A software bug is an error, flaw, mistake, failure, or fault in a computer program that prevents it from behaving as intended (e.g., producing an incorrect result). Most bugs arise from mistakes and errors made by people in either a program's source code or its design, and a few are caused by compilers producing incorrect code. A program that contains a large number of bugs, and/or bugs that seriously interfere with its functionality, is said to be buggy. Reports detailing bugs in a program are commonly known as bug reports, fault reports, problem reports, trouble reports, change requests, and so forth. To meet Wikipedias quality standards, this article or section may require cleanup. ... A computer program is a collection of instructions that describe a task, or set of tasks, to be carried out by a computer. ... Source code (commonly just source or code) is any series of statements written in some human-readable computer programming language. ... The software architecture of a system consists of software components, their external properties, and their relationships with one another. ... This article is about the computing term. ...

Bugs can have a wide variety of effects, with varying levels of inconvenience to the user of the program. Some bugs have only a subtle effect on the program's functionality, and may thus lie undetected for a long time. More serious bugs may cause the program to crash or freeze leading to a denial of service. Others qualify as security bugs and might for example enable a malicious user to bypass access controls in order to obtain unauthorized privileges. A crash in computing is a condition where a program (either an application or part of the operating system) stops performing its expected function and also stops responding to other parts of the system. ... See Hang. ... A denial-of-service attack (also, DoS attack) is an attack on a computer system or network that causes a loss of service to users, typically the loss of network connectivity and services by consuming the bandwidth of the victim network or overloading the computational resources of the victim system. ... A security bug is a software bug that benefits someone other than intended beneficiaries in the intended ways. ... In the context of computer networking, cracking (also called black-hat hacking) is the act of compromising the security of a system without permission from an authorized party, usually with the intent of accessing computers connected to the network. ... In security, specifically physical security, the term access control refers to the practice of restricting entrance to a property, a building, or a room to authorized persons. ...

The results of bugs may be extremely serious. A bug in the code controlling the Therac-25 radiation therapy machine was directly responsible for some patient deaths and in 1996, the European Space Agency's US$1 billion prototype Ariane 5 rocket was destroyed less than a minute after launch, due to a bug in the on-board guidance computer program. In June 1994, a Royal Air Force Chinook crashed into the Mull of Kintyre, killing 29. This was initially dismissed as pilot error, but an investigation by Computer Weekly uncovered sufficient evidence to convince a House of Lords enquiry that it may have been caused by a software bug in the aircraft's FADEC. [2] [3] Therac-25 was a radiation therapy machine produced by Atomic Energy of Canada Limited. ... Clinac 2100 C100 accelerator Radiation therapy (or radiotherapy) is the medical use of ionizing radiation as part of cancer treatment to control malignant cells (not to be confused with radiology, the use of radiation in medical imaging and diagnosis). ... ESA redirects here. ... Prototypes or prototypical instances combine the most representative attributes of a category. ... Ariane 5 mock-up Ariane 5 is a European expendable launch system designed to deliver satellites into geostationary transfer orbit and to send payloads to Low Earth orbit. ... The Royal Air Force (RAF) is the air force branch of the British Armed Forces. ... The Boeing CH-47 Chinook is a versatile, twin-engine, tandem rotor heavy-lift helicopter. ... A mull is an almost exclusively Scottish term for the geographic feature known as a promontory and, often more specifically, for the tip of that promontory or peninsula. ... Pilot error is a term used to describe the cause of a crash of an airworthy aircraft where the pilot is considered to be principally or partially at fault. ... (Actually titled ComputerWeekly on the magazine). ... This article is about the British House of Lords. ... FADEC is the acronym for Full Authority Digital Engine Control. ...

Etymology

The concept that software might contain errors dates back to 1842 in Ada Byron's notes on the analytical engine in which she speaks of the difficulty of preparing program 'cards' for Charles Babbage's Analytical engine: In 1840 Charles Babbage was invited to give a seminar at the University of Turin about his analytical engine. ... Charles Babbage (26 December 1791 – 18 October 1871) was an English mathematician, philosopher, mechanical engineer and (proto-) computer scientist who originated the idea of a programmable computer. ... The analytical engine, an important step in the history of computers, is the design of a mechanical modern general-purpose computer by the British professor of mathematics Charles Babbage. ...

