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X Window System	History	X.Org and XFree86 XFree86 originated in 1992 from the X386 server for IBM PC compatibles included with X11R5 in 1991, written by Thomas Roell and Mark W. Snitily and donated to the MIT X Consortium by Snitily Graphics Consulting Services (SGCS). XFree86 evolved over time from just one port of X to the leading and most popular implementation and the de facto standard of X's development.In May 1999, The Open Group formed X.Org. X.Org supervised the release of versions X11R6.5.1 onward. X development at this time had become moribund; most technical innovation since the X Consortium had dissolved had taken place in the XFree86 project. In 1999, the XFree86 team joined X.Org as an honorary (non-paying) member, encouraged by various hardware companies interested in using XFree86 with Linux and in its status as the most popular version of X.
X Window System	History	By 2003, while the popularity of Linux (and hence the installed base of X) surged, X.Org remained inactive, and active development took place largely within XFree86. However, considerable dissent developed within XFree86. The XFree86 project suffered from a perception of a far too cathedral-like development model; developers could not get CVS commit access and vendors had to maintain extensive patch sets. In March 2003, the XFree86 organization expelled Keith Packard, who had joined XFree86 after the end of the original MIT X Consortium, with considerable ill feeling.X.Org and XFree86 began discussing a reorganisation suited to properly nurturing the development of X. Jim Gettys had been pushing strongly for an open development model since at least 2000. Gettys, Packard and several others began discussing in detail the requirements for the effective governance of X with open development.
X Window System	History	Finally, in an echo of the X11R6.4 licensing dispute, XFree86 released version 4.4 in February 2004 under a more restrictive license which many projects relying on X found unacceptable. The added clause to the license was based on the original BSD license's advertising clause, which was viewed by the Free Software Foundation and Debian as incompatible with the GNU General Public License. Other groups saw it as against the spirit of the original X. Theo de Raadt of OpenBSD, for instance, threatened to fork XFree86 citing license concerns. The license issue, combined with the difficulties in getting changes in, left many feeling the time was ripe for a fork.
X Window System	History	The X.Org Foundation In early 2004, various people from X.Org and freedesktop.org formed the X.Org Foundation, and the Open Group gave it control of the x.org domain name. This marked a radical change in the governance of X. Whereas the stewards of X since 1988 (including the prior X.Org) had been vendor organizations, the Foundation was led by software developers and used community development based on the bazaar model, which relies on outside involvement. Membership was opened to individuals, with corporate membership being in the form of sponsorship. Several major corporations such as Hewlett-Packard currently support the X.Org Foundation.
X Window System	History	The Foundation takes an oversight role over X development: technical decisions are made on their merits by achieving rough consensus among community members. Technical decisions are not made by the board of directors; in this sense, it is strongly modelled on the technically non-interventionist GNOME Foundation. The Foundation employs no developers.
X Window System	History	The Foundation released X11R6.7, the X.Org Server, in April 2004, based on XFree86 4.4RC2 with X11R6.6 changes merged. Gettys and Packard had taken the last version of XFree86 under the old license and, by making a point of an open development model and retaining GPL compatibility, brought many of the old XFree86 developers on board.While X11 had received extensions such as OpenGL support during the 1990s, its architecture had remained fundamentally unchanged during the decade. In the early part of the 2000s, however, it was overhauled to resolve a number of problems that had surfaced over the years, including a "flawed" font architecture, a 2D graphics system "which had always been intended to be augmented and/or replaced", and latency issues.
X Window System	History	X11R6.8 came out in September 2004. It added significant new features, including preliminary support for translucent windows and other sophisticated visual effects, screen magnifiers and thumbnailers, and facilities to integrate with 3D immersive display systems such as Sun's Project Looking Glass and the Croquet project. External applications called compositing window managers provide policy for the visual appearance.
X Window System	History	On 21 December 2005, X.Org released X11R6.9, the monolithic source tree for legacy users, and X11R7.0, the same source code separated into independent modules, each maintainable in separate projects. The Foundation released X11R7.1 on 22 May 2006, about four months after 7.0, with considerable feature improvements.XFree86 development continued for a few more years, 4.8.0 being released on 15 December 2008.
X Window System	Nomenclature	The proper names for the system are listed in the manual page as X; X Window System; X Version 11; X Window System, Version 11; or X11.The term "X-Windows" (in the manner of the subsequently released "Microsoft Windows") is not officially endorsed – with X Consortium release manager Matt Landau stating in 1993, "There is no such thing as 'X Windows' or 'X Window', despite the repeated misuse of the forms by the trade rags" – though it has been in common informal use since early in the history of X and has been used deliberately for provocative effect, for example in the Unix-Haters Handbook.
X Window System	Nomenclature	Key terms The X Window System has nuanced usage of a number of terms when compared to common usage, particularly "display" and "screen", a subset of which is given here for convenience: device A graphics device such as a computer graphics card or a computer motherboard's integrated graphics chipset. monitor A physical device such as a CRT or a flat screen computer display.
X Window System	Nomenclature	screen An area into which graphics may be rendered, either through software alone into system memory as with VNC, or within a graphics device, some of which can render into more than one screen simultaneously, either viewable simultaneously or interchangeably. Interchangeable screens are often set up to be notionally left and right from one another, flipping from one to the next as the mouse pointer reaches the edge of the monitor.
X Window System	Nomenclature	virtual screen Two different meanings are associated with this term: A technique allowing panning a monitor around a screen running at a larger resolution than the monitor is currently displaying.
X Window System	Nomenclature	An effect simulated by a window manager by maintaining window position information in a larger coordinate system than the screen and allowing panning by simply moving the windows in response to the user.display A collection of screens, often involving multiple monitors, generally configured to allow the mouse to move the pointer to any position within them. Linux-based workstations are usually capable of having multiple displays, among which the user can switch with a special keyboard combination such as control-alt-function-key, simultaneously flipping all the monitors from showing the screens of one display to the screens in another.The term "display" should not be confused with the more specialized jargon "Zaphod display". The latter is a rare configuration allowing multiple users of a single computer to each have an independent set of display, mouse, and keyboard, as though they were using separate computers, but at a lower per-seat cost.
X Window System	Release history	On the prospect of future versions, the X.org website states: X.Org continues to develop and release the X Window System software components. These are released individually as each component is ready, without waiting for a overall X Window System "katamari" release schedule - see the individual X.Org releases directory for downloads, and the xorg-announce archives or git repositories for details on included changes. No release plan for a X11R7.8 rollup katamari release has been proposed.
