. AT&T Corp. the American Telephone and Telegraph Company, is the subsidiary of AT&T that provides voice, video and Internet telecommunications and professional services to businesses and government agencies. During its long history, AT&T was at times the world's largest telephone company, the world's largest cable television operator, a regulated monopoly. At its peak in the 1950s and 1960s, it employed one million people and its revenue was $3 billion annually. In 2005, AT&T was purchased by Baby Bell and former subsidiary SBC Communications for more than $16 billion. SBC changed its name to AT&T Inc. AT&T started with Bell Patent Association, a legal entity established in 1874 to protect the patent rights of Alexander Graham Bell after he invented the telephone system. A verbal agreement, it was formalized in writing in 1875 as Bell Telephone Company. In 1880 the management of American Bell had created; the project was the first of its kind to create a nationwide long-distance network with a commercially viable cost-structure.
The project was formally incorporated in New York State as a separate company named American Telephone and Telegraph Company on March 3, 1885. Starting from New York, its long-distance telephone network reached Chicago, Illinois, in 1892, with its multitudes of local exchanges continuing to stretch further and further yearly creating a continent-wide telephone system. On December 30, 1899, the assets of American Bell were transferred into its subsidiary American Telephone and Telegraph Company. With this assets transfer on the second to last day of the 19th Century, AT&T became the parent of both American Bell and the Bell System. AT&T was involved in the telephone business and, although it was a partner with RCA, was reluctant to see radio grow because such growth might diminish the demand for wired services, it established station WEAF in New York as. AT&T could provide no programming, but anyone who wished to broadcast a message could pay a "toll" to AT&T and air the message publicly; the original studio was the size of a telephone booth.
The idea, did not take hold, because people would pay to broadcast messages only if they were sure that someone was listening. As a result, WEAF began broadcasting entertainment material, drawing amateur talent found among its employees. Opposition to AT&T's expansion into radio and an agreement with the National Broadcasting Company to lease long distance lines for their broadcasts resulted in the sale of the station and its developing network of affiliates to NBC. Throughout most of the 20th century, AT&T held a monopoly on phone service in the United States and Canada through a network of companies called the Bell System. At this time, the company was nicknamed Ma Bell. On April 30, 1907, Theodore Newton Vail became President of AT&T. Vail believed in the superiority of one phone system and AT&T adopted the slogan "One Policy, One System, Universal Service." This would be the company's philosophy for the next 70 years. Under Vail, AT&T began buying up many of the smaller telephone companies including Western Union telegraph.
These actions brought unwanted attention from antitrust regulators. Anxious to avoid action from government antitrust suits, AT&T and the federal government entered into an agreement known as the Kingsbury Commitment. In the Kingsbury Commitment, AT&T and the government reached an agreement that allowed AT&T to continue operating as a monopoly. While AT&T periodically faced scrutiny from regulators, this state of affairs continued until the company's breakup in 1984; the United States Justice Department opened the case United States v. AT&T in 1974; this was prompted by suspicion that AT&T was using monopoly profits from its Western Electric subsidiary to subsidize the cost of its network, a violation of anti-trust law. A settlement to this case was finalized in 1982, leading to the division of the company on January 1, 1984 into seven Regional Bell Operating Companies known as Baby Bells; these companies were: Ameritech, acquired by SBC in 1999, now part of AT&T Inc. Bell Atlantic, which acquired GTE in 2000 BellSouth, acquired by AT&T Inc. in 2006 NYNEX, acquired by Bell Atlantic in 1996, now part of Verizon Communications Pacific Telesis, acquired by SBC in 1997, now part of AT&T Inc.