Usage of the term "bug" to describe inexplicable defects has been a part of engineering jargon for many decades and predates computers and computer software; it may have originally been used in hardware engineering to describe mechanical malfunctions. For instance, Thomas Edison wrote the following words in a letter to an associate in 1878: Thomas Alva Edison (February 11, 1847 – October 18, 1931) was an American inventor and businessman who developed many devices which greatly influenced life worldwide into the 21st century. ... 1878 (MDCCCLXXVIII) was a common year starting on Tuesday (see link for calendar). ...

Problems with radar electronics during World War II were referred to as bugs (or glitches), and there is additional evidence that the usage dates back much earlier. This long range Radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll[1]. Radar is a system that uses radio waves to determine and map the location, direction, and/or speed... Combatants Allied Powers: United Kingdom France Soviet Union United States Republic of China and others Axis Powers: Germany Italy Japan and others Commanders Winston Churchill Charles de Gaulle Joseph Stalin Franklin Roosevelt Chiang Kai-Shek Adolf Hitler Benito Mussolini Hideki Tojo Casualties Military dead: 17,000,000 Civilian dead: 33...

Photo of what is possibly the first actual bug found in a computer.

The invention of the term is often erroneously attributed to Grace Hopper, who publicized the cause of a malfunction in an early electromechanical computer. A typical version of the story is given by this quote: Download high resolution version (740x615, 93 KB)Photo of first Computer bug, public domain image from US Navy. ... Download high resolution version (740x615, 93 KB)Photo of first Computer bug, public domain image from US Navy. ... Grace Hopper Rear Admiral Grace Murray Hopper (December 9, 1906 – January 1, 1992) was an American computer scientist and naval officer. ...

Hopper was not actually the one who found the insect, as she readily acknowledged. And the date was September 9, 1947, not of 1945 [4] [5]. The operators who did find it (including William "Bill" Burke, later of the Naval Weapons Laboratory, Dahlgren Va. ^[3]), were familiar with the engineering term and, amused, kept the insect with the notation "First actual case of bug being found." Hopper loved to recount the story. [6] September 9 is the 252nd day of the year (253rd in leap years). ... Year 1947 (MCMXLVII) was a common year starting on Wednesday (the link is to a full 1947 calendar). ...

While it is certain that the Mark II operators did not coin the term "bug", it has been suggested that they did coin the related term, "debug". The Harvard Mark II was an electromechanical computer built at Harvard University under the direction of Howard Aiken and was finished in 1947. ... Debugging is a methodical process of finding and reducing the number of bugs, or defects, in a computer program or a piece of electronic hardware thus making it behave as expected. ...

Prevention

It can be psychologically difficult for some engineers to accept that their design contains bugs. They may hide behind euphemisms like "issues" or "unplanned/unexpected/undocumented features". This is also true of corporate software where a fix for a bug is often called "a reliability enhancement".

Bugs are a consequence of the nature of the programming task. Some bugs arise from simple oversights made when computer programmers write source code carelessly or transcribe data incorrectly. Many off-by-one errors fall into this category. Other bugs arise from unintended interactions between different parts of a computer program. This happens because computer programs are often complex, often having been programmed by several different people over a great length of time, so that programmers are unable to mentally keep track of every possible way in which different parts can interact. Many race condition bugs fall into this category. In computing, a programmer is someone who does computer programming and develops computer software. ... Source code (commonly just source or code) is any series of statements written in some human-readable computer programming language. ... An off-by-one error in computer programming is an avoidable error in which a loop iterates one too many or one too few times than desired. ... A race hazard (or race condition) is a flaw in a system or process where the output exhibits unexpected critical dependence on the relative timing of events. ...

The computer software industry has put a great deal of effort into finding methods for preventing programmers from inadvertently introducing bugs while writing software. These include:

Programming style 

Bugs are often created by typos that are not caught by the compiler. Some innovations to programming style such as indentation, clearly-distinguished variable names, vertically aligning similar blocks, and so forth, are designed to make these bugs less likely, or easier to spot. In curly bracket programming languages, it has become common for style documents to require that even where optional, curly brackets be placed after all control flow constructs. This prevents program-flow bugs which can be very time-consuming to track down, such as where a terminating semicolon is introduced at the end of the construct (a common typo); where another line is added before the first; or where the following line may be removed by the preprocessor. Other examples of using style to prevent bugs include placing constants on the left hand side in comparisons, (which causes a syntax error in the case of the common typo of replacing the comparison operator "==" with the assignment operator "="); placing a comma after even the last element of a list, and the last line in a block, where these are normally optional; etc.

