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Cognitive ergonomics[edit]

Main article: Cognitive ergonomics

Cognitive ergonomics is concerned with mental processes, such as perception, memory, reasoning, and motor response, as they affect interactions among humans and other elements of a system.[5] (Relevant topics include mental workload, decision-making, skilled performance, human reliability, work stress and training as these may relate to human-system and Human-Computer Interaction design.)

Organizational ergonomics[edit]

Organizational ergonomics is concerned with the optimization of socio-technical systems, including their organizational structures, policies, and processes.[5] (Relevant topics include communication, crew resource management, work design, work systems, design of working times, teamwork, participatory design, community ergonomics, cooperative work, new work programs, virtual organizations, telework, and quality management.)

Two thirds of employees in industrialized countries use a computer on a daily basis. One in five interact with a computer at least 3/4 of the total work-time1. This usage of the technology ushered in an epidemic of work related ailments known as musculoskeletal disorders (MSDs). They are also known as repetitive motion disorder (RMD), repetitive motion injury (RMI), repetitive strain injury (RSI), ergonomic related disorder (ERD) and cumulative trauma disorder (CTD).

Though these disorders may as yet not be household terms, the patent effects of substantial computer use reveal themselves in terms of increased morbidity and declining productivity. In short, in the absence of ergonomic practices, employee efficiency in the American workplace takes a substantial hit.

Digital connections
‘Technology is connecting us in ways never seen before in human history. How will that change our societies, our relationships, ourselves?’

That’s the question that interests Michael Wesch. The last time communications technology had such a wide-ranging impact was 500 years ago with the invention of the printing press. Being able to print texts instead of writing them by hand transformed the world. It changed the way people could communicate with each other. Suddenly, multiple copies of books could be made quickly and easily. As more books became available, so ideas spread much more rapidly. But what will be the impact of digital technology, which is the most powerful connecting tool we have ever seen?

Michael Wesch argues that communication is fundamental to our relationships and so it follows that a change in the way we communicate will change those relationships. Wesch, a university professor, explores digital communication in his work. In particular, Wesch and his students look at social networking and other interactive internet tools. A well-known example of such an application is YouTube. When people create and share personal videos on YouTube, anyone anywhere can watch it. Wesch says that this leads to some people feeling a sort of deep connection with the entire world. But it’s not a real relationship – it’s not the same as the connection you feel with a member of your family. In fact, as Wesch says, it’s a relationship without any real responsibility which you can turn off at any moment. So does it make sense to talk about a YouTube ‘community’?

Wesch himself experienced the impact of digital media when he created and posted his own short video on YouTube. It attracted immediate attention and has been viewed millions of times. In his video he tells us that webpages get 100 billion hits a day and that a new blog is started every half second. He asks us to think about the power of this technology and how we use it. What could we do with it? What is its potential?

Wesch isn’t interested in what new media was originally designed for but in how it can be used in other ways. For example, he describes how people organise social protests such as gathering signatures for online petitions via Facebook. He says that he tries to make sure his students end up in control of the technology, not vice versa.

Outside of university, in the real world, Wesch believes it’s crucial for people to be able to operate in the new environment of digital media and to use it for the greatest possible impact. ‘It’s the tragedy of our times that we are now so connected we fail to see it. I want to believe that technology can help us see relationships and global connections in positive new ways. It’s pretty amazing that I have this little box sitting on my desk through which I can talk to any one of a billion people. And yet do any of us really use it for all the potential that’s there?’

Information security
Information security is the process of protecting the availability, privacy, and integrity of data. While the term often describes measures and methods of increasing computer security, it also refers to the protection of any type of important data, such as personal diaries or the classified plot details of an upcoming book. No security system is foolproof, but taking basic and practical steps to protect data is critical for good information security.

Password Protection

Using passwords is one of the most basic methods of improving information security. This measure reduces the number of people who have easy access to the information, since only those with approved codes can reach it. Unfortunately, passwords are not foolproof, and hacking programs can run through millions of possible codes in just seconds. Passwords can also be breached through carelessness, such as by leaving a public computer logged into an account or using a too simple code, like "password" or "1234."

To make access as secure as possible, users should create passwords that use a mix of upper and lowercase letters, numbers, and symbols, and avoid easily guessed combinations such as birthdays or family names. People should not write down passwords on papers left near the computer, and should use different passwords for each account. For better security, a computer user may want to consider switching to a new password every few months.

