharacter
A metacharacter is a character that has a special meaning to a computer program, such as a shell interpreter or a regular expression (regex) engine. In POSIX extended regular expressions, there are 14 metacharacters that must be ''escaped'' — preceded by a backslash (\) — in order to drop their special meaning and be treated literally inside an expression: opening and closing square brackets ( and ">/code> and /code>); backslash (\); caret (^); dollar sign ($); period/full stop/dot (.); vertical bar/pipe symbol (, ); question mark (?); asterisk (*); plus and minus signs (+ and -); opening and closing curly brackets/braces (); and opening and closing parentheses (( and )). For example, to match the arithmetic expression (1+1)*3=6 with a regex, the correct regex is \(1\+1\)\*3=6; otherwise, the parentheses, plus sign, and asterisk will have special meanings. Other examples Some other characters may have special meaning in some environments. * In some Unix shells the semicolo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Python (programming Language)
Python is a high-level programming language, high-level, general-purpose programming language. Its design philosophy emphasizes code readability with the use of significant indentation. Python is type system#DYNAMIC, dynamically type-checked and garbage collection (computer science), garbage-collected. It supports multiple programming paradigms, including structured programming, structured (particularly procedural programming, procedural), object-oriented and functional programming. It is often described as a "batteries included" language due to its comprehensive standard library. Guido van Rossum began working on Python in the late 1980s as a successor to the ABC (programming language), ABC programming language, and he first released it in 1991 as Python 0.9.0. Python 2.0 was released in 2000. Python 3.0, released in 2008, was a major revision not completely backward-compatible with earlier versions. Python 2.7.18, released in 2020, was the last release of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bob Bemer
Robert William Bemer (February 8, 1920 – June 22, 2004) was a computer scientist best known for his work at IBM during the late 1950s and early 1960s. Early life and education Born in Sault Ste. Marie, Michigan, Bemer graduated from Cranbrook Kingswood School in 1936 and took a Bachelor of Arts (B.A.) in mathematics at Albion College in 1940. He earned a certificate in aeronautical engineering at Curtiss-Wright Technical Institute in 1941. Career Bemer began his career as an aerodynamicist at Douglas Aircraft Company in 1941, then worked for RAND Corporation from 1951, IBM from 1957, UNIVAC – Sperry Rand in 1965, Bull from 1965, General Electric from 1970, and Honeywell from 1974. He served on the committee which amalgamated the design for his COMTRAN language with Grace Hopper's FLOW-MATIC and thus produced the specifications for COBOL. He also served, with Hugh McGregor Ross and others, on the separate committee which defined the ASCII character codeset in 1960, c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ASCII
ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control characters a total of 128 code points. The set of available punctuation had significant impact on the syntax of computer languages and text markup. ASCII hugely influenced the design of character sets used by modern computers; for example, the first 128 code points of Unicode are the same as ASCII. ASCII encodes each code-point as a value from 0 to 127 storable as a seven-bit integer. Ninety-five code-points are printable, including digits ''0'' to ''9'', lowercase letters ''a'' to ''z'', uppercase letters ''A'' to ''Z'', and commonly used punctuation symbols. For example, the letter is represented as 105 (decimal). Also, ASCII specifies 33 non-printing control codes which originated with ; most of which are now obsolete. The control cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Logical Disjunction
In logic, disjunction (also known as logical disjunction, logical or, logical addition, or inclusive disjunction) is a logical connective typically notated as \lor and read aloud as "or". For instance, the English language sentence "it is sunny or it is warm" can be represented in logic using the disjunctive formula S \lor W , assuming that S abbreviates "it is sunny" and W abbreviates "it is warm". In classical logic, disjunction is given a truth functional semantics according to which a formula \phi \lor \psi is true unless both \phi and \psi are false. Because this semantics allows a disjunctive formula to be true when both of its disjuncts are true, it is an ''inclusive'' interpretation of disjunction, in contrast with exclusive disjunction. Classical proof theoretical treatments are often given in terms of rules such as disjunction introduction and disjunction elimination. Disjunction has also been given numerous non-classical treatments, motivated by problems ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unix
Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others. Initially intended for use inside the Bell System, AT&T licensed Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including University of California, Berkeley ( BSD), Microsoft (Xenix), Sun Microsystems ( SunOS/ Solaris), HP/ HPE ( HP-UX), and IBM ( AIX). The early versions of Unix—which are retrospectively referred to as " Research Unix"—ran on computers such as the PDP-11 and VAX; Unix was commonly used on minicomputers and mainframes from the 1970s onwards. It distinguished itself from its predecessors as the first portable operating system: almost the entire operating system is written in the C programming language (in 1973), which allows U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