Programming techniques 

Bugs often create inconsistencies in the internal data of a running program. Programs can be written to check the consistency of their own internal data while running. If an inconsistency is encountered, the program can immediately halt, so that the bug can be located and fixed. Alternatively, the program can simply inform the user, attempt to correct the inconsistency, and continue running.

Development methodologies 

There are several schemes for managing programmer activity, so that fewer bugs are produced. Many of these fall under the discipline of software engineering (which addresses software design issues as well.) For example, formal program specifications are used to state the exact behavior of programs, so that design bugs can be eliminated.

Programming language support 

Programming languages often include features which help programmers deal with bugs, such as exception handling. In addition, many recently-invented languages have deliberately excluded features which can easily lead to bugs. For example, the Java programming language does not support pointer arithmetic.

Wikipedia does not yet have an article with this exact name. ... Programming style (also called coding standards or code convention) is a term that describes conventions for writing source code in a certain programming language. ... Wikipedia does not yet have an article with this exact name. ... In computer science control flow (or alternatively, flow of control) refers to the order in which the individual statements or instructions of an imperative program are performed or executed. ... Software engineering (SE) is the design, development, and documentation of software by applying technologies and practices from computer science, project management, engineering, application domains, interface design, digital asset management and other fields. ... A program specification is the definition of what a computer program is expected to do. ... A programming language is an artificial language that can be used to control the behavior of a machine, particularly a computer. ... Exception handling is a programming language construct or computer hardware mechanism designed to handle the occurrence of some condition that changes the normal flow of execution. ... Java is an object-oriented programming language developed by Sun Microsystems in the early 1990s. ... It has been suggested that Software pointer be merged into this article or section. ...

Debugging

The typical bug history (GNU Classpath project data). A bug, submitted by the user, is unconfirmed. A reproduced bug is a confirmed bug. The confirmed bugs are later fixed. Bugs, belonging to other categories (unreproducible, will not be fixed, etc) are usually in the minority

Main article: Debugging

Finding and fixing bugs, or "debugging", has always been a major part of computer programming. Maurice Wilkes, an early computing pioneer, described his realization in the late 1940s that much of the rest of his life would be spent finding mistakes in his own programs. As computer programs grow more complex, bugs become more common and difficult to fix. Often programmers spend more time and effort finding and fixing bugs than writing new code. Image File history File links Classpath_bugs. ... Image File history File links Classpath_bugs. ... Demonstration of the GNU Classpath Swing GNU Classpath is a project aiming to create a free implementation of the standard class library for the Java programming language. ... Debugging is a methodical process of finding and reducing the number of bugs, or defects, in a computer program or a piece of electronic hardware thus making it behave as expected. ... Programming redirects here. ... Maurice V. Wilkes Maurice Vincent Wilkes (born June 26, 1913 in Dudley, Staffordshire, England) is a British computer scientist, credited with several important developments in computing. ... The 1940s decade ran from 1940 to 1949. ...

Usually, the most difficult part of debugging is locating the erroneous part of the source code. Once the mistake is found, correcting it is usually easy. Programs known as debuggers exist to help programmers locate bugs. However, even with the aid of a debugger, locating bugs is something of an art. Source code (commonly just source or code) is any series of statements written in some human-readable computer programming language. ... Debug redirects here. ...

Typically, the first step in locating a bug is finding a way to reproduce it easily. Once the bug is reproduced, the programmer can use a debugger or some other tool to monitor the execution of the program in the faulty region, and find the point at which the program went astray. Sometimes, a bug is not a single flawed instruction, but represents an error of thinking or planning on the part of the programmer. Such logic errors require a section of the program to be overhauled or rewritten. With a runtime error the program begins running, but then crashes or gets stuck pursuing a never ending calculation. ...

It is not always easy to reproduce bugs. Some bugs are triggered by inputs to the program which may be difficult for the programmer to re-create. One cause of the Therac-25 radiation machine deaths was a bug that occurred only when the machine operator very rapidly entered a treatment plan; it took days of practice to become able to do this, so the bug did not manifest in testing or when the manufacturer attempted to duplicate it. Other bugs may disappear when the program is run with a debugger; these are heisenbugs (humorously named after the Heisenberg uncertainty principle.) Therac-25 was a radiation therapy machine produced by Atomic Energy of Canada Limited. ... Heisenbug is a term used in software programming to describe a computer bug that disappears or alters its characteristics when it is researched. ... In quantum physics, the Heisenberg uncertainty principle is a mathematical limit on the accuracy with which it is possible to measure everything there is to know about a physical system. ...