Antivirus and Malware Protection

One way that hackers gain access to secure information is through malware, which includes computer viruses, spyware, worms, and other programs. These pieces of code are installed on computers to steal information, limit usability, record user actions, or destroy data. Using strong antivirus software is one of the best ways of improvinginformation security. Antivirus programs scan the system to check for any known malicious software, and most will warn the user if he or she is on a webpage that contains a potential virus. Most programs will also perform a scan of the entire system on command, identifying and destroying any harmful objects.

Most operating systems include a basic antivirus program that will help protect the computer to some degree. The most secure programs are typically those available for a monthly subscription or one-time fee, and which can be downloaded online or purchased in a store. Antivirus software can also be downloaded for free online, although these programs may offer fewer features and less protection than paid versions.

Even the best antivirus programs usually need to be updated regularly to keep up with the new malware, and most software will alert the user when a new update is available for downloading. Users must be aware of the name and contact method of each anti-virus program they own, however, as some viruses will pose as security programs in order to get an unsuspecting user to download and install more malware. Running a full computer scan on a weekly basis is a good way to weed out potentially malicious programs.


A firewall helps maintain computer information security by preventing unauthorized access to a network. There are several ways to do this, including by limiting the types of data allowed in and out of the network, re-routing network information through a proxyserver to hide the real address of the computer, or by monitoring the characteristics of the data to determine if it's trustworthy. In essence, firewalls filter the information that passes through them, only allowing authorized content in. Specific websites, protocols (like File Transfer Protocol or FTP), and even words can be blocked from coming in, as can outside access to computers within the firewall.

Most computer operating systems include a pre-installed firewall program, but independent programs can also be purchased for additional security options. Together with an antivirus package, firewalls significantly increase information security by reducing the chance that a hacker will gain access to private data. Without a firewall, secure data is more vulnerable to attack.

Codes and Cyphers

Encoding data is one of the oldest ways of securing written information. Governments and military organizations often use encryption systems to ensure that secret messages will be unreadable if they are intercepted by the wrong person. Encryption methods can include simple substitution codes, like switching each letter for a corresponding number, or more complex systems that require complicated algorithms for decryption. As long as the code method is kept secret, encryption can be a good basic method of information security.

On computers systems, there are a number of ways to encrypt data to make it more secure. With a symmetric key system, only the sender and the receiver have the code that allows the data to be read. Public or asymmetric key encryption involves using two keys — one that is publicly available so that anyone can encrypt data with it, and one that is private, so only the person with that key can read the data that has been encoded. Secure socket layers use digital certificates, which confirm that the connected computers are who they say they are, and both symmetric and asymmetric keys to encrypt the information being passed between computers.

Legal Liability

Businesses and industries can also maintain information security by using privacy laws. Workers at a company that handles secure data may be required to sign non-disclosure agreements (NDAs), which forbid them from revealing or discussing any classified topics. If an employee attempts to give or sell secrets to a competitor or other unapproved source, the company can use the NDA as grounds for legal proceedings. The use of liability laws can help companies preserve their trademarks, internal processes, and research with some degree of reliability.

Training and Common Sense

One of the greatest dangers to computer data security is human error or ignorance. Those responsible for using or running a computer network must be carefully trained in order to avoid accidentally opening the system to hackers. In the workplace, creating a training program that includes information on existing security measures as well as permitted and prohibited computer usage can reduce breaches in internal security. Family members on a home network should be taught about running virus scans, identifying potential Internet threats, and protecting personal information online.

In business and personal behavior, the importance of maintaining information securitythrough caution and common sense cannot be understated. A person who gives out personal information, such as a home address or telephone number, without considering the consequences may quickly find himself the victim of scams, spam, and identity theft. Likewise, a business that doesn't establish a strong chain of command for keeping data secure, or provides inadequate security training for workers, creates an unstable security system. By taking the time to ensure that data is handed out carefully and to reputable sources, the risk of a security breach can be significantly reduced.
Information security

Cyber terrorists are a fearsome lot, more dangerous every day. As companies try to buttress their security walls, they're falling short of professionals.

Recently, the number of internet-based security attacks have mounted dangerously. According to CERT/CC, the internet security research centre at Carnegie Mellon University, USA, the number of security incidents reported have increased to an alarming 137,529 in '03 — compared to 82,094 in '02 and a mere 1,334 a decade ago.