Southwestern Bell, which acquired AT&T Corp. in 2005 US West, acquired by Qwest in 2000, which in turn was acquired by CenturyLink in 2011Post-breakup, the former parent company's main business was now AT&T Communications, which focused on long distance services, with other non-RBOC activities. On January 31, 2005, the "Baby Bell" company SBC Communications announced its plans to acquire "Ma Bell" AT&T Corp. for $16 billion. SBC announced in October 2005 that it would shed the "SBC" brand and take the AT&T brand along with the "T" NYSE ticker symbol. Merger approval concluded on November 18, 2005. From 1885 to 1910, AT&T was headquartered at 125 Milk Street in Boston. With its expansion it moved to a headquarters on 195 Broadway; the property belonged to Western Union, of which AT&T held a controlling interest until 1913 when AT&T divested its interest as part of the Kingsbury Commitment. Construction of the current building began in 1912. Designe
In computing, kill is a command, used in several popular operating systems to send signals to running processes. In Unix and Unix-like operating systems, kill is a command used to send a signal to a process. By default, the message sent, but kill is something of a misnomer. The kill command is a wrapper around the kill system call, which sends signals to processes or process groups on the system, referenced by their numeric process IDs or process group IDs. kill is always provided as a standalone utility as defined by the POSIX standard. However, most shells have built-in kill commands that may differ from it. There are many different signals that can be sent, although the signals in which users are most interested are SIGTERM and SIGKILL; the default signal sent is SIGTERM. Programs that handle this signal can do useful cleanup operations before quitting. However, many programs do not implement a special handler for this signal, so a default signal handler is called instead. Other times a process that has a special handler has gone awry in a way that prevents it from properly handling the signal.
All signals except for SIGKILL and SIGSTOP can be "intercepted" by the process, meaning that a special function can be called when the program receives those signals. The two exceptions SIGKILL and SIGSTOP are only seen by the host system's kernel, providing reliable ways of controlling the execution of processes. SIGKILL kills the process, SIGSTOP pauses it until a SIGCONT is received. Unix provides security mechanisms to prevent unauthorized users from killing other processes. For a process to send a signal to another, the owner of the signaling process must be the same as the owner of the receiving process or be the superuser; the available signals all have different names, are mapped to certain numbers. It is important to note that the specific mapping between numbers and signals can vary between Unix implementations. SIGTERM is numbered 15 while SIGKILL is numbered 9. A process can be sent a SIGTERM signal in four ways: The process can be sent a SIGKILL signal in three ways: Other useful signals include HUP, TRAP, INT, SEGV and ALRM.
HUP sends the SIGHUP signal. Some daemons, including Apache and Sendmail, re-read configuration files upon receiving SIGHUP, so the kill command may be used for this too. A SIGINT signal can be generated simply by pressing CTRL+C in most Unix shells, it is common for CTRL+Z to be mapped to SIGTSTP, for CTRL+\ to be mapped to SIGQUIT, which can force a program to do a core dump. Killall - on some variations of Unix, such as Solaris, this utility is automatically invoked when the system is going through a shutdown, it behaves much like the kill command above, but instead of sending a signal to an individual process, the signal is sent to all processes on the system. However, on others such as IRIX, FreeBSD, an argument is supplied specifying the name of the process to kill. For instance, to kill a process such as an instance of the XMMS music player invoked by xmms, the user would run the command killall xmms; this would kill all processes named xmms, is equivalent to kill `pidof xmms` on systems like Solaris.
Pkill - signals processes based on name and other attributes. It was introduced in Solaris 7 and has since been reimplemented for Linux, NetBSD and OpenBSD. Pkill makes killing processes based on their name much more convenient: e.g. to kill a process named firefox without pkill, one would have to type kill `ps --no-headers -C firefox -o pid` whereas with pkill, one can type pkill firefox. Xkill - if called without any parameters, the mouse cursor changes from an arrow to an "x" icon, the user can click on a window to force the X server to close the connection with the client owning the window; this causes the process to terminate when it detects that its connection to the X server has been closed. The kill command is available as a shell builtin in the OS-9 shell, it is used to kill another process by process ID. Stop the process with the process ID "7": In Microsoft's command-line interpreter Windows PowerShell, kill is a predefined command alias for the Stop-Process cmdlet. Microsoft Windows XP, Vista and 7 include the command taskkill to terminate processes.
The usual syntax for this command is taskkill /im "IMAGENAME". An "unsupported" version of kill was included in several releases of the Microsoft Windows Resource Kits available for Windows 98. GNU versions of kill have been ported via Cygwin and run inside of the Unix environment subsystem that Microsoft Windows Services for UNIX provides. Find all processes beginning with the letter "p" that were developed by Microsoft and use more than 10 MB of memory and kill them: Here is a simpler example, which asks the process Explorer.exe to terminate: This example forces the process to terminate: Processes can be killed by their PID number: Singularity shell, the standard shell for Microsoft Research's microkernel operating system Singularity includes a kill command to terminate background processes. Stop the process with the name "SampleProcess": Stop the process with the process identifier "42": Under Plan 9 from Bell Labs, the kill program does not perform this termination, nor does it take process IDs.