Debugging is still a tedious task requiring considerable manpower. Since the 1990s, particularly following the Ariane 5 Flight 501 disaster, there has been a renewed interest in the development of effective automated aids to debugging. For instance, methods of static code analysis by abstract interpretation have already made significant achievements, while still remaining much of a work in progress. For the band, see 1990s (band). ... Flight 501, which took place on on June 4, 1996, was the first test flight of the Ariane 5 expendable launch system. ... Static analysis is the term applied to the analysis of computer software that is performed without actually executing programs built from that software (analysis performed on executing programs is known as dynamic analysis). ... In computer science, abstract interpretation is a theory of sound approximation of the semantics of computer programs, based on monotonic functions over ordered sets, especially lattices. ...

Famous computer bugs

Space exploration

• NASA Mariner 1 went off-course during launch, due to a missing 'bar' in its FORTRAN software (July 22, 1962).[7]
• NASA Apollo 11 landing problem (July 20, 1969).
• NASA Voyager 2 (January 25, 1986).
• Phobos 1 lost (September 10, 1988).
• ESA Ariane 5 Flight 501 self-destruction 40 seconds after takeoff (June 4, 1996).
• NASA Mars Climate Orbiter destroyed due to incorrect orbit insertion (September 23, 1999).
• Mars Polar Lander lost (December 3, 1999).
• NASA Mars Rover freezes due to too many open files in flash memory (January 21, 2004).

Astronaut Buzz Aldrin on the surface of the Moon. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States Government, responsible for that nations public space program. ... Launch of Mariner 1 Mariner 1 was the first spacecraft of the Mariner program. ... Fortran (previously FORTRAN[1]) is a general-purpose[2], procedural,[3] imperative programming language that is especially suited to numeric computation and scientific computing. ... July 22 is the 203rd day (204th in leap years) of the year in the Gregorian Calendar, with 162 days remaining. ... 1962 (MCMLXII) was a common year starting on Monday (the link is to a full 1962 calendar). ... The National Aeronautics and Space Administration (NASA) is an agency of the United States Government, responsible for that nations public space program. ... Apollo 11 was the first manned mission to land on the Moon. ... July 20 is the 201st day (202nd in leap years) of the year in the Gregorian Calendar, with 164 days remaining. ... Year 1969 (MCMLXIX) was a common year starting on Wednesday (the link is to a full 1969 calendar). ... The National Aeronautics and Space Administration (NASA) is an agency of the United States Government, responsible for that nations public space program. ... Trajectory Voyager 2 is an unmanned interplanetary spacecraft. ... January 25 is the 25th day of the year in the Gregorian calendar. ... 1986 (MCMLXXXVI) was a common year starting on Wednesday of the Gregorian calendar. ... The Phobos program was an unmanned space mission consisting of two probes launched by the Soviet Union to study Mars and its moons Phobos and Deimos. ... September 10 is the 253rd day of the year (254th in leap years). ... 1988 (MCMLXXXVIII) was a leap year starting on Friday of the Gregorian calendar. ... ESA redirects here. ... Ariane 5 mock-up Ariane 5 is a European expendable launch system designed to deliver satellites into geostationary transfer orbit and to send payloads to Low Earth orbit. ... Flight 501, which took place on on June 4, 1996, was the first test flight of the Ariane 5 expendable launch system. ... June 4 is the 155th day of the year in the Gregorian calendar (156th in leap years), with 210 days remaining. ... 1996 (MCMXCVI) was a leap year starting on Monday of the Gregorian calendar, and was designated the International Year for the Eradication of Poverty. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States Government, responsible for that nations public space program. ... Mars Climate Orbiter during tests The Mars Climate Orbiter (formerly the Mars Surveyor 98 Orbiter) was one of two spacecraft in the Mars Surveyor 98 program, the other being the Mars Polar Lander (formerly the Mars Surveyor 98 Lander). ... September 23 is the 266th day of the year (267th in leap years). ... 1999 (MCMXCIX) was a common year starting on Friday, and was designated the International Year of Older Persons by the United Nations. ... Conceptual drawing of the Mars Polar Lander on the surface of Mars. ... December 3 is the 337th (in leap years the 338th) day of the year in the Gregorian calendar. ... 1999 (MCMXCIX) was a common year starting on Friday, and was designated the International Year of Older Persons by the United Nations. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States Government, responsible for that nations public space program. ... MER-A (Spirit) is the first of the two Mars Exploration Rover Missions. ... January 21 is the 21st day of the year in the Gregorian calendar. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ...

