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Code As Data
In computer science, the expression code as data refers to the idea that source code written in a programming language can be manipulated as data, such as a sequence of characters or an abstract syntax tree (AST), and it has an execution semantics only in the context of a given compiler or interpreter. The notion is often used in the context of Lisp-like languages that use S-expressions as their main syntax, as writing programs using nested lists of symbols makes the interpretation of the program as an AST quite transparent (a property known as homoiconicity). These ideas are generally used in the context of what is called metaprogramming, writing programs that treat other programs as their data. For example, code-as-data allows the serialization of first-class functions in a portable manner. Another use case is storing a program in a string, which is then processed by a compiler to produce an executable. More often there is a reflection API that exposes the structure of a progra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Source Code
In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer. Since a computer, at base, only understands machine code, source code must be Translator (computing), translated before a computer can Execution (computing), execute it. The translation process can be implemented three ways. Source code can be converted into machine code by a compiler or an assembler (computing), assembler. The resulting executable is machine code ready for the computer. Alternatively, source code can be executed without conversion via an interpreter (computing), interpreter. An interpreter loads the source code into memory. It simultaneously translates and executes each statement (computer science), statement. A method that combines compilation and interpretation is to first produce bytecode. Bytecode is an intermediate representation of source code tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computational Theory
In theoretical computer science and mathematics, the theory of computation is the branch that deals with what problems can be solved on a model of computation, using an algorithm, how efficiently they can be solved or to what degree (e.g., approximate solutions versus precise ones). The field is divided into three major branches: automata theory and formal languages, computability theory, and computational complexity theory, which are linked by the question: ''"What are the fundamental capabilities and limitations of computers?".'' In order to perform a rigorous study of computation, computer scientists work with a mathematical abstraction of computers called a model of computation. There are several models in use, but the most commonly examined is the Turing machine. Computer scientists study the Turing machine because it is simple to formulate, can be analyzed and used to prove results, and because it represents what many consider the most powerful possible "reasonable" mode ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Markup Language
A markup language is a Encoding, text-encoding system which specifies the structure and formatting of a document and potentially the relationships among its parts. Markup can control the display of a document or enrich its content to facilitate automated processing. A markup language is a set of rules governing what markup information may be included in a document and how it is combined with the content of the document in a way to facilitate use by humans and computer programs. The idea and terminology evolved from the "marking up" of paper manuscripts (e.g., with revision instructions by editors), traditionally written with a red pen or blue pencil (editing), blue pencil on authors' manuscripts. Older markup languages, which typically focus on typography and presentation, include Troff, TeX, and LaTeX. Scribe (markup language), Scribe and most modern markup languages, such as Extensible Markup Language, XML, identify document components (for example headings, paragraphs, and tabl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Domain-specific Language
A domain-specific language (DSL) is a computer language specialized to a particular application domain. This is in contrast to a general-purpose language (GPL), which is broadly applicable across domains. There are a wide variety of DSLs, ranging from widely used languages for common domains, such as HTML for web pages, down to languages used by only one or a few pieces of software, such as MUSH soft code. DSLs can be further subdivided by the kind of language, and include domain-specific ''markup'' languages, domain-specific ''modeling'' languages (more generally, specification languages), and domain-specific ''programming'' languages. Special-purpose computer languages have always existed in the computer age, but the term "domain-specific language" has become more popular due to the rise of domain-specific modeling. Simpler DSLs, particularly ones used by a single application, are sometimes informally called mini-languages. The line between general-purpose languages and doma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Configuration Scripts
A configuration file, a.k.a. config file, is a file that stores data used to configure a software system such as an application, a server or an operating system. Some applications provide a tool to create, modify, and verify the syntax of their configuration files sometimes via graphical user interface (GUI). For context, system administrators may be expected to create and modify text config files via a text editor. For server processes and operating-system settings, there is often no standard tool, but operating systems may provide graphical interfaces such as YaST or debconf. Some computer programs only read their configuration files at startup. Others periodically check the configuration files for changes. Users can instruct some programs to re-read the configuration files and apply the changes to the current process, or indeed to read arbitrary files as a configuration file. There are no definitive standards or strong conventions. RAPHICS_QUALITY HIGH_FPS=2 #0-Off, 1= ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Declarative Programming
In computer science, declarative programming is a programming paradigm—a style of building the structure and elements of computer programs—that expresses the logic of a computation without describing its control flow. Many languages that apply this style attempt to minimize or eliminate side effects by describing ''what'' the program must accomplish in terms of the problem domain, rather than describing ''how'' to accomplish it as a sequence of the programming language primitives (the ''how'' being left up to the language's implementation). This is in contrast with imperative programming, which implements algorithms in explicit steps. Declarative programming often considers programs as theories of a formal logic, and computations as deductions in that logic space. Declarative programming may greatly simplify writing parallel programs. Common declarative languages include those of database query languages (e.g., SQL, XQuery), regular expressions, logic programming ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exploit (computer Security)