Despite its importance, businesses across the world have paid only lip service to information security. Until recently, companies, especially in developing countries like India, made no allowance in their budget forinformation security and did not consider it as mission critical. However, a recent spate of security intrusions, malicious software such as viruses and denial of service attacks on corporate websites, like the recent ones on Microsoft and SCO by MyDoom, have changed the mind set of Indian businesses.

As organisations continue to deploy mission critical network centric information systems, managing the security of such systems has become critical. For example, a recent Economic Times-CIO survey reported that organisations spend up to 16.7% of their budget on information security, next only to their spending on enterprise systems.

Companies like Mahindra & Mahindra and ICICI have full-fledged teams working on deployment and maintenance of information security infrastructure. Not just businesses, governments too are concerned about information security. The US federal government retains more than 10,000 employees classified as computer security professionals, far more than the number present two years ago, to manage its security infrastructure. Of late, even the business process outsourcing (BPO) industry in India has begun to look at information security to protect and ensure data privacy.

Nowadays, we cannot imagine our life without computers and the fact is that they have become so important that nothing can replace them. They seem to be everywhere today. Since 1948 when the first real computer has been invented our life has changed so much that we can call it real digital revolution.

First computers differed from today's ones. They were so huge that they occupied whole rooms or buildings being relatively slow. They were not faster than modern simple watches or calculators. Nowadays they are also used by scientist and they may also be as huge as the old ones but they are millions times faster. They can perform many complex operations simultaneously and scientist practically can't do without them. Thanks to them people has access to enormous amount of information. Gathering data has never been more simple than now. They are not only used in laboratories but also in factories to control production. Sometimes it is computers who manufacture other computers.

But not only in science and industry computers are being used. Thanks to them modern medicine can diagnose diseases faster and more thoroughly. Also in banking system computers have become irreplaceable. They control ATMs, all data is stored on special hard disks and paper isn't used in accountancy any more. Furthermore, architects, designers and engineers can't imagine their work without computers. This machines are really everywhere and we depend on them also in such fields as criminology. They help police to solve crimes and collect evidence.

Moreover, computers are wide-spread in education. Except their classic tasks such as administration and accountancy they are used in process of learning. Firstly, they store enormous amount of data which helps students to gain an information. Secondly, thanks to special teaching techniques and programs they improve ours skills of concentration and assimilation of knowledge. They have become so popular that not knowing how to use them means to be illiterate.

Of course except this superb features there is also dark side of computer technology because every invention brings us not only benefits but also threats.


1. Computers saves storage place. Imagine how much paper would have to be used, how many trees would have to be cut just to store information which is today on hard disks. Data stored on just one CD in paper form would use room of dozens square meters and would weight thousands of kilos. Nowadays techniques of converting data from paper to digital form has also tremendously developed. You can simply rewrite the text using a keyboard. If you are not good at it you can use a scanner to scan necessary documents. At least there are special devices which can transfer our voice into text. Thanks to computers banks, private and government companies, libraries, and many other institutions can save millions of square meters and billions of dollars. Nowadays we have access to billions of information and due to the computer's capabilities we actually don't need to worry not only how to store them but also how to process them.

2. Computers can calculate and process information faster and more accurate than human. Sometimes there are false information in newspapers that due to the computer's mistake something has failed. But it's not truth because machines cannot make mistakes by it's own. Sometimes it's short circuit, other time it's hardware problem but most often it is human mistake, someone who designed and wrote the flawed computer program.

3. Computers improve our lives. They are very useful in office work, we can write text such as reports and analysis. Compared with old typewriters when using computers we don't have to worry about making mistakes in typewriting because special programs helps as to avoid them and we can change them any time. When the text is finished we can print it in as many copies as we want. At least but not at last, we can communicate with whole world very fast and cheap using Internet.

4. Computers are user-friendly. We can watch videos and listen to the music having only PC. We don't need video player, TV and stacking hi-fi any more. Furthermore, we don't have to buy PC's which can take much room due to their other necessary components and wires. We can always buy laptop or palm top which is even smaller, and use them outside anywhere we want.


1. Computers are dangerous to our health. The monitors used to be dangerous for our eyesight. Nowadays due to technological development they are very safe. But there are other threats to our health than damaging our sight. Working with computers and permanent looking on the monitor can cause epilepsy, especially with children. Very often parents want to have a rest and don't draw enough attention to how long their children use computer. This negative effects also concerns TV screen.