Medical

• The Therac-25 accidents (1985-1987), quite possibly the most serious computer-related failure ever in terms of human life (at least five died).

See drugs, medication, and pharmacology for substances that are used to treat patients. ... Therac-25 was a radiation therapy machine produced by Atomic Energy of Canada Limited. ...

Computing

• The year 2000 problem, popularly known as the "Y2K bug", spawned fears of worldwide economic collapse and an industry of consultants providing last-minute fixes.
• The Pentium FDIV bug.

Originally, the word computing was synonymous with counting and calculating, and a science and technology that deals with the original sense of computing mathematical calculations. ... Y2K redirects here. ... On October 30, 1994, Professor Thomas Nicely who was then at Lynchburg College reported a bug in the Pentium floating point unit. ...

Electric power transmission

• The 2003 North America blackout was triggered by a local outage that went undetected due to a race condition in General Electric Energy's XA/21 monitoring software.

Power line redirects here. ... The 2003 North America blackout was a massive power outage that occurred throughout parts of the northeastern United States and eastern Canada on Thursday, August 14, 2003. ... A race hazard (or race condition) is a flaw in a system or process where the output exhibits unexpected critical dependence on the relative timing of events. ...

Telecommunications

• AT&T long distance network crash (January 15, 1990), documented in Bruce Sterling's The Hacker Crackdown.

Telecommunication involves the transmission of signals over a distance for the purpose of communication. ... AT&T (NYSE: T) is the largest provider of both local and long distance telephone services, wireless service (formerly known as Cingular Wireless), and DSL internet access in the United States. ... January 15 is the 15th day of the year in the Gregorian calendar. ... 1990 (MCMXC) was a common year starting on Monday of the Gregorian calendar. ... Bruce Sterling at the Ars Electronica Festival Michael Bruce Sterling (born April 14, 1954) is an American science fiction author, best known for his novels and his seminal work on the Mirrorshades anthology, which defined the cyberpunk genre. ... The Hacker Crackdown: Law and Disorder on the Electronic Frontier is a book written by science fiction writer Bruce Sterling in 1992. ...

Military

• The MIM-104 Patriot bug, which resulted in the deaths of 28 Americans in Dharan, Saudi Arabia (February 25, 1991).
• Chinook crash on Mull of Kintyre: the cause of this event remains a mystery, but strong suspicions have been raised that software problems were a contributory factor.

Four Patriot missiles like the one shown here can be fired from this mobile launcher between loadings. ... Four Patriot missiles like the one shown here can be fired from this mobile launcher between loadings. ... Road to Dhahran (Picture taken from Khobar way) Dhahran ([[Arabic language الظهران al-Dahrān), or Dharan is a city in Saudi Arabia. ... February 25 is the 56th day of the year in the Gregorian Calendar. ... 1991 (MCMXCI) was a common year starting on Tuesday of the Gregorian calendar. ... At 6pm on 2nd June 1994 the Royal Air Force (RAF) Chinook helicopter designated ZD 576 crashed into a hill on the Mull of Kintyre. ...

Computer and video games

• The Missingno. and Glitch City bugs, found in the Pokémon series
• The Minus world in NES version of Super Mario Brothers

It has been suggested that Multiplayer game be merged into this article or section. ... It has been suggested that M be merged into this article or section. ... Screenshot of the Glitch City accessed through the Cinnabar Coast (the moment that the player comes out of the Safari Building) Glitch City is a term used by Pokémon gamers to refer to a hidden fictional city caused by a bug that occurs in the Pokémon video game... The official Pokémon logo. ... Super Mario Bros. ... NES redirects here. ... Super Mario Bros. ...

Modern bugs and security holes

While people would like bugs to be fixed before a new release, it is common practice for software to be released with known, but considered non-critical, bugs. While software products contain an unknown number of unknown bugs when shipped, measurements during the testing may provide a statistically reliable estimate of the number of likely bugs remaining.

Security vulnerabilities

Also known as security holes. Many computer systems are able to be infected by viruses. Viruses exploit known vulnerabilities in the system - which may or may not be bugs. Viruses are not bugs in themselves - they are typically programs that are doing precisely what they were designed to do. However, viruses are occasionally referred to as such in the popular press.

Although all operating systems are vulnerable to viruses, most virus writers only target (write viruses for) operating systems with large userbases, such as various Windows versions, so as to maximize the virus distribution and damages caused by the virus. Microsoft Windows is the name of several families of proprietary software operating systems by Microsoft. ...

