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Reinterpret Cast
In computer science, a type punning is any programming technique that subverts or circumvents the type system of a programming language in order to achieve an effect that would be difficult or impossible to achieve within the bounds of the formal language. In C and C++, constructs such as pointer type conversion and union — C++ adds reference type conversion and reinterpret_cast to this list — are provided in order to permit many kinds of type punning, although some kinds are not actually supported by the standard language. In the Pascal programming language, the use of records with variants may be used to treat a particular data type in more than one manner, or in a manner not normally permitted. Sockets example One classic example of type punning is found in the Berkeley sockets interface. The function to bind an opened but uninitialized socket to an IP address is declared as follows: int bind(int sockfd, struct sockaddr *my_addr, socklen_t addrlen); The bind fu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Pointer (computer Programming)
In computer science, a pointer is an object in many programming languages that stores a memory address. This can be that of another value located in computer memory, or in some cases, that of memory-mapped computer hardware. A pointer ''references'' a location in memory, and obtaining the value stored at that location is known as ''dereferencing'' the pointer. As an analogy, a page number in a book's index could be considered a pointer to the corresponding page; dereferencing such a pointer would be done by flipping to the page with the given page number and reading the text found on that page. The actual format and content of a pointer variable is dependent on the underlying computer architecture. Using pointers significantly improves performance for repetitive operations, like traversing iterable data structures (e.g. strings, lookup tables, control tables, linked lists, and tree structures). In particular, it is often much cheaper in time and space to copy and deref ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Computer Science
Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, applied disciplines (including the design and implementation of Computer architecture, hardware and Software engineering, software). Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of computational problem, problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and preventing security vulnerabilities. Computer graphics (computer science), Computer graphics and computational geometry address the generation of images. Programming language theory considers different ways to describe computational processes, and database theory concerns the management of re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Sign Bit
In computer science, the sign bit is a bit in a signed number representation that indicates the sign of a number. Although only signed numeric data types have a sign bit, it is invariably located in the most significant bit position, so the term may be used interchangeably with "most significant bit" in some contexts. Almost always, if the sign bit is 0, the number is non-negative (positive or zero). If the sign bit is 1 then the number is negative. Formats other than two's complement integers allow a signed zero: distinct "positive zero" and "negative zero" representations, the latter of which does not correspond to the mathematical concept of a negative number. When using a complement representation, to convert a signed number to a wider format the additional bits must be filled with copies of the sign bit in order to preserve its numerical value, a process called '' sign extension'' or ''sign propagation''. Sign bit weight in Two's complement Two's complement is by far th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Unspecified Behavior
In computer programming, unspecified behavior is behavior that may vary on different implementations of a programming language. A program can be said to contain unspecified behavior when its source code may produce an executable that exhibits different behavior when compiled on a different compiler, or on the same compiler with different settings, or indeed in different parts of the same executable. While the respective language standards or specifications may impose a range of possible behaviors, the exact behavior depends on the implementation and may not be completely determined upon examination of the program's source code.ISO/IEC (2009-05-29). ''ISO/IEC PDTR 24772.2: Guidance to Avoiding Vulnerabilities in Programming Languages through Language Selection and Use'' Unspecified behavior will often not manifest itself in the resulting program's external behavior, but it may sometimes lead to differing outputs or results, potentially causing portability problems. Definition To ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Strict Aliasing
In computing, aliasing describes a situation in which a data location in memory can be accessed through different symbolic names in the program. Thus, modifying the data through one name implicitly modifies the values associated with all aliased names, which may not be expected by the programmer. As a result, aliasing makes it particularly difficult to understand, analyze and optimize programs. Aliasing analysers intend to make and compute useful information for understanding aliasing in programs. Aliased pointers Aliasing can occur in any language that can refer to one location in memory with more than one name (for example, with pointers). This is a common problem with functions that accept pointer arguments, and their tolerance (or the lack thereof) for aliasing must be carefully documented, particularly for functions that perform complex manipulations on memory areas passed to them. Specified aliasing Controlled aliasing behaviour may be desirable in some cases (that is, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Undefined Behavior
In computer programming, a program exhibits undefined behavior (UB) when it contains, or is executing code for which its programming language specification does not mandate any specific requirements. This is different from unspecified behavior, for which the language specification does not prescribe a result, and implementation-defined behavior that defers to the documentation of another component of the platform (such as the ABI or the translator documentation). In the C programming community, undefined behavior may be humorously referred to as "nasal demons", after a comp.std.c post that explained undefined behavior as allowing the compiler to do anything it chooses, even "to make demons fly out of your nose". Overview Some programming languages allow a program to operate differently or even have a different control flow from the source code, as long as it exhibits the same user-visible side effects, ''if undefined behavior never happens during program execution''. Undef ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Aliasing (computing)
In computing, aliasing describes a situation in which a data location in memory can be accessed through different symbolic names in the program. Thus, modifying the data through one name implicitly modifies the values associated with all aliased names, which may not be expected by the programmer. As a result, aliasing makes it particularly difficult to understand, analyze and optimize programs. Aliasing analysers intend to make and compute useful information for understanding aliasing in programs. Aliased pointers Aliasing can occur in any language that can refer to one location in memory with more than one name (for example, with pointers). This is a common problem with functions that accept pointer arguments, and their tolerance (or the lack thereof) for aliasing must be carefully documented, particularly for functions that perform complex manipulations on memory areas passed to them. Specified aliasing Controlled aliasing behaviour may be desirable in some cases (that is, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Data Structure Alignment
Data structure alignment is the way data is arranged and accessed in computer memory. It consists of three separate but related issues: data alignment, data structure padding, and packing. The CPU in modern computer hardware performs reads and writes to memory most efficiently when the data is ''naturally aligned'', which generally means that the data's memory address is a multiple of the data size. For instance, in a 32-bit architecture, the data may be aligned if the data is stored in four consecutive bytes and the first byte lies on a 4-byte boundary. ''Data alignment'' is the aligning of elements according to their natural alignment. To ensure natural alignment, it may be necessary to insert some ''padding'' between structure elements or after the last element of a structure. For example, on a 32-bit machine, a data structure containing a 16-bit value followed by a 32-bit value could have 16 bits of ''padding'' between the 16-bit value and the 32-bit value to align the 3 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Quake III
''Quake III Arena'' is a 1999 first-person shooter game developed by id Software. The third installment of the ''Quake'' series, ''Arena'' differs from previous games by excluding a story-based single-player mode and focusing primarily on multiplayer gameplay. The single-player mode is played against computer-controlled bots. It features music composed by Sonic Mayhem and Front Line Assembly founder Bill Leeb. Notable features of ''Quake III Arena'' include a minimalist design, very extensively customizable settings such as field of view, texture detail and enemy model; and advanced movement features such as strafe-jumping and rocket-jumping. The game was praised by reviewers who, for the most part, described the gameplay as fun and engaging. Many liked the crisp graphics and focus on multiplayer. ''Quake III Arena'', often being considered one of the greatest video games ever made, has also been used extensively in professional electronic sports tournaments such as Quak ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