2. Computers sometimes brake down. The biggest problem is when our hard disk brakes down because of the data stored on it. Other hardware is easily replaceable. But there are many ways of avoiding consequences of loosing our data, for example by saving it on CDs. Except hardware failures there are also software ones. For example, for many years Windows Operating System was very unstable and that's why many other OS were written. Now the most common are Linux, Windows XP, MacOs (for Macintosh computers). Except of unstable OS another and maybe the main threat to our data are computer viruses. There are billions of them and every day new ones come into being. If you have the Internet connection you have to be particularly careful and download anti-virus programs. Fortunately, there are also many of them and most of them are freeware. You have to remember to download updates.

3. Violence and sex. The main threat to younger users of computers are internet pornography and bloody games. The presence of sexual content or level of violence should be properly marked and parents are obliged to draw their attention to this issue. There are many extremely bloody games such as "grand theft auto", "quake" etc. For example, in GTA you are a member of mafia and to promote in crime hierarchy you should kidnap people, steal cars, robe banks etc. As a bonus you can also run over pedestrians. There are also many games in which you are a soldier and your mission is to kill as many enemies as possible. The other threat to our children is internet pornography. The availability of sexual content is enormous and you can do practically nothing to protect your child, especially when it's interested in this matter.

4. The other threat is that you can be a computer addict. If you spend most of your free time using computer you should go to see a psychologist.

However, I think that the situation is very serious. Computers are practically irreplaceable and we can't make without them any more. They are everywhere, at our homes, schools, at work, in our cars. It is very possible that the next stage of human evolution is some kind of superb half human and half machines. On the other hand I don't think it is the closest future. But the truth is that that computers will rule the world sooner or later.

Algorithms and Applications
Humans perceive the three-dimensional structure of the world with apparent ease. However, despite all of the recent advances in computer vision research, the dream of having a computer interpret an image at the same level as a two-year old remains elusive. Why is computer vision such a challenging problem and what is the current state of the art?

Computer Vision: Algorithms and Applications explores the variety of techniques commonly used to analyze and interpret images. It also describes challenging real-world applications where vision is being successfully used, both for specialized applications such as medical imaging, and for fun, consumer-level tasks such as image editing and stitching, which students can apply to their own personal photos and videos.

More than just a source of “recipes,” this exceptionally authoritative and comprehensive textbook/reference also takes a scientific approach to basic vision problems, formulating physical models of the imaging process before inverting them to produce descriptions of a scene. These problems are also analyzed using statistical models and solved using rigorous engineering techniques

Topics and features: structured to support active curricula and project-oriented courses, with tips in the Introduction for using the book in a variety of customized courses; presents exercises at the end of each chapter with a heavy emphasis on testing algorithms and containing numerous suggestions for small mid-term projects; provides additional material and more detailed mathematical topics in the Appendices, which cover linear algebra, numerical techniques, and Bayesian estimation theory; suggests additional reading at the end of each chapter, including the latest research in each sub-field, in addition to a full Bibliography at the end of the book; supplies supplementary course material for students at the associated website, http://szeliski.org/Book/.

Suitable for an upper-level undergraduate or graduate-level course in computer science or engineering, this textbook focuses on basic techniques that work under real-world conditions and encourages students to push their creative boundaries. Its design and exposition also make it eminently suitable as a unique reference to the fundamental techniques and current research literature in computer vision.

Retrospective: An Axiomatic Basis for Computer Programming

By C.A.R. Hoare 
Communications of the ACM, Vol. 52 No. 10, Pages 30-32

Retrospective (1969–1999)

My first job (1960–1968) was in the computer industry; and my first major project was to lead a team that implemented an early compiler for ALGOL 60. Our compiler was directly structured on the syntax of the language, so elegantly and so rigorously formalized as a context-free language. But the semantics of the language was even more important, and that was left informal in the language definition. It occurred to me that an elegant formalization might consist of a collection of axioms, similar to those introduced by Euclid to formalize the science of land measurement. My hope was to find axioms that would be strong enough to enable programmers to discharge their responsibility to write correct and efficient programs. Yet I wanted them to be weak enough to permit a variety of efficient implementation strategies, suited to the particular characteristics of the widely varying hardware architectures prevalent at the time.

