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Standard Streams
In computer programming, standard streams are preconnected input and output communication channels between a computer program and its environment when it begins execution. The three input/output (I/O) connections are called standard input (stdin), standard output (stdout) and standard error (stderr). Originally I/O happened via a physically connected system console (input via keyboard, output via monitor), but standard streams abstract this. When a command is executed via an interactive shell, the streams are typically connected to the text terminal on which the shell is running, but can be changed with redirection or a pipeline. More generally, a child process inherits the standard streams of its parent process. Application Users generally know standard streams as input and output channels that handle data coming from an input device, or that write data from the application. The data may be text with any encoding, or binary data. When a program is run as a daemon, its stan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Programming
Computer programming or coding is the composition of sequences of instructions, called computer program, programs, that computers can follow to perform tasks. It involves designing and implementing algorithms, step-by-step specifications of procedures, by writing source code, code in one or more programming languages. Programmers typically use high-level programming languages that are more easily intelligible to humans than machine code, which is directly executed by the central processing unit. Proficient programming usually requires expertise in several different subjects, including knowledge of the Domain (software engineering), application domain, details of programming languages and generic code library (computing), libraries, specialized algorithms, and Logic#Formal logic, formal logic. Auxiliary tasks accompanying and related to programming include Requirements analysis, analyzing requirements, Software testing, testing, debugging (investigating and fixing problems), imple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Punch Card Reader
A computer punched card reader or just computer card reader is a computer input device used to read computer programs in either source or executable form and data from punched cards. A computer card punch is a computer output device that punches holes in cards. Sometimes computer punch card readers were combined with computer card punches and, later, other devices to form multifunction machines. History Many early computers, such as the ENIAC, and the IBM NORC, provided for punched card input/output. Card readers and punches, either connected to computers or in off-line card to/from magnetic tape configurations, were ubiquitous through the mid-1970s. Punched cards had been in use since the 1890s; their technology was mature and reliable. Card readers and punches developed for punched card machines were readily adaptable for computer use. Businesses were familiar with storing data on punched cards and keypunch machines were widely employed. Punched cards were a better fit th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keyboard (computing)
A computer keyboard is a built-in or peripheral input device modeled after the typewriter keyboard which uses an arrangement of buttons or Push-button, keys to act as Mechanical keyboard, mechanical levers or Electronic switching system, electronic switches. Replacing early punched cards and paper tape technology, interaction via teleprinter-style keyboards have been the main input device, input method for computers since the 1970s, supplemented by the computer mouse since the 1980s, and the touchscreen since the 2000s. Keyboard keys (buttons) typically have a set of characters Engraving, engraved or Printing, printed on them, and each press of a key typically corresponds to a single written symbol. However, producing some symbols may require pressing and holding several keys simultaneously or in sequence. While most keys produce character (computing), characters (Letter (alphabet), letters, Numerical digit, numbers or symbols), other keys (such as the escape key) can prompt the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudoterminal
In some operating systems, including Unix-like systems, a pseudoterminal, pseudotty, or PTY is a pair of pseudo-device endpoints (files) which establish an asynchronous, bidirectional communication (IPC) channel (with two ports) between two or more processes. One pseudo-device in the pair, the ''master'', provides means by which a terminal emulator or remote login server (e.g. a Telnet, rlogin, or Secure Shell server) process controls the slave. The other pseudo-device, the ''slave'', emulates a hardware serial port device, and is used by terminal-oriented programs such as shells (e.g. bash) as a processes to read/write data back from/to ''master'' endpoint. PTYs are similar to bidirectional pipes. Devpts is a Linux kernel virtual file system containing pseudoterminal devices. Linux implementation is based on System V-style terminals (commonly referred as UNIX 98 pseudoterminals) and provides POSIX and the Single Unix Specification API in the form of a function since 1998. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Terminal
A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. Most early computers only had a front panel to input or display bits and had to be connected to a terminal to print or input text through a keyboard. Teleprinters were used as early-day hard-copy terminals and predated the use of a computer screen by decades. The computer would typically transmit a line of data which would be printed on paper, and accept a line of data from a keyboard over a serial or other interface. Starting in the mid-1970s with microcomputers such as the Sphere 1, Sol-20, and Apple I, display circuitry and keyboards began to be integrated into personal and workstation computer systems, with the computer handling character generation and outputting to a CRT display such as a computer monitor or, sometimes, a consumer TV, but most larger computers continued to require terminal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Command-line Interface
A command-line interface (CLI) is a means of interacting with software via command (computing), commands each formatted as a line of text. Command-line interfaces emerged in the mid-1960s, on computer terminals, as an interactive and more user-friendly alternative to the non-interactive mode available with punched cards. For a long time, a CLI was the most common interface for software, but today a graphical user interface (GUI) is more common. Nonetheless, many programs such as operating system and software development utility software, utilities still provide CLI. A CLI enables automation, automating computer program, programs since commands can be stored in a scripting language, script computer file, file that can be used repeatedly. A script allows its contained commands to be executed as group; as a program; as a command. A CLI is made possible by command-line interpreters or command-line processors, which are programs that execute input commands. Alternatives to a CLI ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dir (command)