Mothers against decapentaplegic	Mothers against decapentaplegic	Mothers against decapentaplegic is a protein from the SMAD family that was discovered in Drosophila. During Drosophila research, it was found that a mutation in the gene in the mother repressed the gene decapentaplegic in the embryo. The phrase "Mothers against" was added as a humorous take-off on organizations opposing various issues e.g. Mothers Against Drunk Driving (MADD); and based on a tradition of such unusual naming within the gene research community.Several human homologues are known: Mothers against decapentaplegic homolog 1 Mothers against decapentaplegic homolog 2 Mothers against decapentaplegic homolog 3 Mothers against decapentaplegic homolog 4 Mothers against decapentaplegic homolog 5 Mothers against decapentaplegic homolog 6 Mothers against decapentaplegic homolog 7 Mothers against decapentaplegic homolog 9
Cyberflora	Cyberflora	The Cyberflora project is a project developed by the Media Lab at Massachusetts Institute of Technology. The project is part of the Anima Machina program at MIT - a program that was developed by Assistant Professor of Media Arts and Sciences and Director of the Robotic Life Group Cynthia Breazeal. The Cyberflora project allowed Breazeal and students involved in the media lab to investigate emotional intelligence in a breed of robots that combines both plant and animal characteristics.
Cyberflora	The Garden	Breazeal's mechanical flower garden is composed of four "species" of robotic flora. Each species is an amalgamation of animal-like conduct and flower-like attributes that is put into a robotic representation that is fully aware of its surrounding environment and can respond to stimuli in a "life-like and distinct manner." Electromechanical systems hidden within the flowers' shells "allow petals to open and close and tentacles to reach or retreat in response to human movement." Soft music, varied throughout the exhibit, is played in the background as people interact with flora.
Cyberflora	The Garden	The flowers in the garden use technologies such as capacitive sensing and thermal sensors to react to human hands and bodies elsewhere in the room.
Cyberflora	Design team	Cynthia Breazeal - Project lead Jeff Lieberman - Design lead Ryan Kavanaugh - Graphic design Heather Knight - Undergraduate Blake Brasher - Undergraduate Dan McAnulty - Undergraduate
Cyberflora	Exhibits	Cyberflora was debuted in April 2003 at the National Design Triennial which was hosted by the Cooper-Hewitt, National Design Museum in New York City, New York. The exhibit began on April 22, 2003, and ended on January 25, 2004.
Mark Kittleson	Mark Kittleson	Dr. Mark J. Kittleson, Professor of Health Education at Southern Illinois University (SIU) has followed in the footsteps of his outstanding predecessors at SIU, Robert Gold and Paul Sarvela, in becoming a leader in the development of PC-based and web-based applications in health education. In 1992, he established an email discussion group that came to be known as the Health Education Directory or HEDIR, which has been called the most significant development to impact health education in the past 20 years (McDermott, 1998). Under his leadership HEDIR has given rise to the HEDIR Award, which recognizes contributions to the applications of technology to health education.
Mark Kittleson	Mark Kittleson	Dr. Kittleson was the founder and first editor, in 1998, of the International Electronic Journal of Health Education and is author of a column in the American Journal of Health Behavior, entitled "Electronic Notes," which is designed to improve understanding and utilization of technology for conducting research on health behavior. He began his professional career in health education at the Maine Health Education Resource Center, where he worked with Charles Basch under the direction of William H. Zimmerli. He then returned to school at the University of Akron, completing his Ph.D. there in 1986. He taught at Youngstown State University until 1989 when he joined the faculty of SIU.
Mark Kittleson	Mark Kittleson	Dr. Kittleson is the author of 15 books—some of the more recent have been Vital Statistics for the Public Health Educator, 2nd edition (HEDIR Publishing, 2005), Mental Health: Dimensions of Self-Esteem and Emotional Well-Being (with N. Eburne and J. Donnelly) (Allyn and Bacon Publishers, 2000), and Using Excel to Run Statistics (HEDIR Publishing, 2005). He has also published more than eighty peer-reviewed articles in such journals as the Journal of Health Education, the Journal of School Health, the Journal of Family Practice, the Southern Medical Journal, AIDS Education and Prevention, and the American Journal of Health Behavior. Most of his publications focus on needs assessment of teachers, particularly with respect to HIV/AIDS information; and the impact of the Internet and other technology on research and research communication.
Probable low affinity copper uptake protein 2	Probable low affinity copper uptake protein 2	Probable low affinity copper uptake protein 2 is a protein that in humans is encoded by the SLC31A2 gene.
Shortcut (computing)	Shortcut (computing)	In computing, a file shortcut is a handle in a user interface that allows the user to find a file or resource located in a different directory or folder from the place where the shortcut is located. Similarly, an Internet shortcut allows the user to open a page, file or resource located at a remote Internet location or Web site.
Shortcut (computing)	Shortcut (computing)	Shortcuts are typically implemented as a small file containing a target URI or GUID to an object, or the name of a target program file that the shortcut represents. The shortcut might additionally specify parameters to be passed to the target program when it is run. Each shortcut can have its own icon. Shortcuts are very commonly placed on a desktop, in an application launcher panel such as the Microsoft Windows Start menu, or in the main menu of a desktop environment. The functional equivalent in the Macintosh operating system is called an alias, and a symbolic link (or symlink) in UNIX-like systems.
Shortcut (computing)	Implementations	Microsoft Windows File shortcuts (also known as shell links) were introduced in Windows 95. Microsoft Windows uses .lnk as the filename extension for shortcuts to local files, and .URL for shortcuts to remote files, like web pages. Commonly referred to as "shortcuts" or "link files", both are displayed with a curled arrow overlay icon by default, and no filename extension. (The extension remains hidden in Windows Explorer even when "Hide extensions for known file types" is unchecked in File Type options, because it is controlled by the NeverShowExt option in HKEY_CLASSES_ROOT\lnkfile in the Registry. The IsShortcut option causes the arrow to be displayed.) Shortcut files can be used to launch programs in minimized or maximized window states if the program supports it.
Shortcut (computing)	Implementations	Microsoft Windows .lnk files operate as Windows Explorer extensions, rather than file system extensions. As a shell extension, .lnk files cannot be used in place of the file except in Windows Explorer, and have other uses in Windows Explorer in addition to use as a shortcut to a local file (or GUID). These files also begin with "L".
Shortcut (computing)	Implementations	Although shortcuts, when created, point to specific files or folders, they may break if the target is moved to another location. When a shortcut file that points to a nonexistent target is opened, Explorer will attempt to repair the shortcut. Windows 9x-based versions of Windows use a simple search algorithm to fix broken shortcuts. On Windows NT-based operating systems and the NTFS file system, the target object's unique identifier is stored in the shortcut file and Windows can use the Distributed Link Tracking service for tracking the targets of shortcuts, so that the shortcut may be silently updated if the target moves to another hard drive. Windows Installer, introduced in Windows 2000, added another special type of shortcuts called "Advertised Shortcuts." File shortcuts in Windows can store a working directory path besides the target path. Environment variables can be used. A hotkey can be defined in the shortcut's properties for shortcuts that are located in the Start Menu folders, pinned to the Taskbar or the Desktop. In Windows 2000 onwards, file shortcuts can store comments which are displayed as a tooltip when the mouse hovers over the shortcut.
