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Echo (computing)
In telecommunications, echo is the local display of data, either ''initially'' as it is locally sourced and sent, or ''finally'' as a copy of it is received back from a remote destination. Local echo is where the ''local'' sending equipment displays the outgoing sent data. Remote echo is where the display is a return copy of data as received ''remote''ly. Both are used together in a computed form of error detection to ensure that data received at the remote destination of a telecommunication are the same as data sent from the local source (a/k/a echoplex, echo check, or loop check). When (two) modems communicate in echoplex mode the remote modem echoes whatever it receives from the local modem. Terminological confusion: echo is not duplex A displayed 'echo' is independent of 'duplex' (or any) telecommunications transmission protocol. Probably from technical ignorance, "half-duplex" and "full-duplex" are used as slang for 'local echo' (a/k/a echo on) and 'remote echo', respective ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Command-line Interpreter
A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and providing information to them as to what actions they are to perform. In some cases the invocation is conditional based on conditions established by the user or previous executables. Such access was first provided by computer terminals starting in the mid-1960s. This provided an interactive environment not available with punched cards or other input methods. Today, many users rely upon graphical user interfaces and menu-driven interactions. However, some programming and maintenance tasks may not have a graphical user interface and use a command line. Alternatives to the command-line interface include text-based user interface menus (for example, IBM AIX SMIT), keyboard shortcuts, and various desktop metaphors centered on the pointer (us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C-Kermit
Kermit is a computer file transfer/management protocol and a set of communications software tools primarily used in the early years of personal computing in the 1980s. It provides a consistent approach to file transfer, terminal emulation, script programming, and character set conversion across many different computer hardware and operating system platforms. Technical The Kermit protocol supports text and binary file transfers on both full-duplex and half-duplex 8-bit and 7-bit serial connections in a system- and medium-independent fashion, and is implemented on hundreds of different computer and operating system platforms. On full-duplex connections, a sliding window protocol is used with selective retransmission which provides excellent performance and error recovery characteristics. On 7-bit connections, locking shifts provide efficient transfer of 8-bit data. When properly implemented, as in the Columbia University Kermit Software collection, its authors claim performance is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Error Detection And Correction
In information theory and coding theory with applications in computer science and telecommunication, error detection and correction (EDAC) or error control are techniques that enable reliable delivery of digital data over unreliable communication channels. Many communication channels are subject to channel noise, and thus errors may be introduced during transmission from the source to a receiver. Error detection techniques allow detecting such errors, while error correction enables reconstruction of the original data in many cases. Definitions ''Error detection'' is the detection of errors caused by noise or other impairments during transmission from the transmitter to the receiver. ''Error correction'' is the detection of errors and reconstruction of the original, error-free data. History In classical antiquity, copyists of the Hebrew Bible were paid for their work according to the number of stichs (lines of verse). As the prose books of the Bible were hardly ever ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tcsh
tcsh ( “tee-see-shell”, “tee-shell”, or as “tee see ess aitch”, tcsh) is a Unix shell based on and backward compatible with the C shell (csh). Shell It is essentially the C shell with programmable command-line completion, command-line editing, and a few other features. Unlike the other common shells, functions cannot be defined in a tcsh script and the user must use aliases instead (as in csh). It is the native root shell for BSD-based systems such as FreeBSD. tcsh added filename and command completion and command line editing concepts borrowed from the TENEX operating system, which is the source of the “t”. Because it only added functionality and did not change what was there, tcsh remained backward compatible with the original C shell. Though it started as a side branch from the original csh source tree that Bill Joy had created, tcsh is now the main branch for ongoing development. tcsh is very stable but new releases continue to appear roughly once a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell Script
A shell script is a computer program designed to be run by a Unix shell, a command-line interpreter. The various dialects of shell scripts are considered to be scripting languages. Typical operations performed by shell scripts include file manipulation, program execution, and printing text. A script which sets up the environment, runs the program, and does any necessary cleanup or logging, is called a wrapper. The term is also used more generally to mean the automated mode of running an operating system shell; each operating system uses a particular name for these functions including batch files (MSDos-Win95 stream, OS/2), command procedures (VMS), and shell scripts (Windows NT stream and third-party derivatives like 4NT—article is at cmd.exe), and mainframe operating systems are associated with a number of terms. Shells commonly present in Unix and Unix-like systems include the Korn shell, the Bourne shell, and GNU Bash. While a Unix operating system may have a diffe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BSD Version 4 Terminal Interface
