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Flag Day (software)
A flag day, as used in system administration, is a change which requires a complete restart or conversion of a sizable body of software or data. The change is large and expensive, and—in the event of failure—similarly difficult and expensive to reverse. The situation may arise if there are limitations on backward compatibility and forward compatibility among system components, which then requires that updates be performed almost simultaneously (during a "flag day cutover") for the system to function after the upgrade. This contrasts with the method of gradually phased-in upgrades, which avoids the disruption of service caused by ''en masse'' upgrades. This systems terminology originates from a major change in the Multics operating system's definition of ASCII, which was scheduled for the United States holiday, Flag Day, on June 14, 1966. Another historical flag day was January 1, 1983, when the ARPANET changed from NCP to the TCP/IP protocol suite. This major change required ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
System Administration
An IT administrator, system administrator, sysadmin, or admin is a person who is responsible for the upkeep, configuration, and reliable operation of computer systems, especially multi-user computers, such as servers. The system administrator seeks to ensure that the uptime, performance, resources, and security of the computers they manage meet the needs of the users, without exceeding a set budget when doing so. To meet these needs, a system administrator may acquire, install, or upgrade computer components and software; provide routine automation; maintain security policies; troubleshoot; train or supervise staff; or offer technical support for projects. Related fields Many organizations staff offer jobs related to system administration. In a larger company, these may all be separate positions within a computer support or Information Services (IS) department. In a smaller group they may be shared by a few sysadmins, or even a single person. * A database administ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backward Compatibility
In telecommunications and computing, backward compatibility (or backwards compatibility) is a property of an operating system, software, real-world product, or technology that allows for interoperability with an older legacy system, or with Input/output, input designed for such a system. Modifying a system in a way that does not allow backward compatibility is sometimes called "wikt:breaking change, breaking" backward compatibility. Such breaking usually incurs various types of costs, such as Switching barriers, switching cost. A complementary concept is ''forward compatibility''; a design that is forward-compatible usually has a Technology roadmap, roadmap for compatibility with future standards and products. Usage In hardware A simple example of both backward and forward compatibility is the introduction of FM broadcasting, FM radio in stereophonic sound, stereo. FM radio was initially monaural, mono, with only one audio channel represented by one signal (electrical engineerin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forward Compatibility
Forward compatibility or upward compatibility is a design characteristic that allows a system to accept input intended for a later version of itself. The concept can be applied to entire systems, electrical interfaces, telecommunication signals, data communication protocols, file formats, and programming languages. A standard supports forward compatibility if a product that complies with earlier versions can " gracefully" process input designed for later versions of the standard, ignoring new parts which it does not understand. The objective for forward compatible technology is for old devices to recognise when data has been generated for new devices. Forward compatibility for the older system usually means backward compatibility for the new system, i.e. the ability to process data from the old system; the new system usually has ''full'' compatibility with the older one, by being able to both process and generate data in the format of the older system. Forward compatibilit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
En Masse
Many words in the English vocabulary are of French origin, most coming from the Anglo-Norman spoken by the upper classes in England for several hundred years after the Norman Conquest, before the language settled into what became Modern English. English words of French origin, such as ''art'', ''competition'', ''force'', ''money'', and ''table'' are pronounced according to English rules of phonology, rather than French, and English speakers commonly use them without any awareness of their French origin. This article covers French words and phrases that have entered the English lexicon without ever losing their character as Gallicisms: they remain unmistakably "French" to an English speaker. They are most common in written English, where they retain French diacritic A diacritic (also diacritical mark, diacritical point, diacritical sign, or accent) is a glyph added to a letter or to a basic glyph. The term derives from the Ancient Greek (, "distinguishing"), from (, ... [...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. It has been written 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 the Dartmouth Time-Sharing System which they called "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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating System