Common types of computer bugs

• Divide by zero
• Infinite loops
• Arithmetic overflow or underflow
• Exceeding array bounds
• Using an uninitialized variable
• Accessing memory not owned (Access violation)
• Memory leak or Handle leak
• Stack overflow or underflow
• Buffer overflow
• Deadlock
• Off by one error
• Race hazard
• Loss of precision in type conversion

In mathematics, a division is called a division by zero if the divisor is zero. ... An infinite loop is a sequence of instructions in a computer program which loops endlessly. ... The term arithmetic overflow or simply overflow has the following meanings. ... The term arithmetic underflow or simply underflow has the following meanings. ... In computer programming, a group of homogeneous elements of a specific data type is known as an array, one of the simplest data structures. ... In computing, an uninitialized variable is a variable that is declared but is not set to a definite known value before it is used. ... An access violation is the attempt by a computer process to access a memory area that it does not own or have permission to access. ... In computer science, a memory leak is a particular kind of unintentional memory consumption by a computer program where the program fails to release memory when no longer needed. ... Handle leak is term used in software engineering to descibe a particular kind of programming bug. ... Simple representation of a stack In computer science, a stack is a temporary abstract data type and data structure based on the principle of Last In First Out (LIFO). ... In computer security and programming, a buffer overflow, or buffer overrun, is a programming error which may result in a memory access exception and program termination, or in the event of the user being malicious, a breach of system security. ... It has been suggested that Circular wait be merged into this article or section. ... An off-by-one error in computer programming is an avoidable error in which a loop iterates one too many or one too few times than desired. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In computer science, type conversion or typecasting refers to changing an entity of one data type into another. ...

See also

• Glitch
• ISO 9126, which classifies a bug as either a defect or a nonconformity
• Workaround
• Bug tracker
• Bit rot
• Anti-pattern
• Unusual software bugs (Schroedinbug, Heisenbug, Bohr bug, and Mandelbug)

Glitch City, a Pokémon programming error that creates a jumble of pixels. ... ISO 9126 is an international standard for the evaluation of software. ... A workaround is a bypass of a recognized problem in a system. ... A bugtracker is a ticket tracking system that is designed especially to manage problems (software bugs) with computer programs. ... Bit rot is a colloquial computing term used either to describe gradual decay of storage media or to facetiously describe the spontaneous degradation of a software program over time. ... Anti-patterns, also referred to as pitfalls, are classes of commonly-reinvented bad solutions to problems. ... Unusual software bugs are a class of software bugs that are considered exceptionally difficult to understand and repair. ...

Notes

1. ^ Edison to Puskas, 13 November 1878, Edison papers, Edison National Laboratory, U.S. National Park Service, West Orange, N.J., cited in Thomas P. Hughes, American Genesis: A History of the American Genius for Invention, Penguin Books, 1989, ISBN 0-14-009741-4, on page 75.
2. ^ Danis, Sharron Ann: "Rear Admiral Grace Murray Hopper"[1]
3. ^ IEEE Annals of the History of Computing, Vol 22 Issue 1, 2000

November 13 is the 317th day of the year (318th in leap years) in the Gregorian Calendar, with 48 days remaining. ... 1878 (MDCCCLXXVIII) was a common year starting on Tuesday (see link for calendar). ...

External links

• Collection of Software Bugs (Thomas Huckle, TU München)
• Computer-Related Incidents with Commercial Aircraft (Peter B. Ladkin et al., Universität Bielefeld)
• An Investigation of the Therac-25 Accidents (Nancy Leveson, University of Washington and Clark S. Turner, University of California at Irvine)
• Fatal Dose: Radiation Deaths linked to AECL Computer Errors (Barbara Wade Rose, Canadian Coalition for Nuclear Responsibility)
• Software Horror Stories (Nachum Dershowitz)
• Software Does Not Fail (Paul Niquette]
• Picture of the "first computer bug" The error of this term is elaborated above. (Naval Historical Center)
• Page from 1947 log book with "first actual case of bug being found" (moth) (National Museum of American History)
• The First Computer Bug! An email from 1981 about Adm. Hopper's bug
• How to Report Bugs Effectively (Simon G. Tatham)
• Rates of Design Failure
• Bug Tracking Basics: A beginner’s guide to reporting and tracking defects (Mitch Allen)
• History's Worst Software Bugs
• Bug Isolation Project - This project is to track bugs of popular open source software. Everyone can participate if he/she has Fedora Core 5 installed.