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Eqn (software)
Part of the troff suite of Unix document layout tools, eqn is a preprocessor that formats equations for printing. A similar program, neqn, accepted the same input as eqn, but produced output tuned to look better in nroff. The eqn program was created in 1974 by Brian Kernighan and Lorinda Cherry. It was implemented using yacc compiler-compiler. The input language used by eqn allows the user to write mathematical expressions in much the same way as they would be spoken aloud. The language is defined by a context-free grammar, together with operator precedence and operator associativity rules. The eqn language is similar to the mathematical component of TeX, which appeared several years later, but is simpler and less complete. An independent compatible implementation of the eqn preprocessor has been developed by GNU as part of groff, the GNU version of troff. The GNU implementation extends the original language by adding a number of new keywords such as ''smallover'' and ''a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brian Kernighan
Brian Wilson Kernighan (; born 1942) is a Canadian computer scientist. He worked at Bell Labs and contributed to the development of Unix alongside Unix creators Ken Thompson and Dennis Ritchie. Kernighan's name became widely known through co-authorship of the first book on the C programming language (''The C Programming Language'') with Dennis Ritchie. Kernighan affirmed that he had no part in the design of the C language ("it's entirely Dennis Ritchie's work"). He authored many Unix programs, including ditroff. Kernighan is coauthor of the AWK and AMPL programming languages. The "K" of K&R C and of AWK both stand for "Kernighan". In collaboration with Shen Lin he devised well-known heuristics for two NP-complete optimization problems: graph partitioning and the travelling salesman problem. In a display of authorial equity, the former is usually called the Kernighan–Lin algorithm, while the latter is known as the Lin–Kernighan heuristic. Kernighan has been a Professor of C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nroff
nroff (short for "new roff") is a text-formatting program on Unix and Unix-like operating systems. It produces output suitable for simple fixed-width printers and terminal windows. It is an integral part of the Unix help system, being used to format man pages for display. nroff and the related troff were both developed from the original roff. While nroff was intended to produce output on terminals and line printers, troff was intended to produce output on typesetting systems. Both used the same underlying markup and a single source file could normally be used by nroff or troff without change. History nroff was written by Joe Ossanna for Version 2 Unix, in Assembly language and then ported to C. It was a descendant of the RUNOFF program from CTSS, the first computerized text-formatting program, and is a predecessor of the Unix troff document processing system. There is also a free software version of nroff in the groff package. Variants The Minix operating system, among ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communications Of The ACM
''Communications of the ACM'' is the monthly journal of the Association for Computing Machinery (ACM). It was established in 1958, with Saul Rosen as its first managing editor. It is sent to all ACM members. Articles are intended for readers with backgrounds in all areas of computer science and information systems. The focus is on the practical implications of advances in information technology and associated management issues; ACM also publishes a variety of more theoretical journals. The magazine straddles the boundary of a science magazine, trade magazine, and a scientific journal. While the content is subject to peer review, the articles published are often summaries of research that may also be published elsewhere. Material published must be accessible and relevant to a broad readership. From 1960 onward, ''CACM'' also published algorithms, expressed in ALGOL. The collection of algorithms later became known as the Collected Algorithms of the ACM. See also * ''Journal of the A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whitespace Character
In computer programming, whitespace is any character or series of characters that represent horizontal or vertical space in typography. 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 (also ASCII 32) represents a blank space punctuation character in text, used as a word divider in Western scripts. Overview With many keyboard layouts, a whitespace character may be entered by pressing . Horizontal whitespace may also be entered on many keyboards with the key, although the length of the space may vary. Vertical whitespace may be input by typing , which creates a 'newline' code sequence in most programs. On older keyboards, this key may instead be labeled , a holdover from typewriter keyboards' carriage return keys, which generated an electromechanical return to the left stop (Unicode character ) and a move to the next line (). Many early computer games used whitesp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lexical Analysis
In computer science, lexical analysis, lexing or tokenization is the process of converting a sequence of characters (such as in a computer program or web page) into a sequence of ''lexical tokens'' (strings with an assigned and thus identified meaning). A program that performs lexical analysis may be termed a ''lexer'', ''tokenizer'', or ''scanner'', although ''scanner'' is also a term for the first stage of a lexer. A lexer is generally combined with a parser, which together analyze the syntax of programming languages, web pages, and so forth. Applications A lexer forms the first phase of a compiler frontend in modern processing. Analysis generally occurs in one pass. In older languages such as ALGOL, the initial stage was instead line reconstruction, which performed unstropping and removed whitespace and comments (and had scannerless parsers, with no separate lexer). These steps are now done as part of the lexer. Lexers and parsers are most often used for compilers, but ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Man Pages
A man page (short for manual page) is a form of software documentation usually found on a Unix or Unix-like operating system. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts. A user may invoke a man page by issuing the man command. By default, man typically uses a terminal pager program such as more or less to display its output. Man pages are often referred to as an ''on-line'' or ''online'' form of software documentation, * even though the man command does not require internet access, dating back to the times when printed ''out-of-band'' manuals were the norm. History In the first two years of the history of Unix, no documentation existed. The Unix Programmer's Manual' was first published on November 3, 1971. The first actual man pages were written by Dennis Ritchie and Ken Thompson at the insistence of their manager Doug McIlroy in 1971. Aside from the man pages, the ''Programmer' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mandoc