dir, short for ''directory'', is a shell (computing), shell command (computing), command for listing file system contents; computer file, files and file directory, directories. Arguably, the command provides the same essential functionality as the ls command, but typically the two commands are described as notably separate concepts, possibly since is implemented from a codebase that shares more history than many implementations. The command is often implemented as internal in the operating system shell (computing), shell instead of as a separate application as many other commands are. Implementations Although syntax, semantics and implementations vary, a command is available in the command-line interface (CLI) of the operating systems Digital Research CP/M, MP/M, Intel ISIS (operating system), ISIS-II, RMX (operating system), iRMX 86, Cromemco Cromemco DOS, CDOS, MetaComCo TRIPOS, DOS, IBM/Toshiba 4690 Operating System, 4690 OS, IBM OS/2, Microsoft Windows, Singularity (op ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
COMMAND
Command may refer to: Computing * Command (computing), a statement in a computer language * command (Unix), a Unix command * COMMAND.COM, the default operating system shell and command-line interpreter for DOS * Command key, a modifier key on Apple Macintosh computer keyboards * Command pattern, a software design pattern in which objects represent actions * Voice command, in speech recognition Military * Military command (instruction) or military order * Command responsibility, the doctrine of hierarchical accountability in cases of war crimes * Command (military formation), an organizational unit * Command and control, the exercise of authority in a military organization * Command hierarchy, a group of people dedicated to carrying out orders "from the top" Music * ''Command'' (album), a 2009 album by Client * Command Records, a record label Sports * Command (baseball), the ability of a pitcher to throw a pitch where he intends to * Kansas City Command, a former profess ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C (programming Language)
C (''pronounced'' '' – like the letter c'') is a general-purpose programming language. It was created in the 1970s by Dennis Ritchie and remains very widely used and influential. By design, C's features cleanly reflect the capabilities of the targeted Central processing unit, CPUs. It has found lasting use in operating systems code (especially in Kernel (operating system), kernels), device drivers, and protocol stacks, but its use in application software has been decreasing. C is commonly used on computer architectures that range from the largest supercomputers to the smallest microcontrollers and embedded systems. A successor to the programming language B (programming language), B, C was originally developed at Bell Labs by Ritchie between 1972 and 1973 to construct utilities running on Unix. It was applied to re-implementing the kernel of the Unix operating system. During the 1980s, C gradually gained popularity. It has become one of the most widely used programming langu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Job Control Language
Job Control Language (JCL) is a scripting language used on IBM mainframe operating systems to instruct the system on how to run a batch processing, batch job or start a subsystem. The purpose of JCL is to say which programs to run, using which files or devices for input or output, and at times to also indicate under what conditions to skip a step. Parameters in the JCL can also provide accounting information for tracking the resources used by a job as well as which machine the job should run on. There are two distinct IBM Job Control Languages: * one for the operating system lineage that begins with DOS/360 and whose latest member is z/VSE; and * the other for the lineage from OS/360 to z/OS, the latter now including Job Entry Subsystem 2/3, JES extensions, #Job Entry Control Language, Job ''Entry'' Control Language (JECL). They share some basic syntax rules and a few basic concepts, but are otherwise very different. The VM (operating system), VM operating system does not have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
End-of-file
In computing, end-of-file (EOF) is a condition in a computer operating system where no more data can be read from a data source. The data source is usually called a file or stream. Details In the C standard library, the character-reading functions such as getchar return a value equal to the symbolic value (macro) EOF to indicate that an end-of-file condition has occurred. The actual value of EOF is implementation-dependent and must be negative (it is commonly −1, such as in glibc). Block-reading functions return the number of bytes read, and if this is fewer than asked for, then the end of file was reached or an error occurred (checking of errno or dedicated function, such as ferror is required to determine which). EOF character Input from a terminal never really "ends" (unless the device is disconnected), but it is useful to enter more than one "file" into a terminal, so a key sequence is reserved to indicate end of input. In UNIX, the translation of the keystroke to EOF is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthogonal
In mathematics, orthogonality (mathematics), orthogonality is the generalization of the geometric notion of ''perpendicularity''. Although many authors use the two terms ''perpendicular'' and ''orthogonal'' interchangeably, the term ''perpendicular'' is more specifically used for lines and planes that intersect to form a right angle, whereas ''orthogonal'' is used in generalizations, such as ''orthogonal vectors'' or ''orthogonal curves''. ''Orthogonality'' is also used with various meanings that are often weakly related or not related at all with the mathematical meanings. Etymology The word comes from the Ancient Greek ('), meaning "upright", and ('), meaning "angle". The Ancient Greek (') and Classical Latin ' originally denoted a rectangle. Later, they came to mean a right triangle. In the 12th century, the post-classical Latin word ''orthogonalis'' came to mean a right angle or something related to a right angle. Mathematics Physics Optics In optics, polarization ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