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for efficient use of the system and may also include accounting software for cost allocation of Scheduling (computing), processor time, mass storage, peripherals, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computerfrom cellular phones and video game consoles to web servers and supercomputers. , Android (operating system), Android is the most popular operating system with a 46% market share, followed ... [...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] |
Flag Day (United States)
Flag Day is a holiday celebrated on June 14 in the United States. It commemorates the adoption of the flag of the United States on June 14, 1777, by resolution of the Second Continental Congress. The Flag Resolution stated "That the flag of the thirteen United States be thirteen stripes, alternate red and white; that the union be thirteen stars, white in a blue field, representing a new constellation." Flag Day was first proposed in 1861 to rally support for the Union side of the American Civil War. In 1916, President Woodrow Wilson issued a Presidential proclamation (United States), presidential proclamation that designated June 14 as Flag Day. On August 3, 1949, National Flag Day was officially established by an Act of Congress. On June 14, 1937, Pennsylvania became the first state to celebrate Flag Day as a state holiday, beginning in the town of Rennerdale. New York Consolidated Laws designate the second Sunday in June as Flag Day, a state holiday. Flag Day is not an offici ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ARPANET
The Advanced Research Projects Agency Network (ARPANET) was the first wide-area packet-switched network with distributed control and one of the first computer networks to implement the TCP/IP protocol suite. Both technologies became the technical foundation of the Internet. The ARPANET was established by the Advanced Research Projects Agency (now DARPA) of the United States Department of Defense. Building on the ideas of J. C. R. Licklider, Robert Taylor (computer scientist), Bob Taylor initiated the ARPANET project in 1966 to enable resource sharing between remote computers. Taylor appointed Lawrence Roberts (scientist), Larry Roberts as program manager. Roberts made the key decisions about the request for proposal to build the network. He incorporated Donald Davies' concepts and designs for packet switching, and sought input from Paul Baran on dynamic routing. In 1969, ARPA awarded the contract to build the Interface Message Processors (IMPs) for the network to Bolt Berane ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Control Protocol (ARPANET)
The Network Control Protocol (NCP) was a communication protocol for a computer network in the 1970s and early 1980s. It provided the transport layer of the protocol stack running on host computers of the ARPANET, the predecessor to the modern Internet. NCP preceded the Transmission Control Protocol (TCP) as a transport layer protocol used during the early ARPANET. NCP was a simplex protocol that utilized two port numbers, establishing two connections for two-way communications. An odd and an even port were reserved for each application layer application or protocol. The standardization of TCP and UDP reduced the need for the use of two simplex ports per application to one duplex port. There is some confusion over the name, even among the engineers who worked with the ARPANET. Originally, there was no need for a name for the protocol stack as a whole, so none existed. When the development of TCP started, a name was required for its predecessor, and the pre-existing acronym 'NCP' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TCP/IP
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and the Internet Protocol (IP). Early versions of this networking model were known as the Department of Defense (DoD) model because the research and development were funded by the United States Department of Defense through DARPA. The Internet protocol suite provides end-to-end data communication specifying how data should be packetized, addressed, transmitted, routed, and received. This functionality is organized into four abstraction layers, which classify all related protocols according to each protocol's scope of networking. An implementation of the layers for a particular application forms a protocol stack. From lowest to highest, the layers are the li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jon Postel
Jonathan Bruce Postel (; August 6, 1943 – October 16, 1998) was an American computer scientist who made many significant contributions to the development of the Internet, particularly with respect to Internet Standard, standards. He is known principally for being the Editor of the Request for Comments, Request for Comment (RFC) document series, for Simple Mail Transfer Protocol (SMTP), and for administering the Internet Assigned Numbers Authority (IANA) until his death. During his lifetime he was referred to as the "god of the Internet" for his comprehensive influence; Postel himself noted that this "compliment" came with a barb, the suggestion that he should be replaced by a "professional," and responded with typical self-effacing matter-of-factness: "Of course, there isn’t any 'God of the Internet.' The Internet works because a lot of people cooperate to do things together." Career Postel attended Van Nuys High School, and then UCLA where he earned his B.S. (1966) as well ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