Rather, it takes the actual names of processes an
In computing, booting is starting up a computer or computer appliance until it can be used. It can be initiated by software command. After the power is switched on, the computer is dumb and can read only part of its storage called read-only memory. There, a small program is stored called firmware, it does power-on self-tests and, most allows accessing other types of memory like a hard disk and main memory. The firmware runs it. In general purpose computers, but additionally in smartphones and tablets, optionally a boot manager is run; the boot manager lets a user choose which operating system to run and set more complex parameters for it. The firmware or the boot manager loads the boot loader into the memory and runs it; this piece of software is able to place an operating system kernel like Windows or Linux into the computer's main memory and run it. Afterwards, the kernel runs so-called user space software – well known is the graphical user interface, which lets the user log in to the computer or run some other applications.
The whole process may take seconds to tenths of seconds on modern day general purpose computers. Restarting a computer is called reboot, which can be "hard", e.g. after electrical power to the CPU is switched from off to on, or "soft", where the power is not cut. On some systems, a soft boot may optionally clear RAM to zero. Both hard and soft booting can be initiated by hardware such as a button press or by software command. Booting is complete when the operative runtime system operating system and some applications, is attained; the process of returning a computer from a state of hibernation or sleep does not involve booting. Minimally, some embedded systems do not require a noticeable boot sequence to begin functioning and when turned on may run operational programs that are stored in ROM. All computing systems are state machines, a reboot may be the only method to return to a designated zero-state from an unintended, locked state. In addition to loading an operating system or stand-alone utility, the boot process can load a storage dump program for diagnosing problems in an operating system.
Boot is short for bootstrap or bootstrap load and derives from the phrase to pull oneself up by one's bootstraps. The usage calls attention to the requirement that, if most software is loaded onto a computer by other software running on the computer, some mechanism must exist to load the initial software onto the computer. Early computers used a variety of ad-hoc methods to get a small program into memory to solve this problem; the invention of read-only memory of various types solved this paradox by allowing computers to be shipped with a start up program that could not be erased. Growth in the capacity of ROM has allowed more elaborate start up procedures to be implemented. There are many different methods available to load a short initial program into a computer; these methods reach from simple, physical input to removable media that can hold more complex programs. Early computers in the 1940s and 1950s were one-of-a-kind engineering efforts that could take weeks to program and program loading was one of many problems that had to be solved.
An early computer, ENIAC, had no "program" stored in memory, but was set up for each problem by a configuration of interconnecting cables. Bootstrapping did not apply to ENIAC, whose hardware configuration was ready for solving problems as soon as power was applied; the EDSAC system, the second stored program computer to be built, used stepping switches to transfer a fixed program into memory when its start button was pressed. The program stored on this device, which David Wheeler completed in late 1948, loaded further instructions from punched tape and executed them; the first programmable computers for commercial sale, such as the UNIVAC I and the IBM 701 included features to make their operation simpler. They included instructions that performed a complete input or output operation; the same hardware logic could be used to load the contents of a punch card or other input media, such as a magnetic drum or magnetic tape, that contained a bootstrap program by pressing a single button. This booting concept was called a variety of names for IBM computers of the 1950s and early 1960s, but IBM used the term "Initial Program Load" with the IBM 7030 Stretch and used it for their mainframe lines, starting with the System/360 in 1964.
The IBM 701 computer had a "Load" button that initiated reading of the first 36-bit word into main memory from a punched card in a card reader, a magnetic tape in a tape drive, or a magnetic drum unit, depending on the position of the Load Selector switch. The left 18-bit half-word was executed as an instruction, which read additional words into memory; the loaded boot program was executed, which, in turn, loaded a larger program from that medium into memory without further help from the human operator. The term "boot" has been used in this sense since at least 1958. Other IBM computers of that era had similar features. For example, the IBM 1401 system used a card reader to load a program from a punched card; the 80 characters stored in the punched card were read into memory locations 001 to 080 the computer would branch to memory location 001 to read its first stored instruction. This instruction was always the same: move the information in these first 80 memory locations to an assembly area where the information in punched cards 2, 3, 4, so on, could be combined to form the stored program.
