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Null Device
In some operating systems, the null device is a device file that discards all data written to it but reports that the write operation succeeded. This device is called /dev/null on Unix and Unix-like systems, NUL: (see TOPS-20) or NUL on CP/M and DOS (internally \DEV\NUL), nul on OS/2 and newer Windows systems (internally \Device\Null on Windows NT), NIL: on Amiga operating systems, and NL: on OpenVMS. In Windows Powershell, the equivalent is $null. It provides no data to any process that reads from it, yielding EOF immediately. In IBM operating systems DOS/360 and successors and also in OS/360 and successors such files would be assigned in JCL to DD DUMMY. In programmer jargon, especially Unix jargon, it may also be called the bit bucket or black hole. History is described as an empty regular file in Version 4 Unix. The Version 5 Unix manual describes a device with modern semantics. Usage The null device is typically used for disposing of unwanted output streams of ... [...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] |
Z/OS
z/OS is a 64-bit operating system for IBM z/Architecture mainframes, introduced by IBM in October 2000. It derives from and is the successor to OS/390, which in turn was preceded by a string of MVS versions.Starting with the earliest: * OS/VS2 Release 2 through Release 3.8 * MVS/System Extensions (MVS/SE) * MVS/System Product (MVS/SP) Version 1 * MVS/System Product Version 2 (MVS/Extended Architecture, MVS/XA) * MVS/System Product Version 3 (MVS/Enterprise Systems Architecture, MVS/ESA) * MVS/ESA SP Version 4 * MVS/ESA SP Version 5 Like OS/390, z/OS combines a number of formerly separate, related products, some of which are still optional. z/OS has the attributes of modern operating systems but also retains much of the older functionality that originated in the 1960s and is still in regular use—z/OS is designed for backward compatibility. Major characteristics z/OS supportsSome, e.g., TSO/E, are bundled with z/OS, others, e.g., CICS, are separately priced. stable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jargon
Jargon, or technical language, is the specialized terminology associated with a particular field or area of activity. Jargon is normally employed in a particular Context (language use), communicative context and may not be well understood outside that context. The context is usually a particular occupation (that is, a certain trade, profession, vernacular or academic field), but any ingroups and outgroups, ingroup can have jargon. The key characteristic that distinguishes jargon from the rest of a language is its specialized vocabulary, which includes terms and definitions of words that are unique to the context, and terms used in a narrower and more exact sense than when used in colloquial language. This can lead In-group and out-group, outgroups to misunderstand communication attempts. Jargon is sometimes understood as a form of technical slang and then distinguished from the official terminology used in a particular field of activity. The terms ''jargon'', ''slang,'' and ''argot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mv (Unix)
mv is a shell command for renaming and moving files and directories. If both items are on the same file system, the command renames; otherwise items are copied to the destination and the old items are removed (more specifically unlinked). To move between two directories, the user must have write permission for both because the command modifies the content of both. For a rename, an item's timestamp is not modified. On Unix implementations derived from AT&T Unix, cp, ln and mv are implemented as a single program with hard-linked binaries. History Multics provided a file move/rename command named . A version with the contracted name appeared in Version 1 Unix and became part of the X/Open Portability Guide issue 2 of 1987. The version in GNU Core Utilities was written by Mike Parker, David MacKenzie, and Jim Meyering. The command is available in Windows via UnxUtils. The command was ported to IBM i. Options Most implementations support: * -i interactive; the comma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Directory (file Systems)
Directory may refer to: * Directory (computing), or folder, a file system structure in which to store computer files * Directory (OpenVMS command) * Directory service, a software application for organizing information about a computer network's users and resources * Directory (political), a system under which a country is ruled by a college of several people who jointly exercise the powers of a head of state or head of government ** French Directory The Directory (also called Directorate; ) was the system of government established by the Constitution of the Year III, French Constitution of 1795. It takes its name from the committee of 5 men vested with executive power. The Directory gov ..., the government in revolutionary France from 1795 to 1799 ** Provisional All-Russian Government, a short-lived, anti-Communist government formed during the Russian Civil War, known as "the Directory" * Business directory, a listing of information about suppliers and manufacturers * Ci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Device File
In Unix-like operating systems, a device file, device node, or special file is an interface to a device driver that appears in a file system as if it were an ordinary file. There are also special files in DOS, OS/2, and Windows. These special files allow an application program to interact with a device by using its device driver via standard input/output system calls. Using standard system calls simplifies many programming tasks, and leads to consistent user-space I/O mechanisms regardless of device features and functions. Overview Device files usually provide simple interfaces to standard devices (such as printers and serial ports), but can also be used to access specific unique resources on those devices, such as disk partitions. Additionally, device files are useful for accessing system resources that have no connection with any actual device, such as data sinks and random number generators. There are two general kinds of device files in Unix-like operating syst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tar (computing)
