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Flag Day (computing)
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 requir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
System Administration
A system administrator, or 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 administrator (DBA) maintains a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backward Compatibility
Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially in telecommunications and computing. Modifying a system in a way that does not allow backward compatibility is sometimes called " breaking" backward compatibility. A complementary concept is forward compatibility. A design that is forward-compatible usually has a roadmap for compatibility with future standards and products. A related term from programming jargon is hysterical reasons or hysterical raisins (near-homophones for "historical reasons"), as the purpose of some software features may be solely to support older hardware or software versions. Usage In hardware A simple example of both backward and forward compatibility is the introduction of FM radio in stereo. FM radio was initially mono, with only one audio channel represented ... [...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 compatibility is no ... [...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'', ''machine'', and ''table'' are pronounced according to English rules of phonology, rather than French, and are commonly used by English speakers without any consciousness of their French origin. This article, on the other hand, 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 diacritics and are usually printed in italics. In spoken English, at least some attempt is generally made to pronounce them as they would sound in French; an entirely English pronunciation is reg ... [...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] |
Operating System
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, 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 computer from cellular phones and video game consoles to web servers and supercomputers. The dominant general-purpose personal computer operating system is Microsoft Windows with a market share of around 74.99%. macOS by Apple Inc. is in second place (14.84%), and ... [...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] |
Flag Day (United States)
In the United States, Flag Day is celebrated on June 14. It commemorates the adoption of the flag of the United States on June 14, 1777, by Flag Acts (United States), resolution of the Continental Congress, Second Continental Congress. The Flag Resolution, passed on June 14, 1777, stated: "Resolved, 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." The United States Army also celebrates the U.S. Army Birthdays, U.S. Army birthday on this date; Congress adopted "the American continental army" after reaching a consensus position in the Committee of the Whole on June 14, 1775. In 1916, President Woodrow Wilson issued a proclamation that officially established June 14 as Flag Day; on August 3, 1949, National Flag Day was established by an Act of Congress. Flag Day is not an official Federal holidays in the United States, federal holiday. Title 36 of t ... [...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 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 (ARPA) of the United States Department of Defense. Building on the ideas of J. C. R. Licklider, Bob Taylor initiated the ARPANET project in 1966 to enable access to remote computers. Taylor appointed Larry Roberts as program manager. Roberts made the key decisions about the network design. He incorporated Donald Davies' concepts and designs for packet switching, and sought input from Paul Baran. ARPA awarded the contract to build the network to Bolt Beranek & Newman who developed the first protocol for the network. Roberts engaged Leonard Kleinrock at UCLA to develop mathematical methods for analyzing the packet network technology. The first ... [...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 middle layers 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 addresses, 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 for each application down 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 a ... [...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 set of 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). In the development of this networking model, early versions of it 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 high ... [...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 standards. He is known principally for being the Editor of the 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 as his M.S. (1968) in Engineering. He t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