Once this information was moved to the assembly area, the machine would branch to an instruction in location 080 and the next card
MacOS is a series of graphical operating systems developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac family of computers. Within the market of desktop and home computers, by web usage, it is the second most used desktop OS, after Microsoft Windows.macOS is the second major series of Macintosh operating systems. The first is colloquially called the "classic" Mac OS, introduced in 1984, the final release of, Mac OS 9 in 1999; the first desktop version, Mac OS X 10.0, was released in March 2001, with its first update, 10.1, arriving that year. After this, Apple began naming its releases after big cats, which lasted until OS X 10.8 Mountain Lion. Since OS X 10.9 Mavericks, releases have been named after locations in California. Apple shortened the name to "OS X" in 2012 and changed it to "macOS" in 2016, adopting the nomenclature that they were using for their other operating systems, iOS, watchOS, tvOS; the latest version is macOS Mojave, publicly released in September 2018.
Between 1999 and 2009, Apple sold. The initial version, Mac OS X Server 1.0, was released in 1999 with a user interface similar to Mac OS 8.5. After this, new versions were introduced concurrently with the desktop version of Mac OS X. Beginning with Mac OS X 10.7 Lion, the server functions were made available as a separate package on the Mac App Store.macOS is based on technologies developed between 1985 and 1997 at NeXT, a company that Apple co-founder Steve Jobs created after leaving the company. The "X" in Mac OS X and OS X is pronounced as such; the X was a prominent part of the operating system's brand identity and marketing in its early years, but receded in prominence since the release of Snow Leopard in 2009. UNIX 03 certification was achieved for the Intel version of Mac OS X 10.5 Leopard and all releases from Mac OS X 10.6 Snow Leopard up to the current version have UNIX 03 certification. MacOS shares its Unix-based core, named Darwin, many of its frameworks with iOS, tvOS and watchOS.
A modified version of Mac OS X 10.4 Tiger was used for the first-generation Apple TV. Releases of Mac OS X from 1999 to 2005 ran on the PowerPC-based Macs of that period. After Apple announced that they were switching to Intel CPUs from 2006 onwards, versions were released for 32-bit and 64-bit Intel-based Macs. Versions from Mac OS X 10.7 Lion run on 64-bit Intel CPUs, in contrast to the ARM architecture used on iOS and watchOS devices, do not support PowerPC applications. The heritage of what would become macOS had originated at NeXT, a company founded by Steve Jobs following his departure from Apple in 1985. There, the Unix-like NeXTSTEP operating system was developed, launched in 1989; the kernel of NeXTSTEP is based upon the Mach kernel, developed at Carnegie Mellon University, with additional kernel layers and low-level user space code derived from parts of BSD. Its graphical user interface was built on top of an object-oriented GUI toolkit using the Objective-C programming language. Throughout the early 1990s, Apple had tried to create a "next-generation" OS to succeed its classic Mac OS through the Taligent and Gershwin projects, but all of them were abandoned.
This led Apple to purchase NeXT in 1996, allowing NeXTSTEP called OPENSTEP, to serve as the basis for Apple's next generation operating system. This purchase led to Steve Jobs returning to Apple as an interim, the permanent CEO, shepherding the transformation of the programmer-friendly OPENSTEP into a system that would be adopted by Apple's primary market of home users and creative professionals; the project was first code named "Rhapsody" and officially named Mac OS X. Mac OS X was presented as the tenth major version of Apple's operating system for Macintosh computers. Previous Macintosh operating systems were named using Arabic numerals, as with Mac OS 8 and Mac OS 9; the letter "X" in Mac OS X's name refers to a Roman numeral. It is therefore pronounced "ten" in this context. However, it is commonly pronounced like the letter "X"; the first version of Mac OS X, Mac OS X Server 1.0, was a transitional product, featuring an interface resembling the classic Mac OS, though it was not compatible with software designed for the older system.