mandoc (historically called mdocml) is a utility used for formatting man pages in BSD Operating Systems (e.g. NetBSD), specifically those written in the ''mdoc'' and ''man'' macro languages. Unlike the groff and older troff and nroff tools that are predominantly used for this purpose by tools such as , mandoc focuses specifically on manuals and is not suitable for general-purpose type-setting. is mainly used to format the ''mdoc'' manuals used in the BSD Operating Systems, but it also implements most of the ''man'' macros used in Linux distributions, as well as a subset of roff commands occasionally intermixed with the ''man'' macros. It does not support other macro sets such as ''mm'' and ''ms'', or any typesetting features like hyphenation, fonts and alignment. Simple styling such as bold and italics are supported, but italicized text is replaced by underlined text on the terminal. mandoc has built-in support for the troff soelim (inclusion) preprocessor and partial built ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keyword (computer Programming)
Keyword may refer to: Computing * Keyword (Internet search), a word or phrase typically used by bloggers or online content creator to rank a web page on a particular topic * Index term, a term used as a keyword to documents in an information system such as a catalog or a search engine * Keyword advertising, a form of online advertising * Keyword clustering, a search engine optimization technique * A reserved word in a programming language Other * Keyword (linguistics), word which occurs in a text more often than we would expect to occur by chance alone * Keyword (rhetoric) Keywords are the words that academics use to reveal the internal structure of an author's reasoning. While they are used primarily for rhetoric, they are also used in a strictly grammatical sense for structural composition, reasoning, and compre ..., a word that academics use to reveal the internal structure of an author's reasoning * '' Keywords: A Vocabulary of Culture and Society'', 1973 non-fiction book ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Groff (software)
Groff ( ) (also called GNU troff) is a typesetting system that creates formatted output when given plain text mixed with formatting commands. It is the GNU replacement for the troff and nroff text formatters. Groff contains a large number of helper programs, preprocessors, and postprocessors including eqn, tbl, pic and soelim. There are also several macro packages included that duplicate, expand on the capabilities of, or outright replace the standard troff macro packages. Groff development of new features is active, and is an important part of free, open source, and UNIX derived operating systems such as Linux and 4.4BSD derivatives — notably because troff macros are used to create man pages, the standard form of documentation on Unix and Unix-like systems. OpenBSD has replaced groff with mandoc in the base install, since their 4.9 release. Also macOS Ventura. History groff is an original implementation written primarily in C++ by James Clark and is modeled aft ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operator Associativity
In programming language theory, the associativity of an operator is a property that determines how operators of the same precedence are grouped in the absence of parentheses. If an operand is both preceded and followed by operators (for example, ^ 3 ^), and those operators have equal precedence, then the operand may be used as input to two different operations (i.e. the two operations indicated by the two operators). The choice of which operations to apply the operand to, is determined by the associativity of the operators. Operators may be associative (meaning the operations can be grouped arbitrarily), left-associative (meaning the operations are grouped from the left), right-associative (meaning the operations are grouped from the right) or non-associative (meaning operations cannot be chained, often because the output type is incompatible with the input types). The associativity and precedence of an operator is a part of the definition of the programming language; different p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operator Precedence
In mathematics and computer programming, the order of operations (or operator precedence) is a collection of rules that reflect conventions about which procedures to perform first in order to evaluate a given mathematical expression. For example, in mathematics and most computer languages, multiplication is granted a higher precedence than addition, and it has been this way since the introduction of modern algebraic notation. Thus, the expression is interpreted to have the value , and not . When exponents were introduced in the 16th and 17th centuries, they were given precedence over both addition and multiplication, and could be placed only as a superscript to the right of their base. Thus and . These conventions exist to eliminate notational ambiguity, while allowing notation to be as brief as possible. Where it is desired to override the precedence conventions, or even simply to emphasize them, parentheses ( ) can be used. For example, forces addition to precede multiplic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Context-free Grammar
In formal language theory, a context-free grammar (CFG) is a formal grammar whose production rules are of the form :A\ \to\ \alpha with A a ''single'' nonterminal symbol, and \alpha a string of terminals and/or nonterminals (\alpha can be empty). A formal grammar is "context-free" if its production rules can be applied regardless of the context of a nonterminal. No matter which symbols surround it, the single nonterminal on the left hand side can always be replaced by the right hand side. This is what distinguishes it from a context-sensitive grammar. A formal grammar is essentially a set of production rules that describe all possible strings in a given formal language. Production rules are simple replacements. For example, the first rule in the picture, :\langle\text\rangle \to \langle\text\rangle = \langle\text\rangle ; replaces \langle\text\rangle with \langle\text\rangle = \langle\text\rangle ;. There can be multiple replacement rules for a given nonterminal symbol. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
