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M4 (computer Language)
m4 is a general-purpose macro processor included in most Unix-like operating systems, and is a component of the POSIX standard. The language was designed by Brian Kernighan and Dennis Ritchie for the original versions of UNIX. It is an extension of an earlier macro processor, m3, written by Ritchie for an unknown AP-3 minicomputer.Brian W. Kernighan and Dennis M. Ritchie. The m4 macro processor. Technical report, Bell Laboratories, Murray Hill, New Jersey, USA, 1977pdf/ref> The macro preprocessor operates as a text-replacement tool. It is employed to re-use text templates, typically in computer programming applications, but also in text editing and text-processing applications. Most users require m4 as a dependency of GNU autoconf. History Macro processors became popular when programmers commonly used assembly language. In those early days of programming, programmers noted that much of their programs consisted of repeated text, and they invented simple means for reusing this tex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macro (computer Science)
In computer programming, a macro (short for "macro instruction"; ) is a rule or pattern that specifies how a certain input should be mapped to a replacement output. Applying a macro to an input is known as macro expansion. The input and output may be a sequence of lexical tokens or characters, or a syntax tree. Character macros are supported in software applications to make it easy to invoke common command sequences. Token and tree macros are supported in some programming languages to enable code reuse or to extend the language, sometimes for domain-specific languages. Macros are used to make a sequence of computing instructions available to the programmer as a single program statement, making the programming task less tedious and less error-prone. (Thus, they are called "macros" because a "big" block of code can be expanded from a "small" sequence of characters.) Macros often allow positional or keyword parameters that dictate what the conditional assembler program generates ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ratfor
Ratfor (short for ''Rational Fortran'') is a programming language implemented as a preprocessor for Fortran 66. It provides modern control structures, unavailable in Fortran 66, to replace GOTOs and statement numbers. Features Ratfor provides the following kinds of flow-control statements, described by Kernighan and Plauger as "shamelessly stolen from the language C, developed for the UNIX operating system by D.M. Ritchie" ("Software Tools", p. 318): * statement grouping with braces * if-else, while, for, do, repeat-until, break, next * "free-form" statements, i.e., not constrained by Fortran format rules * , >=, ... in place of .LT., .GT., .GE., ... * include * # comments For example, the following code if (a > b) else might be translated as IF(.NOT.(A.GT.B))GOTO 1 MAX = A GOTO 2 1 CONTINUE MAX = B 2 CONTINUE The version of Ratfor in ''Software Tools'' is written in Ratfor, as are the sample programs, and inasmuch as its own trans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apostrophe
The apostrophe ( or ) is a punctuation mark, and sometimes a diacritical mark, in languages that use the Latin alphabet and some other alphabets. In English, the apostrophe is used for two basic purposes: * The marking of the omission of one or more letters, e.g. the contraction of "do not" to "don't". * The marking of possessive case of nouns (as in "the eagle's feathers", "in one month's time", "at your parents' ome). The word "apostrophe" comes ultimately from Greek (, ' he accent ofturning away or elision'), through Latin and French. For use in computer systems, Unicode has code points for three different forms of apostrophe. Usage in English Historical development The apostrophe was first used by Pietro Bembo in his edition of '' De Aetna'' (1496). It was introduced into English in the 16th century in imitation of French practice. French practice Introduced by Geoffroy Tory (1529), the apostrophe was used in place of a vowel letter to indicate elision (as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delimiter
A delimiter is a sequence of one or more characters for specifying the boundary between separate, independent regions in plain text, mathematical expressions or other data streams. An example of a delimiter is the comma character, which acts as a ''field delimiter'' in a sequence of comma-separated values. Another example of a delimiter is the time gap used to separate letters and words in the transmission of Morse code. In mathematics, delimiters are often used to specify the scope of an operation, and can occur both as isolated symbols (e.g., colon in "1 : 4") and as a pair of opposing-looking symbols (e.g., angled brackets in \langle a, b \rangle). Delimiters represent one of various means of specifying boundaries in a data stream. Declarative notation, for example, is an alternate method that uses a length field at the start of a data stream to specify the number of characters that the data stream contains. describing the method in Hollerith notation under the Fortran p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backtick