Shortcut (computing)	Implementations	Generally, the effect of double-clicking a shortcut is intended to be the same as double-clicking the application or document to which it refers, but Windows shortcuts contain separate properties for the target file and the "Start In" directory. If the latter parameter is not entered, attempting to use the shortcut for some programs may generate "missing DLL" errors not present when the application is accessed directly.File system links can also be created on Windows systems (Vista and up). They serve a similar function, although they are a feature of the file system. Windows shortcuts are files and work independently of the file system, through Explorer.Beginning with Windows 7, some shortcuts also store Application User Model IDs (AppUserModelIDs). Instead of the target command line, AppUserModelIDs may directly be used to launch applications. Shortcuts with AppUserModelIDs are used by some desktop programs and all WinRT Modern/Universal Windows Platform apps for launching.
Shortcut (computing)	Implementations	Although Windows does not provide convenient tools to create it, Explorer supports a "folder link" or "shell link folder": a folder with the system attribute set, containing a hidden "desktop.ini" (folder customization) file which tells Explorer to look in that same folder for a "target.lnk" shortcut file pointing to another folder. When viewed in Explorer, the shell link folder then appears to have the contents of the target folder in it—that is, the customized folder becomes the effective shortcut. This technique is used by Microsoft Windows for items like WebDAV folders. The advent of file system links in Windows Vista and up has made shell link folders less useful.
Shortcut (computing)	Implementations	There is another type of file that is similar to a “.lnk” file, but has the extension “.cda”. This is used to reference a track (song) on a CD (in standard CDDA / RedBook format). Unix Some desktop environments for Unix-like operating systems, such as GNOME or KDE provide freedesktop.org .desktop files. These can be used to point to local or remote files, folders, and applications. Symbolic links can also be created on Unix systems, which serve a similar function, although they are a feature of the file system.
Shortcut (computing)	Implementations	List of X window managers that support .desktop shortcuts Following are some of the window managers which support the use of shortcut icons on the desktop: Mac Macintosh does not have extensions for shortcuts. A file type called "alias" was introduced in Macintosh System 7; it tracks information like inode number to handle moves. Aliases in System 7 through Mac OS 9 were distinguished from other files by using names in italics. In Mac OS 8.5 and later, another distinguishing mark was added: an "alias arrow" – a black arrow with a thin, white border – similar to that used for shortcuts in Microsoft Windows. In Mac OS X, the names of aliases are no longer italicized, but the arrow badge remains. Additionally, an alias retains its dynamic reference to an object and does not have to be specified even when calling files on remote servers.
Shortcut (computing)	Implementations	In addition, symbolic links can be created within the Unix subsystem. The Safari browser has its own property list-based format, .webloc, for storing Internet URLs.
Shortcut (computing)	History	To execute an application or render a file in early graphical user interfaces, the user had to click on the representation of the actual file or executable in the location where the application or file was. The concept of disassociating the executable from the icon representing an instruction to perform a task associated with that file or executable so that they may be grouped by function or task rather than physical organisation in the file structure was first described in the research paper "A Task Oriented Front End For The Windows Graphical User Interface", by Mike Roberts, published in 1991 by Kingston University and presented to both Microsoft and Xerox EuroPARC that same year under an academia/business technology sharing agreement. A simplified form of this research was incorporated into System 7 in 1991, and four years later into Windows 95.
Adegramotide	Adegramotide	Adegramotide (DSP-7888) is an experimental drug intended for treatment of glioblastoma multiforme. It is a peptide vaccine and, as of 2017, in phase II clinical trials.
Peripheral Sensor Interface 5	Peripheral Sensor Interface 5	Peripheral Sensor Interface (PSI5) is a digital interface for sensors. PSI5 is a two-wire interface, used to connect peripheral sensors to electronic control units in automotive electronics. Both point-to-point and bus configurations with asynchronous and synchronous data transmission are supported.
Peripheral Sensor Interface 5	Functional description	PSI5 is a current interface with modulation of the sending current for the transmission of data on the power supply lines. The relatively high sending current and the use of a Manchester code for bit encoding result in high immunity against interference from radiated emissions. The use of an inexpensive twisted pair cable is thus sufficient for most of the applications, however, in automotive more expensive cabling is employed.
Peripheral Sensor Interface 5	Functional description	Data words consist of two start bits, 8 to 24 data bits and a single parity bit or optional three bit CRC (cyclic redundancy check). The bitrate is 125 kbit/s or optionally 189 kbit/s.
Peripheral Sensor Interface 5	Standardization	Following the goal of an open interface standard, PSI5 was developed on the basis of existing proprietary implementations of the companies Autoliv, Bosch and Continental. A first common publication was released at the "Sensor" trade fair in Nuremberg in May 2005. Since summer 2006, SiemensVDO also supports the standardization of PSI5. Siemens VDO is now a part of the Continental group of companies.
Peripheral Sensor Interface 5	Standardization	IEC EMC standard for Peripheral Sensor Interface 5 (PSI5) IEC62228-6 "Integrated circuit - EMC Evaluation of transceivers - Part 6:PSI5 transceivers" is ongoing.
Current yield	Current yield	The current yield, interest yield, income yield, flat yield, market yield, mark to market yield or running yield is a financial term used in reference to bonds and other fixed-interest securities such as gilts. It is the ratio of the annual interest (coupon) payment and the bond's price: Current yield Annual interest payment Current price . According to Investopedia, the clean market price of the bond should be the denominator in this calculation.
Current yield	Example	The current yield of a bond with a face value (F) of $100 and a coupon rate (r) of 5.00% that is selling at $95.00 (clean; not including accrued interest) (P) is calculated as follows. Current Yield 100 5.00 95.00 5.00 95.00 5.2631 %
Current yield	Shortcomings of current yield	The current yield refers only to the yield of the bond at the current moment. It does not reflect the total return over the life of the bond, or the factors affecting total return, such as: the length of time over which the bond produces cash flows for the investor (the maturity date of the bond), interest earned on reinvested coupon payments, or reinvestment risk (the uncertainty about the rate at which future cash flows can be reinvested), and fluctuations in the market price of a bond prior to maturity.