In computing, tar is a shell command for combining multiple computer files into a single archive file. It was originally developed for magnetic tape storage reading and writing data for a sequential I/O device with no file system, and the name is short for the format description "tape archive". When stored in a file system, a file that tar reads and writes is often called a ''tarball''. A tarball contains metadata for the contained files including the name, ownership, timestamps, permissions and directory organization. As a file containing other files with associated metadata, a tarball is useful for software distribution and backup. POSIX abandoned ''tar'' in favor of '' pax'', yet ''tar'' continues to have widespread use. History The command was introduced to Unix in January 1979, replacing the tp program (which in turn replaced "tap"). The file structure was standardized in POSIX.1-1988 and later POSIX.1-2001, and became a format supported by most modern file ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Redirection (computing)
In computing, redirection is a form of interprocess communication, and is a function common to most command-line interpreters, including the various Unix shells that can redirect standard streams to user-specified locations. The concept of redirection is quite old, dating back to the earliest operating systems (OS). A discussion of the design goals for redirection can be found already in the 1971 description of the input-output subsystem of the Multics OS. However, prior to the introduction of UNIX OS with its "pipes", redirection in operating systems was hard or even impossible to do. In Unix-like operating systems, programs do redirection with the system call, or its less-flexible but higher-level stdio analogues, and . Redirecting standard input and standard output Redirection is usually implemented by placing certain characters between commands. Basic Typically, the syntax of these characters is as follows, using < to redirect input, and > to redirect output. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer File
A computer file is a System resource, resource for recording Data (computing), data on a Computer data storage, computer storage device, primarily identified by its filename. Just as words can be written on paper, so too can data be written to a computer file. Files can be shared with and transferred between computers and Mobile device, mobile devices via removable media, Computer networks, networks, or the Internet. Different File format, types of computer files are designed for different purposes. A file may be designed to store a written message, a document, a spreadsheet, an Digital image, image, a Digital video, video, a computer program, program, or any wide variety of other kinds of data. Certain files can store multiple data types at once. By using computer programs, a person can open, read, change, save, and close a computer file. Computer files may be reopened, modified, and file copying, copied an arbitrary number of times. Files are typically organized in a file syst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stream (computing)
In computer science, a stream is a sequence of potentially unlimited data elements made available over time. A stream can be thought of as items on a conveyor belt being processed one at a time rather than in large batches. Streams are processed differently from batch data. Normal functions cannot operate on streams as a whole because they have potentially unlimited data. Formally, streams are '' codata'' (potentially unlimited), not data (which is finite). Functions that operate on a stream producing another stream are known as filters and can be connected in pipelines in a manner analogous to function composition. Filters may operate on one item of a stream at a time or may base an item of output on multiple items of input such as a moving average. Examples The term "stream" is used in a number of similar ways: * "Stream editing", as with sed, awk, and perl. Stream editing processes a file or files, in-place, without having to load the file(s) into a user interface. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Version 5 Unix
Research Unix refers to the early versions of the Unix operating system for DEC PDP-7, PDP-11, VAX and Interdata 7/32 and 8/32 computers, developed in the Bell Labs Computing Sciences Research Center (CSRC). The term ''Research Unix'' first appeared in the Bell System Technical Journal (Vol. 57, No. 6, Part 2 July/August 1978) to distinguish it from other versions internal to Bell Labs (such as PWB/UNIX and MERT) whose code-base had diverged from the primary CSRC version. However, that term was little-used until Version 8 Unix (1985), but has been retroactively applied to earlier versions as well. Prior to V8, the operating system was most commonly called simply UNIX (in caps) or the UNIX Time-Sharing System. Ancient UNIX is any early release of the Unix code base prior to Unix System III, particularly the Research Unix releases prior to and including Version 7 (the base for UNIX/32V as well as later developments of AT&T Unix). History AT&T licensed Version 5 to edu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Version 4 Unix
Research Unix refers to the early versions of the Unix operating system for PDP-7, DEC PDP-7, PDP-11, VAX and Interdata 7/32 and 8/32 computers, developed in the Bell Labs Computing Sciences Research Center (CSRC). The term ''Research Unix'' first appeared in the Bell System Technical Journal (Vol. 57, No. 6, Part 2 July/August 1978) to distinguish it from other versions internal to Bell Labs (such as PWB/UNIX and Multi-Environment Real-Time, MERT) whose code-base had diverged from the primary CSRC version. However, that term was little-used until Version 8 Unix (1985), but has been Retroactive continuity, retroactively applied to earlier versions as well. Prior to V8, the operating system was most commonly called simply UNIX (in caps) or the UNIX Time-Sharing System. Ancient UNIX is any early release of the Unix code base prior to Unix System III, particularly the Research Unix releases prior to and including Version 7 (the base for UNIX/32V as well as later developments of AT&T Un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