I expected that research into the axiomatic method would occupy me for my entire working life; and I expected that its results would not find widespread practical application in industry until after I reached retirement age. These expectations led me in 1968 to move from an industrial to an academic career. And when I retired in 1999, both the positive and the negative expectations had been entirely fulfilled.

The main attraction of the axiomatic method was its potential provision of an objective criterion of the quality of a programming language, and the ease with which programmers could use it. For this reason, I appealed to academic researchers engaged in programming language design to help me in the research. The latest response comes from hardware designers, who are using axioms in anger (and for the same reasons as given above) to define the properties of modern multicore chips with weak memory consistency.

One thing I got spectacularly wrong. I could see that programs were getting larger, and I thought that testing would be an increasingly ineffective way of removing errors from them. I did not realize that the success of tests is that they test the programmer, not the program. Rigorous testing regimes rapidly persuade error-prone programmers (like me) to remove themselves from the profession. Failure in test immediately punishes any lapse in programming concentration, and (just as important) the failure count enables implementers to resist management pressure for premature delivery of unreliable code. The experience, judgment, and intuition of programmers who have survived the rigors of testing are what make programs of the present day useful, efficient, and (nearly) correct. Formal methods for achieving correctness must support the intuitive judgment of programmers, not replace it.

My basic mistake was to set up proof in opposition to testing, where in fact both of them are valuable and mutually supportive ways of accumulating evidence of the correctness and serviceability of programs. As in other branches of engineering, it is the responsibility of the individual software engineer to use all available and practicable methods, in a combination adapted to the needs of a particular project, product, client, or environment. The best contribution of the scientific researcher is to extend and improve the methods available to the engineer, and to provide convincing evidence of their range of applicability. Any more direct advocacy of personal research results actually excites resistance from the engineer.

Progress (1999–2009)

On retirement from University, I accepted a job offer from Microsoft Research in Cambridge (England). I was surprised to discover that assertions, sprinkled more or less liberally in the program text, were used in development practice, not to prove correctness of programs, but rather to help detect and diagnose programming errors. They are evaluated at runtime during overnight tests, and indicate the occurrence of any error as close as possible to the place in the program where it actually occurred. The more expensive assertions were removed from customer code before delivery. More recently, the use of assertions as contracts between one module of program and another has been incorporated in Microsoft implementations of standard programming languages. This is just one example of the use of formal methods in debugging, long before it becomes possible to use them in proof of correctness.

I did not realize that the success of tests is that they test the programmer, not the program.
In 1969, my proof rules for programs were devised to extract easily from a well-asserted program the mathematical 'verification conditions', the proof of which is required to establish program correctness. I expected that these conditions would be proved by the reasoning methods of standard logic, on the basis of standard axioms and theories of discrete mathematics. What has happened in recent years is exactly the opposite of this, and even more interesting. New branches of applied discrete mathematics have been developed to formalize the programming concepts that have been introduced since 1969 into standard programming languages (for example, objects, classes, heaps, pointers). New forms of algebra have been discovered for application to distributed, concurrent, and communicating processes. New forms of modal logic and abstract domains, with carefully restricted expressive power, have been invented to simplify human and mechanical reasoning about programs. They include the dynamic logic of actions, temporal logic, linear logic, and separation logic. Some of these theories are now being reused in the study of computational biology, genetics, and sociology.

Equally spectacular (and to me unexpected) progress has been made in the automation of logical and mathematical proof. Part of this is due to Moore's Law. Since 1969, we have seen steady exponential improvements in computer capacity, speed, and cost, from megabytes to gigabytes, and from megahertz to gigahertz, and from megabucks to kilobucks. There has been also at least a thousand-fold increase in the efficiency of algorithms for proof discovery and counterexample (test case) generation. Crudely multiplying these factors, a trillion-fold improvement has brought us over a tipping point, at which it has become easier (and certainly more reliable) for a researcher in verification to use the available proof tools than not to do so. There is a prospect that the activities of a scientific user community will give back to the tool-builders a wealth of experience, together with realistic experimental and competition material, leading to yet further improvements of the tools.

For many years I used to speculate about the eventual way in which the results of research into verification might reach practical application. A general belief was that some accident or series of accidents involving loss of life, perhaps followed by an expensive suit for damages, would persuade software managers to consider the merits of program verification.