Current yield	Relationship between yield to maturity and coupon rate	The concept of current yield is closely related to other bond concepts, including yield to maturity (YTM), and coupon yield. When a coupon-bearing bond sells at; a discount: YTM > current yield > coupon yield a premium: coupon yield > current yield > YTM par: YTM = current yield = coupon yield.For zero-coupon bonds selling at a discount, the coupon yield and current yield are zero, and the YTM is positive.
Broadsheet	Broadsheet	A broadsheet is the largest newspaper format and is characterized by long vertical pages, typically of 22.5 inches (57 cm). Other common newspaper formats include the smaller Berliner and tabloid–compact formats.
Broadsheet	Description	Many broadsheets measure roughly 28 by 22+3⁄4 in (711 by 578 mm) per full broadsheet spread, twice the size of a standard tabloid. Australian and New Zealand broadsheets always have a paper size of A1 per spread (841 by 594 mm or 33.1 by 23.4 in). South African broadsheet newspapers have a double-page spread sheet size of 820 by 578 mm (32.3 by 22.8 in) (single-page live print area of 380 x 545 mm). Others measure 22 in (560 mm) vertically.
Broadsheet	Description	In the United States, the traditional dimensions for the front page half of a broadsheet are 12 in (305 mm) wide by 22.75 in (578 mm) long. However, in efforts to save newsprint costs, many U.S. newspapers have downsized to 11 in (279 mm) wide by 21 in (533 mm) long for a folded page.Many rate cards and specification cards refer to the "broadsheet size" with dimensions representing the front page "half of a broadsheet" size, rather than the full, unfolded broadsheet spread. Some quote actual page size and others quote the "printed area" size.
Broadsheet	Description	The two versions of the broadsheet are: The full broadsheet typically is folded vertically in half so that it forms four pages (the front page front and back and the back page front and back). The four pages are called a spread. Inside broadsheets are nested accordingly. The half broadsheet is usually an inside page that is not folded vertically and just includes a front and back.
Broadsheet	History	The broadsheet, broadside, was used as a format for musical and popular prints in the 17th century. Eventually, people began using the broadsheet as a source for political activism by reprinting speeches.
Broadsheet	History	Broadsheet newspapers developed in Britain after a 1712 tax was imposed on newspapers based on their page counts. However, larger formats had long been signs of status in printed objects and still are in many places. Outside of Britain the broadsheet developed for other reasons unrelated to the British tax structure including style and authority. With the early mechanization of the 19th century came an increased production of printed materials including the broadside, as well as the competing penny dreadful. Newspapers all over Europe were then starting to print their issues on broadsheets. However, in the United Kingdom, the main competition for the broadside was the gradual reduction of the newspaper tax, beginning in the 1830s until its eventual dismissal in 1855.With the increased production of newspapers and literacy, the demand for visual reporting and journalists led to the blending of broadsides and newspapers, creating the modern broadsheet newspaper.
Broadsheet	Printing considerations	Modern printing facilities most efficiently print broadsheet sections in multiples of eight pages (with four front pages and four back pages). The broadsheet is then cut in half during the process. Thus, the newsprint rolls used are defined by the width necessary to print four front pages. The width of a newsprint roll is called its web. The now-common 11-inch-wide front page broadsheet newspapers in the United States use a 44-inch web newsprint roll.
Broadsheet	Printing considerations	With profit margins narrowing for newspapers in the wake of competition from broadcast, cable television, and the internet, newspapers are looking to standardize the size of the newsprint roll. The Wall Street Journal with its 12-inch-wide front page was printed on 48-inch web newsprint. Early adopters in the downsizing of broadsheets used a 50-inch web (12+1⁄2-inch front pages). However, the 48-inch web is now rapidly becoming the definitive standard in the U.S. The New York Times held out on the downsizing until July 2006, saying it would stick to its 54-inch web (13+1⁄2-inch front page). However, the paper adopted the narrower format beginning Monday, 6 August 2007.
Broadsheet	Printing considerations	The smaller newspapers also have the advantage of being easier to handle, particularly among commuters.
Broadsheet	Connotations	In some countries, especially Australia, Canada, the UK, and the US, broadsheet newspapers are commonly perceived to be more intellectual in content than their tabloid counterparts. They tend to use their greater size to publish stories exploring topics in-depth and carry less sensationalist and celebrity-oriented material. The distinction is most obvious on the front page since tabloids tend to have a single story dominated by a headline, and broadsheets allow two or more stories to be displayed of which the most important sit at the top of the page "above the fold." A few newspapers, though, such as the German Bild-Zeitung and others throughout Central Europe are tabloids in terms of content but use the physical broadsheet format.
Broadsheet	Switch to smaller sizes	In the United Kingdom In 2003, The Independent started concurrent production of both broadsheet and tabloid ("compact") editions, carrying exactly the same content. The Times did likewise, but with less apparent success, with readers vocally opposing the change. The Independent ceased to be available in broadsheet format in May 2004, and The Times followed suit from November 2004; The Scotsman is also now published only in tabloid format. The Guardian switched to the "Berliner" or "midi" format found in some other European countries (slightly larger than a traditional tabloid) on 12 September 2005. In June 2017, the Guardian announced it would again change the format to tabloid size – the first tabloid edition was published on 15 January 2018.
Broadsheet	Switch to smaller sizes	The main motivation cited for this shift was that commuters prefer papers that they can hold easily on public transport and that other readers also might find the smaller formats more convenient.
Broadsheet	Switch to smaller sizes	In the United States In the United States, The Wall Street Journal made headlines when it announced its overseas version would convert to a tabloid on 17 October 2005. Strong debate occurred in the US on whether or not the rest of the national papers will or even should follow the trend of the European papers and The Wall Street Journal. The Wall Street Journal overseas edition switched back to a broadsheet format in 2015.
Parkinson-plus syndrome	Parkinson-plus syndrome	Parkinson-plus syndromes (PPS) are a group of neurodegenerative diseases featuring the classical features of Parkinson's disease (tremor, rigidity, akinesia/bradykinesia, and postural instability) with additional features that distinguish them from simple idiopathic Parkinson's disease (PD). Parkinson-plus syndromes are either inherited genetically or occur sporadically.Atypical parkinsonism and other Parkinson-plus syndromes are often difficult to differentiate from PD and each other. They include multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD). Dementia with Lewy bodies (DLB), may or may not be part of the PD spectrum, but it is increasingly recognized as the second-most common type of neurodegenerative dementia after Alzheimer's disease. These disorders are currently lumped into two groups, the synucleinopathies and the tauopathies. They may coexist with other pathologies.Additional Parkinson-plus syndromes include Pick's disease and olivopontocerebellar atrophy. The latter is characterized by ataxia and dysarthria, and may occur either as an inherited disorder or as a variant of multiple system atrophy. MSA is also characterized by autonomic failure, formerly known as Shy–Drager syndrome.