Consumer releases of Mac OS X included more backward compatibility. Mac OS applications could be rewritten to run natively via the Carbon API; the consumer version of Mac OS X was launched in 2001 with Mac OS X 10.0. Reviews were variable, with extensive praise for its sophisticated, glossy Aqua interface but criticizing it for sluggish performance. With Apple's popularity at a low, the makers of several classic Mac applications such as FrameMaker and PageMaker declined to develop new versions of their software for Mac OS X. Ars Technica columnist John Siracusa, who reviewed every major OS X release up to 10.10, described the early releases in retrospect as'dog-slow, feature poor' and Aqua as'unbearably slow and a huge resource hog'. Apple developed several new releases of Mac OS X. Siracusa's review of version 10.3, noted "It's strange to have gone from years of uncertainty and vaporware to a steady annual supply of major new operating system releases." Version 10.4, Tiger shocked executives at Microsoft by offering a number of features, such as fast file s
OS X Mountain Lion
OS X Mountain Lion is the ninth major release of OS X, Apple Inc.'s desktop and server operating system for Macintosh computers. OS X Mountain Lion was released on July 25, 2012 for purchase and download through Apple's Mac App Store, as part of a switch to releasing OS X versions online and every year, rather than every two years or so. Named to signify its status as a refinement of the previous Mac OS X version, Apple's stated aims in developing Mountain Lion were to allow users to more manage and synchronise content between multiple Apple devices and to make the operating system more familiar; the operating system gained the new malware-blocking system Gatekeeper and integration with Apple's online Game Center and iCloud services, while the Safari web browser was updated to version 6. As on iOS, Notes and Reminders became full applications, separate from Mail and Calendar, while the iChat application was replaced with a version of iOS's Messages. Mountain Lion added a version of iOS's Notification Center, which groups updates from different applications in one place.
Integrated links allowing the user to transfer content to Twitter were present in the operating system from launch. Facebook integration was planned but unfinished at launch date, it was released as a downloadable update later. OS X Mountain Lion received positive reviews, with critics praising Notification Center and speed improvements over Mac OS X Lion, while criticizing iCloud for unreliability and Game Center for lack of games. Mountain Lion sold three million units in the first four days, has sold 28 million units as of June 10, 2013, making it Apple's most popular OS X release. Mountain Lion was the last paid upgrade for an OS X major release, with OS X Mavericks and being free. OS X Mountain Lion was announced by Apple on their website on February 16, 2012, as a successor to Mac OS X 10.7 Lion. It achieved golden master status on July 9, 2012. Following a soft transition started with Mac OS X Lion, Apple refers to OS X Mountain Lion as "OS X" rather than "Mac OS X". During the Apple Worldwide Developers Conference keynote on June 11, 2012, Apple announced a "near final" release version of Mountain Lion for developers, with the public version arriving in July 2012 at a price tag of US$19.99.
The third generation MacBook Pro, revised MacBook Air, iPad Smart Case, third-generation AirPort Express were announced at the keynote as well. The specific release date of July 25 was not confirmed until the day before, July 24, by Apple CEO, Tim Cook, as part of Apple's 2012 third-quarter earnings announcement, it was released to the Mac App Store on July 25, 2012, where it sold 3 million units in the first four days of release. An update for Mountain Lion, version 10.8.1, was released on August 23, 2012. It resolved issues with iMessages, Migration Assistant, Microsoft Exchange Server and many other applications. Tests of the update revealed that 10.8.1 improved battery life on laptops, albeit gaining back only half of the battery life, lost in updating to Mountain Lion. Although 10.8.1 improved battery life for some customers, others continue to complain about reduced battery life and a constant drop in battery health resulting in a "Service Battery" message. The official system requirements of OS X 10.8 are 2 GB RAM, 8 GB available storage, OS X 10.6.8 or on any of the following Macs: iMac MacBook, MacBook Pro MacBook Air Mac Mini Mac Pro Xserve As in 10.7, the earliest models supporting AirDrop are the late-2008 MacBook Pro, late-2010 MacBook Air, late-2008 MacBook, mid-2010 Mac Mini, early-2009 Mac Pro with an AirPort Extreme card.
Any Mac released in or after 2011, except the MacBook, supports AirPlay Mirroring. Power Nap is supported on the MacBook Pro with Retina display; the technical basis for these requirements is incompatibility with 32-bit EFI and 32-bit kernel extensions. In order to prevent incompatible systems from installing 10.8, the installer contains a whitelist of supported motherboard IDs. Users have bypassed these limitations so that 10.8 may run with varying functionality on some unsupported computers. Notification Center was added in the operating system, it provides an overview of alerts from applications and displays notifications until the user completes an associated action, rather than requiring instant resolution. Users may choose what applications appear in Notification Center, how they are handled. There are three types of notifications: banners and badges. Banners are displayed for a short period of time in the upper right corner of the Mac's screen, slide off to the right; the icon of the application is displayed on the left side of the banner, while the message from the application will be displayed on the right side.
