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Null Function
In computer science, a null function (or null operator) is a subroutine that leaves the program state unchanged. When it is part of the instruction set of a processor, it is called a NOP or NOOP (No OPeration). Mathematically, a (computer) function f is null if and only if its execution leaves the program state s unchanged. That is, a null function is an identity function whose domain and codomain are both the state space S of the program, and for which: f(s)=s for all elements s \in S. Less rigorous definitions may also be encountered. For example, a function may take a single operand, transform it into a new data type, and return the result.Example of a type conversion function labeled as a "null function"_NULLF - null function./ref> While such usages bear a strong visual resemblance to identity functions, they create or alter a binary data value and thus change the program state. From a software maintainability perspective it is better to identify such "minor" alternation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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] |
Software Development
Software development is the process of designing and Implementation, implementing a software solution to Computer user satisfaction, satisfy a User (computing), user. The process is more encompassing than Computer programming, programming, writing source code, code, in that it includes conceiving the goal, evaluating feasibility, analyzing software requirements, requirements, software design, design, software testing, testing and software release life cycle, release. The process is part of software engineering which also includes management, organizational management, Software project management, project management, configuration management and other aspects. Software development involves many skills and job specializations including software programmer, programming, software test, testing, Technical writing, documentation, graphic design, user support, marketing, and fundraising. Software development involves many software tools, tools including: compiler, integrated develo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IEFBR14
IEFBR14 is a utility program that runs on mainframe computers from IBM. It runs in all mainframe environments derived from OS/360, including z/OS. It is a placeholder that returns the exit status zero, similar to the true command on UNIX-like systems. Purpose Allocation (also called Initiation) On OS/360 and derived mainframe systems, most programs never specify files (usually called datasets) directly, but instead reference them indirectly through the Job Control Language (JCL) statements that invoke the programs. These data definition (or "DD") statements can include a "disposition" (DISP=...) parameter that indicates how the file is to be managed — whether a new file is to be created or an old one re-used; and whether the file should be deleted upon completion or retained; ''etc''. IEFBR14 was created because while DD statements can create or delete files easily, they cannot do so without a program to be run due to a certain peculiarity of the Job Management system, w ... [...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 exampl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating System
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for efficient use of the system and may also include accounting software for cost allocation of Scheduling (computing), processor time, mass storage, peripherals, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computerfrom cellular phones and video game consoles to web servers and supercomputers. , Android (operating system), Android is the most popular operating system with a 46% market share, followed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiprocessing
Multiprocessing (MP) is the use of two or more central processing units (CPUs) within a single computer system. The term also refers to the ability of a system to support more than one processor or the ability to allocate tasks between them. There are many variations on this basic theme, and the definition of multiprocessing can vary with context, mostly as a function of how CPUs are defined ( multiple cores on one die, multiple dies in one package, multiple packages in one system unit, etc.). A multiprocessor is a computer system having two or more processing units (multiple processors) each sharing main memory and peripherals, in order to simultaneously process programs. A 2009 textbook defined multiprocessor system similarly, but noted that the processors may share "some or all of the system’s memory and I/O facilities"; it also gave tightly coupled system as a synonymous term. At the operating system level, ''multiprocessing'' is sometimes used to refer to the executi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Software Applications
Application software is any computer program that is intended for end-user use not operating, administering or programming the computer. An application (app, application program, software application) is any program that can be categorized as application software. Common types of applications include word processor, media player and accounting software. The term ''application software'' refers to all applications collectively and can be used to differentiate from system and utility software. Applications may be bundled with the computer and its system software or published separately. Applications may be proprietary or open-source. The short term ''app'' (coined in 1981 or earlier) became popular with the 2008 introduction of the iOS App Store, to refer to applications for mobile devices such as smartphones and tablets. Later, with introduction of the Mac App Store (in 2010) and Windows Store (in 2011), the term was extended in popular use to include desktop applications ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embedded System Overview
An embedded system is a specialized computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is embedded as part of a complete device often including electrical or electronic hardware and mechanical parts. Because an embedded system typically controls physical operations of the machine that it is embedded within, it often has real-time computing constraints. Embedded systems control many devices in common use. , it was estimated that ninety-eight percent of all microprocessors manufactured were used in embedded systems. Modern embedded systems are often based on microcontrollers (i.e. microprocessors with integrated memory and peripheral interfaces), but ordinary microprocessors (using external chips for memory and peripheral interface circuits) are also common, especially in more complex systems. In either case, the processor(s) used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