Parkinson-plus syndrome	Presentation	Clinical features that distinguish Parkinson-plus syndromes from idiopathic PD include symmetrical onset, a lack of or irregular resting tremor, and a reduced response to dopaminergic drugs (including levodopa). Additional features include bradykinesia, early-onset postural instability, increased rigidity in axial muscles, dysautonomia, alien limb syndrome, supranuclear gaze palsy, apraxia, involvement of the cerebellum including the pyramidal cells, and in some instances significant cognitive impairment.
Parkinson-plus syndrome	Diagnosis	Accurate diagnosis of these Parkinson-plus syndromes is improved when precise diagnostic criteria are used. Since diagnosis of individual Parkinson-plus syndromes is difficult, the prognosis is often poor. Proper diagnosis of these neurodegenerative disorders is important as individual treatments vary depending on the condition. The nuclear medicine SPECT procedure using 123I‑iodobenzamide (IBZM), is an effective tool in the establishment of the differential diagnosis between patients with PD and Parkinson-plus syndromes.
Parkinson-plus syndrome	Treatments	Parkinson-plus syndromes are usually more rapidly progressive and less likely to respond to antiparkinsonian medication than PD. However, the additional features of the diseases may respond to medications not used in PD.Current therapy for Parkinson-plus syndromes is centered around a multidisciplinary treatment of symptoms.
Sotoarc	Sotoarc	Sotoarc is a commercial static code analysis tool for software architects. It graphically visualizes the static structure of software systems written in Java, C# or in C++ code. The code structure is displayed as hierarchies (trees) of modules, packages and files. Besides the user can describe by graphical means the specified software architecture of a software system. By doing so the tool is immediately comparing this intended architecture with the implemented code structure and is highlighting all architecture violations (i.e. all code references and dependencies which do not correspond to the intended architecture.) As an add-on tool to Sotoarc an Eclipse plug-in is able to do the architecture conformance check directly in Eclipse. This plug-in informs the developer immediately when he has just implemented code which is violating architecture constraints.
Pulmonary heart disease	Pulmonary heart disease	Pulmonary heart disease, also known as cor pulmonale, is the enlargement and failure of the right ventricle of the heart as a response to increased vascular resistance (such as from pulmonic stenosis) or high blood pressure in the lungs.Chronic pulmonary heart disease usually results in right ventricular hypertrophy (RVH), whereas acute pulmonary heart disease usually results in dilatation. Hypertrophy is an adaptive response to a long-term increase in pressure. Individual muscle cells grow larger (in thickness) and change to drive the increased contractile force required to move the blood against greater resistance. Dilatation is a stretching (in length) of the ventricle in response to acute increased pressure.To be classified as pulmonary heart disease, the cause must originate in the pulmonary circulation system; RVH due to a systemic defect is not classified as pulmonary heart disease. Two causes are vascular changes as a result of tissue damage (e.g. disease, hypoxic injury), and chronic hypoxic pulmonary vasoconstriction. If left untreated, then death may result. The heart and lungs are intricately related; whenever the heart is affected by a disease, the lungs risk following and vice versa.
Pulmonary heart disease	Signs and symptoms	The symptoms/signs of pulmonary heart disease (cor pulmonale) can be non-specific and depend on the stage of the disorder, and can include blood backing up into the systemic venous system, including the hepatic vein. As pulmonary heart disease progresses, most individuals will develop symptoms like: Shortness of breath Wheezing Cyanosis Ascites Jaundice Enlargement of the liver Raised jugular venous pressure (JVP) Third heart sound Intercostal recession Presence of abnormal heart sounds
Pulmonary heart disease	Causes	The causes of pulmonary heart disease (cor pulmonale) are the following: Acute respiratory distress syndrome (ARDS) COPD Primary pulmonary hypertension Blood clots in lungs Kyphoscoliosis Interstitial lung disease Cystic fibrosis Sarcoidosis Obstructive sleep apnea (untreated) Sickle cell anemia Bronchopulmonary dysplasia (in infants)
Pulmonary heart disease	Pathophysiology	The pathophysiology of pulmonary heart disease (cor pulmonale) has always indicated that an increase in right ventricular afterload causes RV failure (pulmonary vasoconstriction, anatomic disruption/pulmonary vascular bed and increased blood viscosity are usually involved), however most of the time, the right ventricle adjusts to an overload in chronic pressure. According to Voelkel, et al., pressure overload is the initial step for changes in RV, other factors include: Ischemia Inflammation Oxidative damage Epigenetics Abnormal cardiac energetics
Pulmonary heart disease	Diagnosis	Investigations available to determine the cause of cor pulmonale include the following: Chest x-ray – right ventricular hypertrophy, right atrial dilatation, prominent pulmonary artery ECG – right ventricular hypertrophy, dysrhythmia, P pulmonale (characteristic peaked P wave) Thrombophilia screen- to detect chronic venous thromboembolism (proteins C and S, antithrombin III, homocysteine levels) Differential diagnosis The diagnosis of pulmonary heart disease is not easy as both lung and heart disease can produce similar symptoms. Therefore, the differential diagnosis (DDx) should assess: Atrial myxoma Congestive heart failure Constrictive pericarditis Infiltrative cardiomyopathies Right heart failure (right ventricular infarction) Ventricular septal defect
Pulmonary heart disease	Treatment	The treatment for cor pulmonale can include the following: antibiotics, expectorants, oxygen therapy, diuretics, digitalis, vasodilators, and anticoagulants. Some studies have indicated that Shenmai injection with conventional treatment is safe and effective for cor pulmonale (chronic).Treatment requires diuretics (to decrease strain on the heart). Oxygen is often required to resolve the shortness of breath. Additionally, oxygen to the lungs also helps relax the blood vessels and eases right heart failure. When wheezing is present, the majority of individuals require a bronchodilator. A variety of medications have been developed to relax the blood vessels in the lung, calcium channel blockers are used but only work in few cases and according to NICE are not recommended for use at all.Anticoagulants are used when venous thromboembolism is present. Venesection is used in severe secondary polycythemia (because of hypoxia), which improves symptoms though survival rate has not been proven to increase. Finally, transplantation of single/double lung in extreme cases of cor pulmonale is also an option.
Pulmonary heart disease	Epidemiology	The epidemiology of pulmonary heart disease (cor pulmonale) accounts for 7% of all heart disease in the U.S According to Weitzenblum, et al., the mortality that is related to cor pulmonale is not easy to ascertain, as it is a complication of COPD.
ConnectiCon	ConnectiCon	ConnectiCon is an annual multi-genre convention dedicated to "a celebration of pop culture - everything from anime, to science fiction, comic books, and card games."