This never happened. When a bug occurred, like the one that crashed the maiden flight of the Ariane V spacecraft in 1996, the first response of the manager was to intensify the test regimes, on the reasonable grounds that if the erroneous code had been exercised on test, it would have been easily corrected before launch. And if the issue ever came to court, the defense of 'state-of-the-art' practice would always prevail. It was clearly a mistake to try to frighten people into changing their ways. Far more effective is the incentive of reduction in cost. A recent report from the U.S. Department of Commerce has suggested that the cost of programming error to the world economy is measured in tens of billions of dollars per year, most of it falling (in small but frequent doses) on the users of software rather than on the producers.

The phenomenon that triggered interest in software verification from the software industry was totally unpredicted and unpredictable. It was the attack of the hacker, leading to an occasional shutdown of worldwide commercial activity, costing an estimated $4 billion on each occasion. A hacker exploits vulnerabilities in code that no reasonable test strategy could ever remove (perhaps by provoking race conditions, or even bringing dead code cunningly to life). The only way to reach these vulnerabilities is by automatic analysis of the text of the program itself. And it is much cheaper, whenever possible, to base the analysis on mathematical proof, rather than to deal individually with a flood of false alarms. In the interests of security and safety, other industries (automobile, electronics, aerospace) are also pioneering the use of formal tools for programming. There is now ample scope for employment of formal methods researchers in applied industrial research.


In 1969, I was afraid industrial research would dispose such vastly superior resources that the academic researcher would be well advised to withdraw from competition and move to a new area of research. But again, I was wrong. Pure academic research and applied industrial research are complementary, and should be pursued concurrently and in collaboration. The goal of industrial research is (and should always be) to pluck the 'low-hanging fruit'; that is, to solve the easiest parts of the most prevalent problems, in the particular circumstances of here and now. But the goal of the pure research scientist is exactly the opposite: it is to construct the most general theories, covering the widest possible range of phenomena, and to seek certainty of knowledge that will endure for future generations. It is to avoid the compromises so essential to engineering, and to seek ideals like accuracy of measurement, purity of materials, and correctness of programs, far beyond the current perceived needs of industry or popularity in the market-place. For this reason, it is only scientific research that can prepare mankind for the unknown unknowns of the forever uncertain future.
The phenomenon that triggered interest in software verification from the software industry was totally unpredicted and unpredictable.
So I believe there is now a better scope than ever for pure research in computer science. The research must be motivated by curiosity about the fundamental principles of computer programming, and the desire to answer the basic questions common to all branches of science: what does this program do; how does it work; why does it work; and what is the evidence for believing the answers to all these questions? We know in principle how to answer them. It is the specifications that describes what a program does; it is assertions and other internal interface contracts between component modules that explain how it works; it is programming language semantics that explains why it works; and it is mathematical and logical proof, nowadays constructed and checked by computer, that ensures mutual consistency of specifications, interfaces, programs, and their implementations.

There are grounds for hope that progress in basic research will be much faster than in the early days. I have already described the vastly broader theories that have been proposed to understand the concepts of modern programming. I have welcomed the enormous increase in the power of automated tools for proof. The remaining opportunity and obligation for the scientist is to conduct convincing experiments, to check whether the tools, and the theories on which they are based, are adequate to cover the vast range of programs, design patterns, languages, and applications of today's computers. Such experiments will often be the rational reengineering of existing realistic applications. Experience gained in the experiments is expected to lead to revisions and improvements in the tools, and in the theories on which the tools were based. Scientific rivalry between experimenters and between tool builders can thereby lead to an exponential growth in the capabilities of the tools and their fitness to purpose. The knowledge and understanding gained in worldwide long-term research will guide the evolution of sophisticated design automation tools for software, to match the design automation tools routinely available to engineers of other disciplines.

The End

No exponential growth can continue forever. I hope progress in verification will not slow down until our programming theories and tools are adequate for all existing applications of computers, and for supporting the continuing stream of innovations that computers make possible in all aspects of modern life. By that time, I hope the phenomenon of programming error will be reduced to insignificance: computer programming will be recognized as the most reliable of engineering disciplines, and computer programs will be considered the most reliable components in any system that includes them.

