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Dynamic Software Updating
In computer science, dynamic software updating (DSU) is a field of research pertaining to upgrading programs while they are running. DSU is not currently widely used in industry. However, researchers have developed a wide variety of systems and techniques for implementing DSU. These systems are commonly tested on real-world programs. Current operating systems and programming languages are typically not designed with DSU in mind. As such, DSU implementations commonly either utilize existing tools, or implement specialty compilers. These compilers preserve the semantics of the original program, but instrument either the source code or object code to produce a dynamically updateable program. Researchers compare DSU-capable variants of programs to the original program to assess safety and performance overhead. Introduction Any running program can be thought of a tuple (\delta, P), where \delta is the current program state and P is the current program code. Dynamic software updating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical disciplines (including the design and implementation of Computer architecture, hardware and Computer programming, software). Computer science is generally considered an area of research, academic research and distinct from computer programming. 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 for preventing Vulnerability (computing), security vulnerabilities. Computer graphics (computer science), Computer graphics and computational geometry address the generation of images. Progr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Redis
Redis (; Remote Dictionary Server) is an in-memory data structure store, used as a distributed, in-memory key–value database, cache and message broker, with optional durability. Redis supports different kinds of abstract data structures, such as strings, lists, maps, sets, sorted sets, HyperLogLogs, bitmaps, streams, and spatial indices. The project was developed and maintained by Salvatore Sanfilippo, starting in 2009. From 2015 until 2020, he led a project core team sponsored by Redis Labs. Salvatore Sanfilippo left Redis as the maintainer in 2020. It is open-source software released under a BSD 3-clause license. In 2021, not long after the original author and main maintainer left, Redis Labs dropped the Labs from its name and now is known simply as "Redis". History The name Redis means Remote Dictionary Server. The Redis project began when Salvatore Sanfilippo, nicknamed ''antirez'', the original developer of Redis, was trying to improve the scalability of his Italian ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canonical Form
In mathematics and computer science, a canonical, normal, or standard form of a mathematical object is a standard way of presenting that object as a mathematical expression. Often, it is one which provides the simplest representation of an object and which allows it to be identified in a unique way. The distinction between "canonical" and "normal" forms varies from subfield to subfield. In most fields, a canonical form specifies a ''unique'' representation for every object, while a normal form simply specifies its form, without the requirement of uniqueness. The canonical form of a positive integer in decimal representation is a finite sequence of digits that does not begin with zero. More generally, for a class of objects on which an equivalence relation is defined, a canonical form consists in the choice of a specific object in each class. For example: *Jordan normal form is a canonical form for matrix similarity. *The row echelon form is a canonical form, when one considers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Runtime (computing)
In computer science, runtime, run time, or execution time is the final phase of a computer programs life cycle, in which the code is being executed on the computer's central processing unit (CPU) as machine code. In other words, "runtime" is the running phase of a program. A runtime error is detected after or during the execution (running state) of a program, whereas a compile-time error is detected by the compiler before the program is ever executed. Type checking, register allocation, code generation, and code optimization are typically done at compile time, but may be done at runtime depending on the particular language and compiler. Many other runtime errors exist and are handled differently by different programming languages, such as division by zero errors, domain errors, array subscript out of bounds errors, arithmetic underflow errors, several types of underflow and overflow errors, and many other runtime errors generally considered as software bugs which may or may ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Self-modifying Code
In computer science, self-modifying code (SMC) is code that alters its own instructions while it is executing – usually to reduce the instruction path length and improve performance or simply to reduce otherwise repetitively similar code, thus simplifying 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/debugging code without requiring additional computational overhead for every input/output cycle. The modifications may be performed: * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Load-time
In computing, computer systems a loader is the part of an operating system that is responsible for loading computer program, programs and Library (computing), libraries. It is one of the essential stages in the process of starting a program, as it places programs into memory and prepares them for execution. Loading a program involves memory-mapped file, memory-mapping the contents of the executable, executable file containing the program instructions into memory, and then carrying out other required preparatory tasks to prepare the executable for running. Once loading is complete, the operating system starts the program by passing control to the loaded program code. All operating systems that support program loading have loaders, apart from highly specialized computer systems that only have a fixed set of specialized programs. Embedded systems typically do not have loaders, and instead, the code executes directly from ROM or similar. In order to load the operating system itself, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relocation (computing)