ConnectiCon	Events	The convention includes 24-hour screening rooms of full-length features and episodes of classic and modern science fiction and anime titles and sponsorship by GameStop, which also provides consoles for tournament and casual video gaming.Gaming, including board, card, miniature and role-playing are featured. The convention also features an "artist alley" an art show, an exhibitor hall, panels and workshops throughout the convention as well as larger events on a theatrical level such the Masquerade, Cosplay Chess, Death Match, Dating Game, and Nerd Prom. Other entertainment includes artistic, musical and theatrical guest performances such as from Super Art Fight.
ConnectiCon	Past guests	Past guests of honor have included popular voice actors for anime and video games, such as Carlos Ferro, and film and television actors, such as Robert Picardo, Ethan Phillips, Ellen Muth, Glenn Shadix, and Peter Mayhew. Prominent web comic personalities have also been in attendance, such as Brian Clevinger of 8-Bit Theater, Scott Ramsoomair of VG Cats, Tim Buckley of Ctrl+Alt+Del, and Ananth Hirsh and Mohammad "Hawk" Haque of Applegeeks. The convention has been held in the Connecticut Convention Center in Hartford since 2005, after having been held at the University of Hartford from its inception in 2003. The convention has grown in size every year since, with over 12,000 paid attendees as of 2016.Guests in 2018 included Cal Dodd, Troy Baker, Linda Ballantyne, Steve Blum, Jason Fry, Katie Griffin, Deedee Magno Hall, Vanessa Marshall, Nolan North, Ron Rubin, and Jon St. John.
Optional stopping theorem	Optional stopping theorem	In probability theory, the optional stopping theorem (or sometimes Doob's optional sampling theorem, for American probabilist Joseph Doob) says that, under certain conditions, the expected value of a martingale at a stopping time is equal to its initial expected value. Since martingales can be used to model the wealth of a gambler participating in a fair game, the optional stopping theorem says that, on average, nothing can be gained by stopping play based on the information obtainable so far (i.e., without looking into the future). Certain conditions are necessary for this result to hold true. In particular, the theorem applies to doubling strategies.
Optional stopping theorem	Optional stopping theorem	The optional stopping theorem is an important tool of mathematical finance in the context of the fundamental theorem of asset pricing.
Optional stopping theorem	Statement	A discrete-time version of the theorem is given below: Let X = (Xt)t∈ N 0 be a discrete-time martingale and τ a stopping time with values in N 0 ∪ {∞}, both with respect to a filtration (Ft)t∈ N 0. Assume that one of the following three conditions holds: (a) The stopping time τ is almost surely bounded, i.e., there exists a constant c ∈ N such that τ ≤ c a.s.
Optional stopping theorem	Statement	(b) The stopping time τ has finite expectation and the conditional expectations of the absolute value of the martingale increments are almost surely bounded, more precisely, E[τ]<∞ and there exists a constant c such that E[\|Xt+1−Xt\|\|Ft]≤c almost surely on the event {τ > t} for all t ∈ N 0. (c) There exists a constant c such that \|Xt∧τ\| ≤ c a.s. for all t ∈ N 0 where ∧ denotes the minimum operator.Then Xτ is an almost surely well defined random variable and E[Xτ]=E[X0]. Similarly, if the stochastic process X = (Xt)t∈ N 0 is a submartingale or a supermartingale and one of the above conditions holds, then E[Xτ]≥E[X0], for a submartingale, and E[Xτ]≤E[X0], for a supermartingale. In the previous paragraphs, N denotes the set of natural integers, including zero. Remark Under condition (c) it is possible that τ = ∞ happens with positive probability. On this event Xτ is defined as the almost surely existing pointwise limit of (Xt)t∈ N 0 , see the proof below for details.
Optional stopping theorem	Applications	The optional stopping theorem can be used to prove the impossibility of successful betting strategies for a gambler with a finite lifetime (which gives condition (a)) or a house limit on bets (condition (b)). Suppose that the gambler can wager up to c dollars on a fair coin flip at times 1, 2, 3, etc., winning his wager if the coin comes up heads and losing it if the coin comes up tails. Suppose further that he can quit whenever he likes, but cannot predict the outcome of gambles that haven't happened yet. Then the gambler's fortune over time is a martingale, and the time τ at which he decides to quit (or goes broke and is forced to quit) is a stopping time. So the theorem says that E[Xτ] = E[X0]. In other words, the gambler leaves with the same amount of money on average as when he started. (The same result holds if the gambler, instead of having a house limit on individual bets, has a finite limit on his line of credit or how far in debt he may go, though this is easier to show with another version of the theorem.) Suppose a random walk starting at a ≥ 0 that goes up or down by one with equal probability on each step. Suppose further that the walk stops if it reaches 0 or m ≥ a; the time at which this first occurs is a stopping time. If it is known that the expected time at which the walk ends is finite (say, from Markov chain theory), the optional stopping theorem predicts that the expected stop position is equal to the initial position a. Solving a = pm + (1 – p)0 for the probability p that the walk reaches m before 0 gives p = a/m.
Optional stopping theorem	Applications	Now consider a random walk X that starts at 0 and stops if it reaches –m or +m, and use the Yn = Xn2 – n martingale from the examples section. If τ is the time at which X first reaches ±m, then 0 = E[Y0] = E[Yτ] = m2 – E[τ]. This gives E[τ] = m2.
Optional stopping theorem	Applications	Care must be taken, however, to ensure that one of the conditions of the theorem hold. For example, suppose the last example had instead used a 'one-sided' stopping time, so that stopping only occurred at +m, not at −m. The value of X at this stopping time would therefore be m. Therefore, the expectation value E[Xτ] must also be m, seemingly in violation of the theorem which would give E[Xτ] = 0. The failure of the optional stopping theorem shows that all three of the conditions fail.
Optional stopping theorem	Proof	Let Xτ denote the stopped process, it is also a martingale (or a submartingale or supermartingale, respectively). Under condition (a) or (b), the random variable Xτ is well defined. Under condition (c) the stopped process Xτ is bounded, hence by Doob's martingale convergence theorem it converges a.s. pointwise to a random variable which we call Xτ.
Optional stopping theorem	Proof	If condition (c) holds, then the stopped process Xτ is bounded by the constant random variable M := c. Otherwise, writing the stopped process as Xtτ=X0+∑s=0τ−1∧t−1(Xs+1−Xs),t∈N0, gives \|Xtτ\| ≤ M for all t ∈ N 0, where := \|X0\|+∑s=0τ−1\|Xs+1−Xs\|=\|X0\|+∑s=0∞\|Xs+1−Xs\|⋅1{τ>s} .By the monotone convergence theorem E[M]=E[\|X0\|]+∑s=0∞E[\|Xs+1−Xs\|⋅1{τ>s}] .If condition (a) holds, then this series only has a finite number of non-zero terms, hence M is integrable.
