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Enquiry Character
In computer communications, enquiry is a transmission-control character that requests a response from the receiving station with which a connection has been set up. It represents a signal intended to trigger a response at the receiving end, to see whether it is still present. The response, an answer-back code to the terminal that transmitted the WRU (who are you) signal, may include station identification, the type of equipment in service, and the status of the remote station. Some teleprinters had a "programmable" drum, which could hold a 20- or 22-character message. The message was encoded on the drum by breaking tabs off the drum. This sequence could be transmitted upon receipt of an enquiry signal, if enabled, or by pressing the "Here is" key on the keyboard. The 5-bit ITA2 has an enquiry character, as do the later ASCII and EBCDIC. In the 1960s, Digital Equipment Corporation, DEC routinely disabled the answerback feature on Teletype Model 33 terminals because it inter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Communications
A computer network is a collection of communicating computers and other devices, such as printers and smart phones. In order to communicate, the computers and devices must be connected by wired media like copper cables, optical fibers, or by wireless communication. The devices may be connected in a variety of network topologies. In order to communicate over the network, computers use agreed-on rules, called communication protocols, over whatever medium is used. The computer network can include personal computers, servers, networking hardware, or other specialized or general-purpose hosts. They are identified by network addresses and may have hostnames. Hostnames serve as memorable labels for the nodes and are rarely changed after initial assignment. Network addresses serve for locating and identifying the nodes by communication protocols such as the Internet Protocol. Computer networks may be classified by many criteria, including the transmission medium used to carry sig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Control Character
In computing and telecommunications, a control character or non-printing character (NPC) is a code point in a character encoding, character set that does not represent a written Character (computing), character or symbol. They are used as in-band signaling to cause effects other than the addition of a symbol to the text. All other characters are mainly ''graphic characters'', also known as ''printing characters'' (or ''printable characters''), except perhaps for "space (punctuation), space" characters. In the ASCII standard there are 33 control characters, such as code 7, , which rings a terminal bell. History Prosigns for Morse code, Procedural signs in Morse code are a form of control character. A form of control characters were introduced in the 1870 Baudot code: NUL and DEL. The 1901 Murray code added the carriage return (CR) and line feed (LF), and other versions of the Baudot code included other control characters. The bell character (BEL), which rang a bell to alert op ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ITA2
The Baudot code () is an early character encoding for telegraphy invented by Émile Baudot in the 1870s. It was the predecessor to the International Telegraph Alphabet No. 2 (ITA2), the most common teleprinter code in use before ASCII. Each Character (symbol), character in the alphabet is represented by a series of five bits, sent over a communication channel such as a telegraph wire or a radio signal by asynchronous serial communication. The symbol rate measurement is known as baud, and is derived from the same name. History Baudot code (ITA1) In the below table, Columns I, II, III, IV, and V show the code; the Let. and Fig. columns show the letters and numbers for the Continental and UK versions; and the sort keys present the table in the order: alphabetical, Gray and UK Baudot developed his first multiplexed telegraph in 1872 [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ASCII
ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control characters a total of 128 code points. The set of available punctuation had significant impact on the syntax of computer languages and text markup. ASCII hugely influenced the design of character sets used by modern computers; for example, the first 128 code points of Unicode are the same as ASCII. ASCII encodes each code-point as a value from 0 to 127 storable as a seven-bit integer. Ninety-five code-points are printable, including digits ''0'' to ''9'', lowercase letters ''a'' to ''z'', uppercase letters ''A'' to ''Z'', and commonly used punctuation symbols. For example, the letter is represented as 105 (decimal). Also, ASCII specifies 33 non-printing control codes which originated with ; most of which are now obsolete. The control cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EBCDIC
Extended Binary Coded Decimal Interchange Code (EBCDIC; ) is an eight- bit character encoding used mainly on IBM mainframe and IBM midrange computer operating systems. It descended from the code used with punched cards and the corresponding six-bit binary-coded decimal code used with most of IBM's computer peripherals of the late 1950s and early 1960s. It is supported by various non-IBM platforms, such as Fujitsu-Siemens' BS2000/OSD, OS-IV, MSP, and MSP-EX, the SDS Sigma series, Unisys VS/9, Unisys MCP and ICL VME. History EBCDIC was devised in 1963 and 1964 by IBM and was announced with the release of the IBM System/360 line of mainframe computers. It is an eight-bit character encoding, developed separately from the seven-bit ASCII encoding scheme. It was created to extend the existing Binary-Coded Decimal (BCD) Interchange Code, or BCDIC, which itself was devised as an efficient means of encoding the two ''zone'' and ''number'' punches on punched cards into six ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Equipment Corporation
Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until he was forced to resign in 1992, after the company had gone into precipitous decline. The company produced many different product lines over its history. It is best known for the work in the minicomputer market starting in the early 1960s. The company produced a series of machines known as the Programmed Data Processor, PDP line, with the PDP-8 and PDP-11 being among the most successful minis in history. Their success was only surpassed by another DEC product, the late-1970s VAX "supermini" systems that were designed to replace the PDP-11. Although a number of competitors had successfully competed with Digital through the 1970s, the VAX cemented the company's place as a leading vendor in the computer space. As microcomputers improved in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VT100
The VT100 is a video terminal, introduced in August 1978 by Digital Equipment Corporation (DEC). It was one of the first terminals to support ANSI escape codes for cursor control and other tasks, and added a number of extended codes for special features like controlling the status lights on the keyboard. This led to rapid uptake of the ANSI standard, which became the de facto standard for hardware video terminals and later terminal emulators. The VT100 series, especially the VT102, was extremely successful in the market, and made DEC the leading terminal vendor at the time. The VT100 series was replaced by the VT200 series starting in 1983, which proved equally successful. Ultimately, over six million terminals in the VT series were sold, based largely on the success of the VT100. Description DEC's first video terminal was the VT05 (1970), succeeded by the VT50 (1974), and soon upgraded to the VT52 (1975). The VT52 featured a text display with 80 columns and 24 rows, bidire ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C0 And C1 Control Codes
The C0 and C1 control code or control character sets define control codes for use in text by computer systems that use ASCII and derivatives of ASCII. The codes represent additional information about the text, such as the position of a cursor, an instruction to start a new line, or a message that the text has been received. C0 codes are the range 00 HEX–1FHEX and the default C0 set was originally defined in ISO 646 (ASCII). C1 codes are the range 80HEX–9FHEX and the default C1 set was originally defined in ECMA-48 (harmonized later with ISO 6429). The ISO/IEC 2022 system of specifying control and graphic characters allows other C0 and C1 sets to be available for specialized applications, but they are rarely used. C0 controls ASCII defines 32 control characters, plus the DEL character. This large number of codes was desirable at the time, as multi-byte controls would require implementation of a state machine in the terminal, which was very difficult with contemporary electr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keepalive
A keepalive (KA) is a message sent by one device to another to check that the link between the two is operating, or to prevent the link from being broken. Description Once a TCP connection has been established, that connection is defined to be valid until one side closes it. Once the connection has entered the connected state, it will remain connected indefinitely. But, in reality, the connection will not last indefinitely. Many firewall or NAT systems will close a connection if there has been no activity in some time period. The Keep Alive signal can be used to trick intermediate hosts to not close the connection due to inactivity. It is also possible that one host is no longer listening (e.g. application or system crash). In this case, the connection is closed, but no FIN was ever sent. In this case, a KeepAlive packet can be used to interrogate a connection to check if it is still intact. A keepalive signal is often sent at predefined intervals, and plays an important role o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
