In computing, output padding is the insertion of non-printing characters into the device output stream to allow for a preceding control operation to take effect.
Output padding was necessary on many printing devices, notably Teletype and other mechanical terminals, after the issuance of a carriage return. [1] Without the padding, following characters might print in the middle of the output line.
Output padding was also necessary on many display terminals after cursor positioning, scrolling, and other commands. [2] [3]
Typically the null character was used; the delete character was occasionally used. The number of padding characters depended on the particular device, but also sometimes on the horizontal position of the printing carriage.
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ASCII, abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of technical limitations of computer systems at the time it was invented, ASCII has just 128 code points, of which only 95 are printable characters, which severely limited its scope. Modern computer systems have evolved to use Unicode, which has millions of code points, but the first 128 of these are the same as the ASCII set.
In computing and telecommunication, a control character or non-printing character (NPC) is a code point in a character set that does not represent a written 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, except perhaps for "space" characters. In the ASCII standard there are 33 control characters, such as code 7, BEL, which rings a terminal bell.
A teleprinter is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations.
In computing and telecommunication, an escape character is a character that invokes an alternative interpretation on the following characters in a character sequence. An escape character is a particular case of metacharacters. Generally, the judgement of whether something is an escape character or not depends on the context.
A line printer prints one entire line of text before advancing to another line. Most early line printers were impact printers.
Dot matrix printing, sometimes called impact matrix printing, is a computer printing process in which ink is applied to a surface using a relatively low-resolution dot matrix for layout. Dot matrix printers are a type of impact printer that prints using a fixed number of pins or wires and typically use a print head that moves back and forth or in an up-and-down motion on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper. They were also known as serial dot matrix printers. Unlike typewriters or line printers that use a similar print mechanism, a dot matrix printer can print arbitrary patterns and not just specific characters.
Daisy wheel printing is an impact printing technology invented in 1970 by Andrew Gabor at Diablo Data Systems. It uses interchangeable pre-formed type elements, each with typically 96 glyphs, to generate high-quality output comparable to premium typewriters such as the IBM Selectric, but two to three times faster. Daisy wheel printing was used in electronic typewriters, word processors and computers from 1972. The daisy wheel is so named because of its resemblance to the daisy flower.
In computer programming, Base64 is a group of binary-to-text encoding schemes that transforms binary data into a sequence of printable characters, limited to a set of 64 unique characters. More specifically, the source binary data is taken 6 bits at a time, then this group of 6 bits is mapped to one of 64 unique characters.
A carriage return, sometimes known as a cartridge return and often shortened to CR, <CR> or return, is a control character or mechanism used to reset a device's position to the beginning of a line of text. It is closely associated with the line feed and newline concepts, although it can be considered separately in its own right.
A newline is a control character or sequence of control characters in character encoding specifications such as ASCII, EBCDIC, Unicode, etc. This character, or a sequence of characters, is used to signify the end of a line of text and the start of a new one.
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. The teletype was an example of an early-day hard-copy terminal and predated the use of a computer screen by decades. Starting in the mid-1970s with machines such as the Sphere 1, Sol-20, and Apple I, terminal circuitry 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.
The Friden Flexowriter produced by the Friden Calculating Machine Company, was a teleprinter, a heavy-duty electric typewriter capable of being driven not only by a human typing, but also automatically by several methods, including direct attachment to a computer and by use of paper tape.
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X.3 is an ITU-T standard indicating what functions are to be performed by a Packet Assembler/Disassembler (PAD) when connecting character-mode data terminal equipment (DTE), such as a computer terminal, to a packet switched network such as an X.25 network, and specifying the parameters that control this operation.
Sixel, short for "six pixels", is a bitmap graphics format supported by terminals and printers from DEC. It consists of a pattern six pixels high and one wide, resulting in 64 possible patterns. Each possible pattern is assigned an ASCII character, making the sixels easy to transmit on 7-bit serial links.
Software flow control is a method of flow control used in computer data links, especially RS-232 serial. It uses special codes, transmitted in-band, over the primary communications channel. These codes are generally called XOFF and XON. Thus, "software flow control" is sometimes called "XON/XOFF flow control". This is in contrast to flow control via dedicated out-of-band signals — "hardware flow control" — such as RS-232 RTS/CTS.
The IBM Selectric was a highly successful line of electric typewriters introduced by IBM on 31 July 1961.
The DECwriter series was a family of computer terminals from Digital Equipment Corporation (DEC). They were typically used in a fashion similar to a teletype, with a computer output being printed to paper and the user inputting information on the keyboard. In contrast to teletypes, the DECwriters were based on dot matrix printer technology, one of the first examples of such a system to be introduced. Versions lacking a keyboard were also available for use as computer printers, which eventually became the only models as smart terminals became the main way to interact with mainframes and minicomputers in the 1980s.
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.
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.