Optional stopping theorem	Proof	If condition (b) holds, then we continue by inserting a conditional expectation and using that the event {τ > s} is known at time s (note that τ is assumed to be a stopping time with respect to the filtration), hence a.s. by (b) ]≤E[\|X0\|]+c∑s=0∞P(τ>s)=E[\|X0\|]+cE[τ]<∞, where a representation of the expected value of non-negative integer-valued random variables is used for the last equality.
Optional stopping theorem	Proof	Therefore, under any one of the three conditions in the theorem, the stopped process is dominated by an integrable random variable M. Since the stopped process Xτ converges almost surely to Xτ, the dominated convergence theorem implies lim t→∞E[Xtτ]. By the martingale property of the stopped process, E[Xtτ]=E[X0],t∈N0, hence E[Xτ]=E[X0]. Similarly, if X is a submartingale or supermartingale, respectively, change the equality in the last two formulas to the appropriate inequality.
Retina display	Retina display	The Retina display is a branded series of IPS LCD and OLED displays by Apple Inc. and have a higher pixel density than its traditional displays. Apple has registered the term "Retina" as a trademark with regard to computers and mobile devices with the United States Patent and Trademark Office and Canadian Intellectual Property Office. The applications were approved in 2012 and 2014 respectively. The Canadian application cited a 2010 application in Jamaica.
Retina display	Retina display	The Retina display debuted in 2010 with the iPhone 4 and the iPod Touch (4th Generation), and later the iPad (3rd generation) where each screen pixel of the iPhone 3GS, iPod touch (3rd generation), and the iPad 2 was replaced by four smaller pixels, and the user interface scaled up to fill in the extra pixels. Apple calls this mode HiDPI mode. In simpler words, it is one logical pixel corresponds to four physical pixels. The scale factor is tripled for devices with even higher pixel densities, such as the iPhone 6 Plus and iPhone X. The advantage of this equation is that the CPU "sees" a small portion of the data and calculates the relative positions of each element, and the GPU renders these elements with high quality assets. The goal of Retina displays is to make the text and images being displayed more crisp.The Retina display has since expanded to most Apple product lines, such as Apple Watch, iPhone, iPod Touch, iPad, iPad Mini, iPad Air, iPad Pro, MacBook, MacBook Air, MacBook Pro, iMac, and Pro Display XDR, some of which have never had a comparable non-Retina display. Apple uses various marketing terms to differentiate between its LCD and OLED displays having various resolutions, contrast levels, color reproduction, or refresh rates. It is known as Liquid Retina display for the iPhone XR, iPad Air 4th Generation, iPad Mini 6th Generation, iPad Pro 3rd Generation and later versions, and Retina 4.5K display for the iMac.Apple's Retina displays are not an absolute standard for display sharpness, but vary depending on the size of the display on the device, and at what distance the user would typically be viewing the screen. Where on smaller devices with smaller displays users would view the screen at a closer distance to their eyes, the displays have more PPI (Pixels Per Inch), while on larger devices with larger displays where the user views the screen further away, the screen uses a lower PPI value. Later device versions have had additional improvements, whether an increase in the screen size (the iPhone Xs Max), contrast ratio (the 12.9” iPad Pro 5th Generation, and iMac with Retina 4.5K display), and/or, more recently, PPI count (OLED iPhones); as a result, Apple uses the names “Retina HD display", "Retina 4K/5K display", “Retina 4.5K display", "Super Retina HD display", “Super Retina XDR display”, and "Liquid Retina display" for each successive version.
Retina display	Rationale	When introducing the iPhone 4, Steve Jobs said the number of pixels needed for a Retina display is about 300 PPI for a device held 10 to 12 inches from the eye. One way of expressing this as a unit is pixels-per-degree (PPD) which takes into account both the screen resolution and the distance from which the device is viewed. Based on Jobs' predicted number of 300, the threshold for a Retina display starts at the PPD value of 57 PPD. 57 PPD means that a tall skinny triangle with a height equal to the viewing distance and a top angle of one degree will have a base on the device's screen that covers 57 pixels. Note that the PPD parameter is not an intrinsic parameter of the display itself, unlike absolute pixel resolution (e.g. 1920×1080 pixels) or relative pixel density (e.g. 401 PPI), but is dependent on the distance between the display and the eye of the person (or lens of the device) viewing the display; moving the eye closer to the display reduces the PPD, and moving away from it increases the PPD in proportion to the distance.
Retina display	Rationale	It can be calculated by the formula tan 0.5 ∘) where d is the distance to the screen and r is the resolution of the screen in pixels per unit length.
Retina display	Rationale	In practice, thus far Apple has converted a device's display to Retina by doubling the number of pixels in each direction, quadrupling the total resolution. This increase creates a sharper interface at the same physical dimensions. The only exceptions to this have been the iPhone 6 Plus, 6S Plus, 7 Plus, and 8 Plus, which render their displays at triple the number of pixels in each direction, before down-sampling to a 1080p resolution.
Retina display	Models	The displays are manufactured worldwide by different suppliers. Currently, the iPad's display comes from Samsung, while the MacBook Pro and iPod Touch displays are made by LG Display and Japan Display Inc. There was a shift of display technology from twisted nematic (TN) liquid-crystal displays (LCDs) to in-plane switching (IPS) LCDs starting with the iPhone 4 models in June 2010.
Retina display	Models	Apple markets the following devices as having a Retina display, Retina HD display, Liquid Retina display, Liquid Retina XDR display, Super Retina HD display, Super Retina XDR display or Retina 4K/5K/6K display:
Retina display	Reception	Reviews of Apple devices with Retina displays have generally been positive on technical grounds, with comments describing it as a considerable improvement on earlier screens and praising Apple for driving third-party application support for high-resolution displays more effectively than on Windows. While high-dpi displays such as IBM's T220 and T221 had been sold in the past, they had seen little take-up due to their cost of around $8400.Reviewing the iPhone 4 in 2010, Joshua Topolsky commented: "to our eyes, there has never been a more detailed, clear, or viewable screen on any mobile device. Not only are the colors and blacks deep and rich, but you simply cannot see pixels on the screen…webpages that would be line after line of pixelated content when zoomed out on a 3GS are completely readable on the iPhone 4, though the text is beyond microscopic." Former Microsoft employee Bill Hill, an expert on font rendering, offered similar comments: That much resolution is stunning. To see it on a mainstream device like the iPad—rather than a $13,000 exotic monitor—is truly amazing, and something I've been waiting more than a decade to see. It will set a bar for future resolution that every other manufacturer of devices and PCs will have to jump.
