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Cat (command)
cat is a standard Unix utility that reads files sequentially, writing them to standard output. The name is derived from its function to (con)catenate files (from Latin ''catenare'', "to chain"). It has been ported to a number of operating systems. History cat was part of the early versions of Unix, e.g., Version 1, and replaced pr, a PDP-7 and Multics utility for copying a single file to the screen. It was written by Ken Thompson and Dennis Ritchie. The version of cat bundled in GNU coreutils was written by Torbjorn Granlund and Richard Stallman. The ReactOS version was written by David Welch, Semyon Novikov, and Hermès Bélusca. Over time, alternative utilities such as tac and bat also became available, bringing different new features. Usage The Single Unix Specification defines the operation of cat to read files in the sequence given in its arguments, writing their contents to the standard output in the same sequence. The specification mandates the support of one option fla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ken Thompson
Kenneth Lane Thompson (born February 4, 1943) is an American pioneer of computer science. Thompson worked at Bell Labs for most of his career where he designed and implemented the original Unix operating system. He also invented the B programming language, the direct predecessor to the C programming language, and was one of the creators and early developers of the Plan 9 operating system. Since 2006, Thompson has worked at Google, where he co-developed the Go programming language. Other notable contributions included his work on regular expressions and early computer text editors QED and ed, the definition of the UTF-8 encoding, and his work on computer chess that included the creation of endgame tablebases and the chess machine Belle. He won the Turing Award in 1983 with his long-term colleague Dennis Ritchie. Early life and education Thompson was born in New Orleans, Louisiana. When asked how he learned to program, Thompson stated, "I was always fascinated with logic a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multics
Multics ("Multiplexed Information and Computing Service") is an influential early time-sharing operating system based on the concept of a single-level memory.Dennis M. Ritchie, "The Evolution of the Unix Time-sharing System", Communications of the ACM, Vol. 17, 1984, pp. 365-375. Nathan Gregory writes that Multics "has influenced all modern operating systems since, from microcomputers to mainframes." Initial planning and development for Multics started in 1964, in Cambridge, Massachusetts. Originally it was a cooperative project led by MIT (Project MAC with Fernando Corbató) along with General Electric and Bell Labs. It was developed on the GE 645 computer, which was specially designed for it; the first one was delivered to MIT in January 1967. GE offered their earlier 635 systems with an early timesharing system known as "Mark I" and intended to offer the 645 with Multics as a larger successor. Bell withdrew from the project in 1969 as it became clear it would not deliver a wor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
User Interface
In the industrial design field of human–computer interaction, a user interface (UI) is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine from the human end, while the machine simultaneously feeds back information that aids the operators' decision-making process. Examples of this broad concept of user interfaces include the interactive aspects of computer operating systems, hand tools, heavy machinery operator controls and process controls. The design considerations applicable when creating user interfaces are related to, or involve such disciplines as, ergonomics and psychology. Generally, the goal of user interface design is to produce a user interface that makes it easy, efficient, and enjoyable (user-friendly) to operate a machine in the way which produces the desired result (i.e. maximum usability). This generally means that the operator needs to provide minimal input ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dd (Unix)
dd is a command-line utility for Unix, Plan 9, Inferno, and Unix-like operating systems and beyond, the primary purpose of which is to convert and copy files. On Unix, device drivers for hardware (such as hard disk drives) and special device files (such as /dev/zero and /dev/random) appear in the file system just like normal files; can also read and/or write from/to these files, provided that function is implemented in their respective driver. As a result, can be used for tasks such as backing up the boot sector of a hard drive, and obtaining a fixed amount of random data. The program can also perform conversions on the data as it is copied, including byte order swapping and conversion to and from the ASCII and EBCDIC text encodings. History The name is an allusion to the DD statement found in IBM's Job Control Language (JCL), in which it is an abbreviation for "Data Definition". The command's syntax resembles a JCL statement more than other Unix commands do, so much th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jargon File
The Jargon File is a glossary and usage dictionary of slang used by computer programmers. The original Jargon File was a collection of terms from technical cultures such as the MIT AI Lab, the Stanford AI Lab (SAIL) and others of the old ARPANET AI/ LISP/PDP-10 communities, including Bolt, Beranek and Newman, Carnegie Mellon University, and Worcester Polytechnic Institute. It was published in paperback form in 1983 as ''The Hacker's Dictionary'' (edited by Guy Steele), revised in 1991 as ''The New Hacker's Dictionary'' (ed. Eric S. Raymond; third edition published 1996). The concept of the file began with the Tech Model Railroad Club (TMRC) that came out of early TX-0 and PDP-1 hackers in the 1950s, where the term hacker emerged and the ethic, philosophies and some of the nomenclature emerged. 1975 to 1983 The Jargon File (referred to here as "Jargon-1" or "the File") was made by Raphael Finkel at Stanford in 1975. From that time until the plug was finally pulled on the SAIL ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MPEG Program Stream