Relocation is the process of assigning load addresses for position-dependent code and data of a program and adjusting the code and data to reflect the assigned addresses. Prior to the advent of multiprocess systems, and still in many embedded systems, the addresses for objects were absolute starting at a known location, often zero. Since multiprocessing systems dynamically link and switch between programs it became necessary to be able to relocate objects using position-independent code. A linker usually performs relocation in conjunction with symbol resolution, the process of searching files and libraries to replace symbolic references or names of libraries with actual usable addresses in memory before running a program. Relocation is typically done by the linker at link time, but it can also be done at load time by a relocating loader, or at run time by the running program itself. Some architectures avoid relocation entirely by deferring address assignment to run time; as, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Dead Code Elimination
In compiler theory, dead-code elimination (also known as DCE, dead-code removal, dead-code stripping, or dead-code strip) is a compiler optimization to remove code which does not affect the program results. Removing such code has several benefits: it shrinks program size, an important consideration in some contexts, and it allows the running program to avoid executing irrelevant operations, which reduces its running time. It can also enable further optimizations by simplifying program structure. ''Dead code'' includes code that can never be executed (''unreachable code''), and code that only affects ''dead variables'' (written to, but never read again), that is, irrelevant to the program. Examples Consider the following example written in C (programming language), C. int foo(void) Simple analysis of the uses of values would show that the value of b after the first assignment is not used inside foo. Furthermore, b is declared as a local variable inside foo, so its value cannot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unreachable Code
In computer programming, unreachable code is part of the source code of a program which can never be executed because there exists no control flow path to the code from the rest of the program. Unreachable code is sometimes also called ''dead code'', although dead code may also refer to code that is executed but has no effect on the output of a program. Unreachable code is generally considered undesirable for several reasons: * It uses memory unnecessarily * It can cause unnecessary use of the CPU's instruction cache ** This can also decrease data locality * Time and effort may be spent testing, maintaining and documenting code which is never used ** Sometimes an automated test is the only thing using the code. However, unreachable code can have some legitimate uses, like providing a library of functions for calling or jumping to manually via a debugger while the program is halted after a breakpoint. This is particularly useful for examining and pretty-printing the internal state ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dead Code
The term dead code has multiple definitions. Some use the term to refer to code (i.e. instructions in memory) which can never be executed at run-time. In some areas of computer programming, dead code is a section in the source code of a program which is executed but whose result is never used in any other computation. The execution of dead code wastes computation time and memory. While the result of a dead computation may never be used, it may raise exceptions or affect some global state, thus removal of such code may change the output of the program and introduce unintended bugs. Compiler optimizations are typically conservative in their approach to dead-code removal if there is any ambiguity as to whether removal of the dead code will affect the program output. The programmer may aid the compiler in this matter by making additional use of static and/or inline functions and enabling the use of link-time optimization. Example int foo (int iX, int iY) In the above example, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Dead-code Elimination
In compiler theory, dead-code elimination (also known as DCE, dead-code removal, dead-code stripping, or dead-code strip) is a compiler optimization to remove code which does not affect the program results. Removing such code has several benefits: it shrinks program size, an important consideration in some contexts, and it allows the running program to avoid executing irrelevant operations, which reduces its running time. It can also enable further optimizations by simplifying program structure. ''Dead code'' includes code that can never be executed (''unreachable code''), and code that only affects '' dead variables'' (written to, but never read again), that is, irrelevant to the program. Examples Consider the following example written in C. int foo(void) Simple analysis of the uses of values would show that the value of b after the first assignment is not used inside foo. Furthermore, b is declared as a local variable inside foo, so its value cannot be used outside foo. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backward-compatible
Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially in telecommunications and computing. Modifying a system in a way that does not allow backward compatibility is sometimes called " breaking" backward compatibility. A complementary concept is forward compatibility. A design that is forward-compatible usually has a roadmap for compatibility with future standards and products. A related term from programming jargon is hysterical reasons or hysterical raisins (near-homophones for "historical reasons"), as the purpose of some software features may be solely to support older hardware or software versions. Usage In hardware A simple example of both backward and forward compatibility is the introduction of FM radio in stereo. FM radio was initially mono, with only one audio channel represented ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