Even then, verification will not be a panacea. Verification technology can only work against errors that have been accurately specified, with as much accuracy and attention to detail as all other aspects of the programming task. There will always be a limit at which the engineer judges that the cost of such specification is greater than the benefit that could be obtained from it; and that testing will be adequate for the purpose, and cheaper. Finally, verification cannot protect against errors in the specification itself. All these limits can be freely acknowledged by the scientist, with no reduction in enthusiasm for pushing back the limits as far as they will go.
Keyboard symbols

You've seen tons of text symbols on Facebook, Myspace and YouTube. Special characters rose to popularity along with social networking. Most text signs, like ♥ aren't really used in books and references, but are easily recognisable graphemes.

Main reasons why symbols are rising to prominence are that they convey same meaning as words, but in a smaller space and they are well recognised among all internet users across the globe independent of their language, culture or ethnicity. Another reason is that they are often used as building blocks of text pictures to depict different emotions, concepts, images and other stuff (✿◠‿◠) You can type symbols right from your keyboard. I'm going to show you how. Also, if you want to check out all the symbols you have in each of font you got installed on your computer, check out Character Maps. ≧◔◡◔≦

Shortcut technique that works on Desktops and most Laptops running MS Windows. You press Alt and, while holding it, type a code on Num Pad. It's very easy, but not as practical for long-term usage as Shift States. Also, you can type many frequently used symbols with this method, but not all like with Shift States.

Shift states

My Windows keyboard layout with symbolsWant to access symbols really fast from your keyboard? Install my custom keyboard layout. E̲n̲t̲i̲r̲e̲l̲y̲ free. Includes source file, so you can edit it the way you want.

Shift states for Windows symbols

Configure your keyboard layout in Windows so that you can type all additional symbols you want as easy as any other text. Takes about 5-10 minutes to set things up, but you'll be typing like a boss.

Character map

MS Windows Character map

CharMap allows you to view and use all characters and symbols available in all fonts (some examples of fonts are "Arial", "Times New Roman", "Webdings") installed on your computer.

Computer Screens Harder To Understand, Less Persuasive
WASHINGTON  Students who read essays on a computer screen found the text harder to understand, less interesting and less persuasive than students who read the same essay on paper, a new study has found.

Researchers had 131 undergraduate students read two articles that had appeared in Time magazine - some read from the magazine, some read the exact same text after it had been scanned into a computer.

"We were surprised that students found paper texts easier to understand and somewhat more convincing," said P. Karen Murphy, co-author of the study and assistant professor of educational psychology at Ohio State University. "It may be that students need to learn different processing abilities when they are attempting to read computerized text."

Murphy said the results of this preliminary study cast doubt on the assumption that computerized texts are essentially more interesting and, thus, more likely to enhance learning.

"Given that there is such an emphasis on using computers in the classroom, this study gives educators reason to pause and examine the supposed benefits associated with computer use in classrooms," she said. "This study provides a first step toward understanding how computers might influence the learning process."

Murphy conducted the study with Ohio State graduate students Joyce Long, Theresa Holleran and Elizabeth Esterly. They presented their results Aug. 5 in Washington at the annual meeting of the American Psychological Association.

The study involved 64 men and 67 women, all undergraduates at Ohio State. The students read two essays that had appeared in Time, one involving doctor-assisted suicide for terminally ill patients and the other about school integration.

Before they read the essays, the students completed questionnaires analyzing their knowledge and beliefs about the subjects in the texts.

After the readings, the students completed questionnaires that probed their understanding of the essays and also asked them about how persuasive and interesting they thought the essays were.

One-third of the students read the print essays and responded to the questionnaires on paper. One-third read the essays on a computer and then responded to the questionnaire on paper. The final third of participants read the essays on the computer screens and responded to the questionnaire online.

The results showed that students in all three groups increased their knowledge after reading the texts, and the beliefs of students in each group became more closely aligned with the authors.

However, there were important differences, such as the fact that students who read the essays on the computer screen found the texts more difficult to understand. This was true regardless of how much computer experience the students reported.

"In some ways, this is surprising because the computerized essays were the exact same text, presenting the exact same information," Murphy said. The computerized texts even included the small picture that appeared in the print edition.

"There is no reason they should be harder to understand. But we think readers develop strategies about how to remember and comprehend printed texts, but these students were unable to transfer those strategies to computerized texts."

The students found the computerized texts less interesting than printed text, which should be expected if they didn't understand the computerized versions as well, she said.

Students who read the essays online also rated the authors as less credible and the arguments as less persuasive. "Again, it may be that if these students did not understand the message, they would not judge the author to be as credible and might not find the arguments as persuasive."