Alerts will not disappear from the screen until the user takes action. Badges are red notification icons, they indicate the number of items available for the application. Notification Center can be accessed by clicking the icon in the right corner of the menu bar; when open, the user can click a button to tweet, post status updates to Facebook, or view all notifications in the sidebar pane. Swiping up will reveal the option to disable Notification Center for on
An error message is information displayed when an unexpected condition occurs on a computer or other device. On modern operating systems with graphical user interfaces, error messages are displayed using dialog boxes. Error messages are used when user intervention is required, to indicate that a desired operation has failed, or to relay important warnings. Error messages are seen throughout computing, are part of every operating system or computer hardware device. Proper design of error messages is an important topic in usability and other fields of human–computer interaction; the following error messages are seen by modern computer users: Access denied This error occurs if the user has insufficient privileges to a file, or if it has been locked by some program or user. Device not ready This error most occurs when there is no floppy disk in the disk drive and the system tries to perform tasks involving this disk. File not found The file concerned may have been damaged, deleted, or a bug may have caused the error.
Alternatively, the file might not exist, or the user has mistyped its name. More frequent on command line interfaces than on graphical user interfaces where files are presented iconically and users do not type file names. Low Disk Space This error occurs. To fix this, the user should delete some files, or get a bigger hard drive. Out of memory This error occurs when the system has run out of memory or tries to load a file too large to store in RAM; the fix is to install more memory. Has needs to close. We are sorry for the inconvenience; this message is displayed by Microsoft Windows XP when a program causes a general protection fault or invalid page fault. In Windows 7 it is changed into a more simple " has stopped working". Abort, Fail? - A notoriously confusing error message seen in MS-DOS Bad command or file name - Another notoriously common and confusing error message seen in MS-DOS The Blue Screen of Death - On Microsoft Windows and ReactOS operating systems, this screen appears when Windows or ReactOS can no longer run because of a severe error.
It is analogous to a kernel panic on Linux, Unix or Mac OS X. Can't extend - an error message from Acorn DFS. DFS stores files in non-fragmented contiguous disk space, this error is caused when trying to extend an open random-access file into space, occupied by another file. Guru Meditation - an error message from the Commodore Amiga analogous to a kernel panic or Blue Screen of Death adopted by more recent products such as VirtualBox HTTP 404 - A file not found error seen on the World Wide Web resulting from a link to a page, moved or deleted, or a mistyped URL lp0 on fire - A Unix warning that the printer may be on fire Not a typewriter - A Unix error message, confusing due to its now obsolete use of the word typewriter, and, sometimes output when the nature of error is different PC LOAD LETTER - An error on several HP laser printers that asked the user to add "Letter" size paper in a confusing way SYNTAX ERROR - Seen on many computer systems when the received instructions are in a format they don't understand HTTP 504 - An error found on the World Wide Web stating that a gateway timeout occurred in the internet link.
Error 1603 - An error that states that a problem during installation of a computer program, this error occurs on Windows computer systems. <application name> has stopped - An error message found on Android devices, which states a current running application unexpectedly stops working or crashes. Success - one of the error messages that occurs when the program has detected an error condition, yet the actual error message printing routine relies on C library to print the error reported by the operating system, while the underlying system calls have succeeded and report no errors; this is a form of sloppy error handling, confusing for the users. With the rise of Web 2.0 services such as Twitter, end-user facing error messages such as HTTP 404 and HTTP 500 started to be displayed with whimsical characters, termed Fail Pets or Error Mascots. The term "Fail Pet" was coined, or at least first used in print, by Mozilla Engineer Fred Wenzel in a post on his blog entitled "Why Wikipedia might need a fail-pet — and why Mozilla does not."