The Berkeley Software Distribution or Berkeley Standard Distribution (BSD) is a discontinued operating system based on Research Unix, developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berkeley. The term "BSD" commonly refers to its open-source descendants, including FreeBSD, OpenBSD, NetBSD, and DragonFly BSD. BSD was initially called Berkeley Unix because it was based on the source code of the original Unix developed at Bell Labs. In the 1980s, BSD was widely adopted by workstation vendors in the form of proprietary Unix variants such as DEC Ultrix and Sun Microsystems SunOS due to its permissive licensing and familiarity to many technology company founders and engineers. Although these proprietary BSD derivatives were largely superseded in the 1990s by UNIX SVR4 and OSF/1, later releases provided the basis for several open-source operating systems including FreeBSD, OpenBSD, NetBSD, DragonFly BSD, Darwin, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seventh Edition Unix Terminal Interface
The Seventh Edition Unix terminal interface is the generalized abstraction, comprising both an application programming interface for programs and a set of behavioural expectations for users, of a terminal as historically available in Seventh Edition Unix. It has been largely superseded by the POSIX terminal interface. Concepts and overview The terminal interface provided by Seventh Edition Unix and UNIX/32V, and also presented by BSD version 4 as the ''old terminal driver'', was a simple one, largely geared towards teletypewriters as terminals. Input was entered a line at a time, with the terminal driver in the operating system (and not the terminals themselves) providing simple line editing capabilities. A buffer was maintained by the kernel in which editing took place. Applications reading terminal input would receive the contents of the buffer only when the key was pressed on the terminal to end line editing. The key sent from the terminal to the system would erase (" ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
POSIX Terminal Interface
The POSIX terminal interface is the generalized abstraction, comprising both an application programming interface for programs, and a set of behavioural expectations for users of a terminal, as defined by the POSIX standard and the Single Unix Specification. It is a historical development from the terminal interfaces of BSD version 4 and Seventh Edition Unix. General underlying concepts Hardware A multiplicity of I/O devices are regarded as "terminals" in Unix systems. These include: * serial devices connected by a serial port such as printers/teleprinters, teletypewriters, modems supporting ''remote'' terminals via dial-up access, and directly connected ''local'' terminals * display adapter and keyboard hardware directly incorporated into the system unit, taken together to form a local "console", which may be presented to users and to programs as a single CRT terminal or as multiple virtual terminals * software terminal emulators, such as the xterm, Konsole, GNOME Term ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hayes Command Set
The Hayes command set (also known as the AT command set) is a specific command language originally developed by Dennis Hayes for the Hayes Smartmodem 300 baud modem in 1981. The command set consists of a series of short text strings which can be combined to produce commands for operations such as dialing, hanging up, and changing the parameters of the connection. The vast majority of dial-up modems use the Hayes command set in numerous variations. The command set covered only those operations supported by the earliest 300 bit/s modems. When new commands were required to control additional functionality in higher speed modems, a variety of one-off standards emerged from each of the major vendors. These continued to share the basic command structure and syntax, but added any number of new commands using some sort of prefix character – & for Hayes and USR, and \ for Microcom, for instance. Many of these were re-standardized on the Hayes extensions after the introduction of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microsoft Windows 3
Windows 3.0 is the third major release of Microsoft Windows, launched in 1990. It features a new graphical user interface (GUI) where applications are represented as clickable icons, as opposed to the list of file names seen in its predecessors. Later updates would expand the software's capabilities, one of which added multimedia support for sound recording and playback, as well as support for CD-ROMs. Windows 3.0 is the first version of Windows to perform well both critically and commercially. Critics and users considered its GUI to be a challenger to those of Apple Macintosh and Unix. Other praised features were the improved multitasking, customizability, and especially the utilitarian management of computer memory that troubled the users of Windows 3.0's predecessors. Microsoft was criticized by third-party developers for the bundling of its separate software with the operating environment, which they viewed as an anticompetitive practice. Windows 3.0 sold 10 million co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ProComm
Datastorm Technologies, Inc., was a computer software company that existed from 1986 until 1996. Bruce Barkelew and Thomas Smith founded the company to develop and publish ProComm, a general purpose communications program for personal computers. ProComm flourished in the pre-World Wide Web world, when personal computers used modems to connect over telephone lines with other individual computers, online services such as CompuServe, bulletin board systems (BBSs), Telnet and Gopher sites, and the like. Datastorm was the first company to grow from a shareware publisher into a large commercial software publisher. ProComm 2.4.3 for MS-DOS is still available as shareware. History The death of Andrew Fluegelman, creator of PC-Talk, left a gap in the offerings of dial-up communications and terminal emulation software. Bruce Barkelew and Tom Smith, computer science students at the University of Missouri, formed PIL Software Systems in 1985 to develop ProComm. They distributed the program ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