The backtick is a typographical mark used mainly in computing. It is also known as backquote, grave, or grave accent. The character was designed for typewriters to add a grave accent to a (lower-case) base letter, by overtyping it atop that letter. On early computer systems, however, this physical dead key+overtype function was rarely supported, being functionally replaced by precomposed characters. Consequently, this ASCII symbol was rarely (if ever) used in computer systems for its original aim and became repurposed for many unrelated uses in computer programming. The sign is located on the left-top of a US or UK layout keyboard, next to the key. On older keyboards the Escape key was at this location, and the backtick key was somewhere on the right side of the layout. Provision (if any) of the backtick on other keyboards varies by national keyboard layout and keyboard mapping. History Typewriters On typewriters designed for languages that routinely use diacritics (accent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turing-complete
In computability theory, a system of data-manipulation rules (such as a computer's instruction set, a programming language, or a cellular automaton) is said to be Turing-complete or computationally universal if it can be used to simulate any Turing machine (devised by English mathematician and computer scientist Alan Turing). This means that this system is able to recognize or decide other data-manipulation rule sets. Turing completeness is used as a way to express the power of such a data-manipulation rule set. Virtually all programming languages today are Turing-complete. A related concept is that of Turing equivalence two computers P and Q are called equivalent if P can simulate Q and Q can simulate P. The Church–Turing thesis conjectures that any function whose values can be computed by an algorithm can be computed by a Turing machine, and therefore that if any real-world computer can simulate a Turing machine, it is Turing equivalent to a Turing machine. A universal Turi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free-form Language
In computer programming, a free-form language is a programming language in which the positioning of characters on the page in program text is insignificant. Program text does not need to be placed in specific columns as on old punched card systems, and frequently ends of lines are insignificant. Whitespace characters are used only to delimit tokens, and have no other significance. Most free-form languages descend from ALGOL, including C, Pascal, and Perl. Lisp languages are free-form, although they do not descend from ALGOL. Rexx is mostly free-form, though in some cases whitespace characters are concatenation operators. SQL, though not a full programming language, is also free-form. Most free-form languages are also structured programming languages, which is sometimes thought to go along with the free-form syntax: Earlier imperative programming languages such as Fortran 77 used particular columns for line numbers, which many structured languages do not use or need. Structu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Automatic Programming
In computer science, the term automatic programming identifies a type of computer programming in which some mechanism generates a computer program to allow human programmers to write the code at a higher abstraction level. There has been little agreement on the precise definition of automatic programming, mostly because its meaning has changed over time. David Parnas, tracing the history of "automatic programming" in published research, noted that in the 1940s it described automation of the manual process of punching paper tape. Later it referred to translation of high-level programming languages like Fortran and ALGOL. In fact, one of the earliest programs identifiable as a compiler was called Autocode. Parnas concluded that "automatic programming has always been a euphemism for programming in a higher-level language than was then available to the programmer." Program synthesis is one type of automatic programming where a procedure is created from scratch, based on mathematic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SELinux
Security-Enhanced Linux (SELinux) is a Linux kernel security module that provides a mechanism for supporting access control security policies, including mandatory access controls (MAC). SELinux is a set of kernel modifications and user-space tools that have been added to various Linux distributions. Its architecture strives to separate enforcement of security decisions from the security policy, and streamlines the amount of software involved with security policy enforcement. The key concepts underlying SELinux can be traced to several earlier projects by the United States National Security Agency (NSA). Overview The NSA Security-enhanced Linux Team describes NSA SELinux as a set of patches to the Linux kernel and utilities to provide a strong, flexible, mandatory access control (MAC) architecture into the major subsystems of the kernel. It provides an enhanced mechanism to enforce the separation of information based on confidentiality and integrity requirements, which allows ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GEDA
The term gEDA refers to two things: # A set of software applications (CAD tools) used for electronic design released under the GPL. As such, gEDA is an ECAD (electronic CAD) or EDA (electronic design automation) application suite. gEDA is mostly oriented towards printed circuit board design (as opposed to integrated circuit design). The gEDA applications are often referred to collectively as "the gEDA Suite". # The collaboration of free software/open-source developers who work to develop and maintain the gEDA toolkit. The developers communicate via gEDA mailing lists, and have participated in the annual "Google Summer of Code" event as a single project. This collaboration is often referred to as "the gEDA Project". The word "gEDA" is a conjunction of "GPL" and "EDA". The names of some of the individual tools in the gEDA Suite are prefixed with the letter "g" to emphasize that they are released under the GNU General Public License. History The gEDA project was started ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