Program stream (PS or MPEG-PS) is a container format for multiplexing digital audio, video and more. The PS format is specified in MPEG-1 Part 1 (ISO/IEC 11172-1) and MPEG-2 Part 1, Systems (ISO/IEC standard 13818-1/ITU-T H.222.0). The MPEG-2 Program Stream is analogous and similar to ISO/IEC 11172 Systems layer and it is forward compatible.ISO (2000-12-01ISO/IEC 13818-1 : 2000, Second editionPage X, Retrieved on 2009-07-25 Program streams are used on DVD-Video discs and HD DVD video discs, but with some restrictions and extensions.DVD - MPeg differences Retrieved on 2009-07-24 The filename extensions are VOB and EVO respectively. Coding structure |
Digital Container Format
A container format (informally, sometimes called a wrapper) or metafile is a file format that allows multiple data streams to be embedded into a single file, usually along with metadata for identifying and further detailing those streams. Notable examples of container formats include archive files (such as the ZIP format) and formats used for multimedia playback (such as Matroska, MP4, and AVI). Among the earliest cross-platform container formats were Distinguished Encoding Rules and the 1985 Interchange File Format. Design Although containers may identify how data or metadata is encoded, they do not actually provide instructions about how to decode that data. A program that can open a container must also use an appropriate codec to decode its contents. If the program doesn't have the required algorithm, it can't use the contained data. In these cases, programs usually emit an error message that complains of a missing codec, which users may be able to acquire. Container fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Byte Order Mark
The byte order mark (BOM) is a particular usage of the special Unicode character, , whose appearance as a magic number at the start of a text stream can signal several things to a program reading the text: * The byte order, or endianness, of the text stream in the cases of 16-bit and 32-bit encodings; * The fact that the text stream's encoding is Unicode, to a high level of confidence; * Which Unicode character encoding is used. BOM use is optional. Its presence interferes with the use of UTF-8 by software that does not expect non-ASCII bytes at the start of a file but that could otherwise handle the text stream. Unicode can be encoded in units of 8-bit, 16-bit, or 32-bit integers. For the 16- and 32-bit representations, a computer receiving text from arbitrary sources needs to know which byte order the integers are encoded in. The BOM is encoded in the same scheme as the rest of the document and becomes a Unicode code point if its bytes are swapped. Hence, the process access ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ASCII
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 , which severely limited its scope. All modern computer systems instead use Unicode, which has millions of code points, but the first 128 of these are the same as the ASCII set. The Internet Assigned Numbers Authority (IANA) prefers the name US-ASCII for this character encoding. ASCII is one of the List of IEEE milestones, IEEE milestones. Overview ASCII was developed from telegraph code. Its first commercial use was as a seven-bit teleprinter code promoted by Bell data services. Work on the ASCII standard began in May 1961, with the first meeting of the American Standards Association's (ASA) (now the American Nat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OpenBSD
OpenBSD is a security-focused, free and open-source, Unix-like operating system based on the Berkeley Software Distribution (BSD). Theo de Raadt created OpenBSD in 1995 by forking NetBSD 1.0. According to the website, the OpenBSD project emphasizes "portability, standardization, correctness, proactive security and integrated cryptography." The OpenBSD project maintains portable versions of many subsystems as packages for other operating systems. Because of the project's preferred BSD license, many components are reused in proprietary and corporate-sponsored software projects. The firewall code in Apple's macOS is based on OpenBSD's PF firewall code, Android's Bionic C standard library is based on OpenBSD code, LLVM uses OpenBSD's regular expression library, and Windows 10 uses OpenSSH (OpenBSD Secure Shell) with LibreSSL. The word "open" in the name OpenBSD refers to the availability of the operating system source code on the Internet, although the word "open" in the nam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Syntax
In linguistics, syntax () is the study of how words and morphemes combine to form larger units such as phrases and sentences. Central concerns of syntax include word order, grammatical relations, hierarchical sentence structure ( constituency), agreement, the nature of crosslinguistic variation, and the relationship between form and meaning (semantics). There are numerous approaches to syntax that differ in their central assumptions and goals. Etymology The word ''syntax'' comes from Ancient Greek roots: "coordination", which consists of ''syn'', "together", and ''táxis'', "ordering". Topics The field of syntax contains a number of various topics that a syntactic theory is often designed to handle. The relation between the topics is treated differently in different theories, and some of them may not be considered to be distinct but instead to be derived from one another (i.e. word order can be seen as the result of movement rules derived from grammatical relations). Se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