An exploit is a method or piece of code that takes advantage of Vulnerability (computer security), vulnerabilities in software, Application software, applications, Computer network, networks, operating systems, or Computer hardware, hardware, typically for malicious purposes. The term "exploit" derives from the English verb "to exploit," meaning "to use something to one’s own advantage." Exploits are designed to identify flaws, bypass security measures, gain unauthorized access to systems, take control of systems, install malware, or data breach, steal sensitive data. While an exploit by itself may not be a malware, it serves as a vehicle for delivering malicious software by breaching security controls. Researchers estimate that malicious exploits cost the global economy over US$450 billion annually. In response to this threat, organizations are increasingly utilizing cyber threat intelligence to identify vulnerabilities and prevent hacks before they occur. Description Expl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Self-modifying Code
In computer science, self-modifying code (SMC or SMoC) is source code, code that alters its own instruction (computer science), instructions while it is execution (computing), executing – usually to reduce the instruction path length and improve computer performance, performance or simply to reduce otherwise duplicate code, repetitively similar code, thus simplifying software maintenance, maintenance. The term is usually only applied to code where the self-modification is intentional, not in situations where code accidentally modifies itself due to an error such as a buffer overflow. Self-modifying code can involve overwriting existing instructions or generating new code at run time and transferring control to that code. Self-modification can be used as an alternative to the method of "flag setting" and conditional program branching, used primarily to reduce the number of times a condition needs to be tested. The method is frequently used for conditionally invoking test/deb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stored Programs
A stored-program computer is a computer that stores program instructions in electronically, electromagnetically, or optically accessible memory. This contrasts with systems that stored the program instructions with plugboards or similar mechanisms. The definition is often extended with the requirement that the treatment of programs and data in memory be interchangeable or uniform. Description In principle, stored-program computers have been designed with various architectural characteristics. A computer with a von Neumann architecture stores program data and instruction data in the same memory, while a computer with a Harvard architecture has separate memories for storing program and data. However, the term ''stored-program computer'' is sometimes used as a synonym for the von Neumann architecture. Jack Copeland considers that it is "historically inappropriate, to refer to electronic stored-program digital computers as 'von Neumann machines. Hennessy and Patterson wrote that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Von Neumann Architecture
The von Neumann architecture—also known as the von Neumann model or Princeton architecture—is a computer architecture based on the '' First Draft of a Report on the EDVAC'', written by John von Neumann in 1945, describing designs discussed with John Mauchly and J. Presper Eckert at the University of Pennsylvania's Moore School of Electrical Engineering. The document describes a design architecture for an electronic digital computer made of "organs" that were later understood to have these components: * A processing unit with both an arithmetic logic unit and processor registers * A control unit that includes an instruction register and a program counter * Memory that stores data and instructions * External mass storage * Input and output mechanisms.. The attribution of the invention of the architecture to von Neumann is controversial, not least because Eckert and Mauchly had done a lot of the required design work and claim to have had the idea for stored programs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kleene's Second Recursion Theorem
In computability theory, Kleene's recursion theorems are a pair of fundamental results about the application of computable functions to their own descriptions. The theorems were first proved by Stephen Kleene in 1938 and appear in his 1952 book ''Introduction to Metamathematics''. A related theorem, which constructs fixed points of a computable function, is known as Rogers's theorem and is due to Hartley Rogers, Jr. The recursion theorems can be applied to construct fixed points of certain operations on computable functions, to generate quines, and to construct functions defined via recursive definitions. Notation The statement of the theorems refers to an admissible numbering \varphi of the partial recursive functions, such that the function corresponding to index e is \varphi_e. If F and G are partial functions on the natural numbers, the notation F \simeq G indicates that, for each ''n'', either F(n) and G(n) are both defined and are equal, or else F(n) and G(n) ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reflection (computer Programming)
In computer science, reflective programming or reflection is the ability of a process to examine, introspect, and modify its own structure and behavior. Historical background The earliest computers were programmed in their native assembly languages, which were inherently reflective, as these original architectures could be programmed by defining instructions as data and using self-modifying code. As the bulk of programming moved to higher-level compiled languages such as ALGOL, COBOL, Fortran, Pascal, and C, this reflective ability largely disappeared until new programming languages with reflection built into their type systems appeared. Brian Cantwell Smith's 1982 doctoral dissertation introduced the notion of computational reflection in procedural programming languages and the notion of the meta-circular interpreter as a component of 3-Lisp. Uses Reflection helps programmers make generic software libraries to display data, process different formats of data, perform s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