Retina display	Reception	Writer John Gruber suggested that the arrival of Retina displays on computers would trigger a need to redesign interfaces and designs for the new displays: The sort of rich, data-dense information design espoused by Edward Tufte can now not only be made on the computer screen but also enjoyed on one. Regarding font choices, you not only need not choose a font optimized for rendering on screen, but should not. Fonts optimized for screen rendering look cheap on the retina MacBook Pro—sometimes downright cheesy—in the same way they do when printed in a glossy magazine.
Retina display	Detractors	Raymond Soneira, president of DisplayMate Technologies, has challenged Apple's claim. He says that the physiology of the human retina is such that there must be at least 477 pixels per inch in a pixelated display for the pixels to become imperceptible to the human eye at a distance of 12 inches (305 mm). Astronomer and science blogger Phil Plait notes, however, that, "if you have [better than 20/20] eyesight, then at one foot away the iPhone 4S's pixels are resolved. The picture will look pixelated. If you have average eyesight [20/20 vision], the picture will look just fine... So in my opinion, what Jobs said was fine. Soneira, while technically correct, was being picky." The retinal neuroscientist Bryan Jones offers a similar analysis of more detail and comes to a similar conclusion: "I'd find Apple's claims stand up to what the human eye can perceive."Apple fan website CultOfMac hosts an article by John Brownlee who incorrectly stated that the resolution the human eye can discern at 12 inches is 900 PPI, concluding "Apple's Retina Displays are only about 33% of the way there." On the topic of 20/20 vision, Brownlee misrepresented visual acuity in the population saying "most research suggests that normal vision is actually much better than 20/20" when in truth the majority have worse than 20/20 vision, and the WHO considers average vision as 20/40. Brownlee also stated that people do not always view displays at a constant distance, and claimed a close-viewed display could no longer be classed as Retina. However, near visual acuity is usually poor due to presbyopia in nearly everyone over 40, such that decreasing reading distance can actually reduce perceivable resolution.
Retina display	Competitors	The first smartphone following the iPhone 4 to ship with a display of a comparable pixel density was the Nokia E6, running Symbian Anna, with a resolution of 640 × 480 at a screen size of 62.5mm. This was an isolated case for the platform however, as all other Symbian-based devices had larger displays with lower resolutions. Some older Symbian smartphones, including the Nokia N80 and N90, featured a 2.1 inch display at 259 ppi, which was one of the sharpest at the time. The first Android smartphones with the same display - Meizu M9 was launched a few months later in beginning of 2011. In October of the same year Galaxy Nexus was announced, which had a display with a better resolution. By 2013 the 300+ ppimark was found on midrange phones such as the Moto G. From 2013 to 2014, many flagship devices such as the Samsung Galaxy S4 and HTC One (M8) had 1080p (FHD) screens around 5-inches for a 400+ PPI which surpassed the Retina density on the iPhone 5. The second major redesign of the iPhone, the iPhone 6, has a 1334 × 750 resolution on a 4.7-inch screen, while rivals such as the Samsung Galaxy S6 have a QHD display of 2560 × 1440 resolution, close to four times the number of pixels found in the iPhone 6, giving the S6 a 577 PPI that is almost twice that of the iPhone 6's 326 PPI. The Sony Xperia Z5 Premium launched in late 2015 had 806 PPI.
Retina display	Competitors	The larger iPhone 6 Plus features a "Retina HD display", which is a 5.5-inch 1080p screen with 401 PPI. Aside from resolution, all generations of iPhone Retina displays receive high ratings for other aspects such as brightness and color accuracy, compared to those of contemporary smartphones, while some Android devices such as the LG G3 have sacrificed screen quality and battery life for high resolution. Ars Technica suggested the "superfluousness of so many flagship phone features—the move from 720p to 1080p to 1440p and beyond...things are all nice to have, but you’d be hard-pressed to argue that any of them are essential". Furthermore, developers can better optimize content for iOS due to Apple's few screen sizes in contrast to Android's wide display format variations.Many Windows-based Ultrabook models have offered 1080p (FHD) screens standard since 2012 and often QHD or QHD+ as optional upgrade displays.
Halt and Catch Fire (computing)	Halt and Catch Fire (computing)	In computer engineering, Halt and Catch Fire, known by the assembly mnemonic HCF, is an idiom referring to a computer machine code instruction that causes the computer's central processing unit (CPU) to cease meaningful operation, typically requiring a restart of the computer. It originally referred to a fictitious instruction in IBM System/360 computers (introduced in 1964), making a joke about its numerous non-obvious instruction mnemonics.
Halt and Catch Fire (computing)	Halt and Catch Fire (computing)	With the advent of the MC6800 (introduced in 1974), a design flaw was discovered by programmers. Due to incomplete opcode decoding, two illegal opcodes, 0x9D and 0xDD, will cause the program counter on the processor to increment endlessly, which locks the processor until reset. Those codes have been unofficially named HCF. During the design process of the MC6802, engineers originally planned to remove this instruction, but kept it as-is for testing purposes. As a result, HCF was officially recognized as a real instruction. Later, HCF became a humorous catch-all term for instructions that may freeze a processor, including intentional instructions for testing purposes, and unintentional illegal instructions. Some are considered hardware defects, and if the system is shared, a malicious user can execute it to launch a denial-of-service attack.
Halt and Catch Fire (computing)	Halt and Catch Fire (computing)	In the case of real instructions, the implication of this expression is that, whereas in most cases in which a CPU executes an unintended instruction (a bug in the code) the computer may still be able to recover, in the case of an HCF instruction there is, by definition, no way for the system to recover without a restart. The expression catch fire is a facetious exaggeration of the speed with which the CPU chip would be switching some bus circuits, causing them to overheat and burn.
Halt and Catch Fire (computing)	Origins	The Z1 (1938) and Z3 (1941) computers built by Konrad Zuse contained illegal sequences of instructions which damaged the hardware if executed by accident.Apocryphal stories connect this term with an illegal opcode in IBM System/360. A processor, upon encountering the instruction, would start switching bus lines very fast, potentially leading to overheating.In a computer's assembly language, mnemonics are used that are directly equivalent to machine code instructions. The mnemonics are frequently three letters long, such as ADD, CMP (to compare two numbers), and JMP (jump to a different location in the program). The HCF instruction was originally a fictitious assembly language instruction, said to be under development at IBM for use in their System/360 computers, along with many other amusing three-letter acronyms like XPR (Execute Programmer) and CAI (Corrupt Accounting Information), and similar to other joke mnemonics such as "SDI" for "Self Destruct Immediately" and "CRN" for "Convert to Roman Numerals". A list of such mnemonics, including HCF, shows up as "Overextended Mnemonics" in the April 1980 Creative Computing flip-side parody issue.

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