Dr. Sean Rintel argues that error messages are a critical strategic moment in brand awareness and loyalty. Fail pets are of interest to marketers. "However, that same recognition carries the danger of highlighting service failure." The most famous fail pet is Twitter's Fail Whale. Other fail pets include: Ars Technica: Moon Shark FarmVille on Facebook: Sad cow. GitHub: Octocat Google: Broken robot iCloud: Cloud with Apple System 7 emoticon-style face Macintosh: Sad Mac Tumblr: Tumbeasts Twitter: Fail Whale / Twitter Robot YouTube: Televisions, light static inside video window Cartoon Network: BMO: Domo Google Chrome: T-Rex The form that error messages take varies between operating systems and programs. Error messages on hardware devices, like computer peripherals, may take the form of dedicated lights indicating an error condition, a brief code that needs to be interpreted using a look-up sheet or a manual, or via a more detailed message on a display
In computing, rebooting is the process by which a running computer system is restarted, either intentionally or unintentionally. Reboots can be either "cold" where the power to the system is physically turned off and back on again, causing an initial boot of the machine, or warm where the system restarts without the need to interrupt the power; the term restart is used to refer to a reboot when the operating system closes all programs and finalizes all pending input and output operations before initiating a soft reboot. Early electronic computers had no operating system and little internal memory; the input was a stack of punch cards. The computer was initiated by pressing a start button that performed a single command, read a card; this first card instructed the machine to read more cards that loaded a user program. This process was likened to an old saying, "picking yourself up by the bootstraps", referring to a horseman who lifts himself off the ground by pulling on the straps of his boots.
This set of initiating punch cards was called "bootstrap cards". Thus a cold start was called booting the computer up. If the computer crashed, it was rebooted; the boot reference carried over to all subsequent types of computers. For more, see Bootstrapping. Technical sources describe two contrasting forms of reboot known as a cold reboot and warm reboot, although the definition of these forms can vary between sources. According to Jones and Tittel, Cooper and Soper, on IBM PC compatible platform, a cold boot is a boot process in which the computer starts from a powerless state. All except Tulloch mention that in cold boot, the system performs a power-on self-test. In addition to the power switch and Soper state that the reset button, if present, may commence a cold reboot. Jones and Tittel contradicts this assertion and states that a reset button may commence either a cold or warm reboot, depending on the system. Microsoft Support article 102228 confers that although the reset button is designed to perform a cold reboot, it may not disconnect the power to the motherboard – a state that does not correspond to the cold boot definition given above.
According to Jones and Tittel, both the operating system and third-party software can initiate a cold boot. Finding a definition for warm boot, however, is more of a challenge. All aforementioned sources indicate that a warm boot is initiated by pressing Ctrl + Alt + Delete key combination. Jones and Tittel specifies that for a warm reboot to occur, BIOS must be the recipient of the key combination. Microsoft Support article 102228 takes a more technical approach and defines warm boot as the result of invoking INT 19h, a BIOS interrupt call, with the Ctrl + Alt + Delete key combination being only one way of achieving this. According to Grimes, malware may prevent or subvert a warm boot by intercepting the Ctrl + Alt + Delete key combination and prevent it from reaching BIOS; the Windows NT family of operating systems does the same and reserves the key combination for its own use. Soper asserts that the Windows "Restart" command initiates a warm boot, thus contradicting Jones and Tittel, who believe the same action performs a cold boot.
The Linux family of operating systems supports an alternative to warm boot. The entire process occurs independently of the system firmware; the kernel being executed does not have to be a Linux kernel. Outside the domain of IBM compatible PCs, the types of boot may not be as disambiguous. According to Sue Loh of Windows CE Base Team, Windows CE devices support three types of boots: Warm and clean. A warm boot discards program memory. A cold boot additionally discards storage memory, while a clean boot erases all forms of memory storage from the device. However, since these areas do not exist on all Windows CE devices, users are only concerned with two forms of reboot: one that resets the volatile memory and one that wipes the device clean and restores factory settings. For example, for a Windows Mobile 5.0 device, the former is a cold boot and the latter is a clean boot. A hard reboot means that the system is not shut down in an orderly manner, skipping file system synchronisation and other activities that would occur on an orderly shutdown.
This can be achieved by either applying a reset, by cycling power, by issuing the halt -q command in most Unix-like systems, or by triggering a kernel panic. The term "restart" is used by Microsoft Windows and Linux family of operating systems to denote an operating system-assisted reboot. In a restart, the operating system ensures that all pending I/O operations are gracefully ended before commencing a reboot. Users may deliberately initiate a reboot. Rationale for such action may include: Troubleshooting: Rebooting may be used by users, support staff or system administrators as a technique to work around bugs in software, for example memory leaks or processes that hog resources to the detriment of the overall system, or to terminate malware. While this approach does not address the root cause of the issue, resetting a system back to a good, known state may allow it to be used again for some period until the issue next occurs. Switching operating systems: On a multi-boot system