There were no significant differences between the students who read the texts online and responded to the questionnaires on paper, and those who read the online texts and also responded to the questions online.

Murphy said that if the college students in this study had difficulty understanding computerized text, such text may present additional hurdles for less competent readers.

"We shouldn't make it more difficult for children to learn, which is why we need to be careful about how we use computers in the classroom," she said.

"A lot of questions have to be answered before we continue further into making computers part of the curriculum."

Story Source:

The above post is reprinted from materials provided by Ohio State University. 

Computer operations.
Much of the processing computers can be divided into two general types of operation. Arithmetic procedures. Early computers performed mostly arithmetic operations, which gave the false impression that only engineers and scientists could benefit from computers .Of equal importance is the computers operations are computations with numbers such as addition, subtraction, and other mathematical ability to compare two values to determine if one is larger than, smaller than, or equal to the other. This is called a logical operation .The comparison may take place between numbers, letters, sounds, or even drawings The processingofthe computer is based on the computer’sability to perform logical and arithmetical operations.

Instructions must be given to the computer to tell it how to process the data it receives and the format needed for output and storage. The ability to follow the program sets computers apart from most tools. However, new tools ranging from typewriters to microwave ovens have embedded computers, or build-in computers .An embedded computer can accept data to use several options in it’s program, but the program itself cannot be changed. This makes these devices flexible and convenient but not the embedded computers itself.

Curation by Algorithm
Tarleton Gillespie Social media and content-sharing platforms must regularly make decisions about what can be said and done on their sites, extending centuries-old debates about the proper boundaries of public expression into the digital era. But, in addition, the particular ways in which these sites enforce these choices have their own consequences. While some providers depend on editorially managing content, or lean on their user community to govern for them, some are beginning to employ algorithmic means of managing their archive, so offending content can be procedurally and automatically removed, or kept from some users and not others. Curation by algorithm raises new questions about what judgments are being made, whose values are being inscribed into the technical infrastructure, and what a dependence on these tools might mean for the contours of public discourse and users' participation in it.

4. Texts for physics in english for high school

  1. Physical quantities and measurements


physical quantity (or "physical magnitude") is a physical property of a phenomenon, body, or substance, that can be quantified bymeasurement.[1] A physical quantity can be expressed as the combination of a number – usually a real number – and a unit or combination of units; for example, 1.6749275×10−27 kg (the mass of the neutron), or 299792458 metres per second (the speed of light). Physical quantities are measured as 'nu' where n is the number and u is the unit. For example: A boy measured the length of a room as 3m. Here 3 is the number and m(metre) is the unit. 3m can also be written as 300cm. This shows that n1u1 =n2u2. Almost all matters have quantity.

  1. Mechanics


Kinematics is used in astrophysics to describe the motion of celestial bodies and collections of such bodies. In mechanical engineeringrobotics, and biomechanics[7] kinematics is used to describe the motion of systems composed of joined parts (multi-link systems) such as an engine, a robotic arm or the skeleton of the human body.

The use of geometric transformations, also called rigid transformations, to describe the movement of components of a mechanical system simplifies the derivation of its equations of motion, and is central to dynamic analysis.

Kinematic analysis is the process of measuring the kinematic quantities used to describe motion. In engineering, for instance, kinematic analysis may be used to find the range of movement for a given mechanism, and working in reverse, using kinematic synthesis used to design a mechanism for a desired range of motion.[8] In addition, kinematics applies algebraic geometry to the study of the mechanical advantage of a mechanical system or mechanism.


The study of dynamics falls under two categories: linear and rotational. Linear dynamics pertains to objects moving in a line and involves such quantities as forcemass/inertia,displacement (in units of distance), velocity (distance per unit time), acceleration (distance per unit of time squared) and momentum (mass times unit of velocity). Rotational dynamics pertains to objects that are rotating or moving in a curved path and involves such quantities as torquemoment of inertia/rotational inertiaangular displacement (in radians or less often, degrees), angular velocity (radians per unit time), angular acceleration (radians per unit of time squared) and angular momentum (moment of inertia times unit of angular velocity). Very often, objects exhibit linear and rotational motion.

For classical electromagnetism, it is Maxwell's equations that describe the dynamics. And the dynamics of classical systems involving both mechanics and electromagnetism are described by the combination of Newton's laws, Maxwell's equations, and the Lorentz force.

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