cmpute-z

Why a Computer History Museum?

Humans have been creating tools since before recorded history. For many centuries, most tools served to amplify the power of the human body. We call the period of their greatest flowering the Industrial Revolution.

In the last 150 years we have turned to inventing tools that amplify the human mind, and by doing so we are creating the Information Revolution. At its core, of course, is computing.

In the last 150 years we have turned to inventing tools that amplify the human mind, and by doing so we are creating the Information Revolution. At its core, of course, is computing.

“Computer” was once a job title. Computers were people: men and women sitting at office desks performing calculations by hand, or with mechanical calculators. The work was repetitive, slow, and boring. The results were often unreliable.

In the mid 1800s, the brilliant but irascible Victorian scientist Charles Babbage contemplated an error-filled book of navigation tables and famously exclaimed, “I wish to God these calculations had been executed by steam!” Babbage designed his Difference Engine to calculate without errors, and then, astoundingly, designed the Analytical Engine — a completely programmable computer that we would recognize as such today. Unfortunately he failed to build either of those machines.

Automatic computation would have to wait another hundred years. That time is now.

the father of computer:

Bioraphy and Education
Charles Babbage was born in London Dec. 26, 1791, St. Stephan day, in London. He was son of Benjamin Babbage, a banking partner of the Praeds who owned the Bitton Estate in Teignmouth and Betsy Plumleigh Babbage. It was about 1808 when the Babbage family decided to move into the old Rowdens house, located in East Teignmouth, and Benjamin Babbage became a warden of the nearby church of St. Michael.

The father of Charles was a rich man, so it was possible for Charles to receive instruction from several elite schools and teachers during the course of his elementary education. He was about eight when he had to move to a country school to recover from a dangerous fever. His parents sentenced that his "brain was not to be taxed too much"; Babbage wrote: "this great idleness may have led to some of my childish reasonings."
Then, he joined King Edward VI Grammar School in Totnes, South Devon, a thriving comprehensive school that's still operative today, but his fragile health status forced him back to private teaching for a period. Then, he finally joined a 30-student closed number academy managed by Reverend Stephen Freeman. The academy had a big library, where Babbage used to study mathematics by himself, and learned to love it. He had two more personal tutors after leaving the academy. One was a clergyman of Cambridge, and about him Babbage said: "I fear I did not derive from it all the advantages that I might have done.". The other one was an Oxford tutor who teached Babbage the Classics, so that he could be accepted to Cambridge.

Babbage arrived at Trinity College, Cambridge in October 1810. He had a big culture - he knew Lagrange, Leibniz, Lacroix, Simpson... and he was seriously disappointed about the math programs available at Cambridge. So he, with J.Herschel, G.Peacock, and other friends, decided to form the Analytical Society.

When, in 1812, Babbage transferred to Peterhouse, Cambridge, he was the best mathematician; but he failed to graduate with honours.
He received an honorary degree later, without even being examinated, in 1814.

In 1814, Charles Babbage married Georgiana Whitmore at St. Michael's Church in Teignmouth, Devon. His father, for some reason, never gave his approvation. They lived in tranquility at 5 Devonshire Street, Portland Place, London.
Only Three of their 8 children became adult.
Tragically, Charles' father, his wife and one of his sons all died in 1827.
Children
Benjamin Herschel Babbage (1815)

Charles Whitmore Babbage (1817)

Georgiana Whitmore Babbage (1818)

Edward Stewart Babbage (1819)

Francis Moore Babbage (1821)

Dugald Bromheald Babbage (1823)

Henry Prevost Babbage (1824)

Alexander Forbes Babbage (1827)

Timothy grant Babbage (1829)

Design of computers
In Babbage's times there was a really high error rate in the calculation of math tables, when Babbage planned to find a new method that could be use to make it mechanically, removing the human error factor. This idea started to tickle his brain very early, in 1812.
Three different elements influenced him in this decision: he disliked untidiness and unprecision; he was very able with logarithmical tables; he was inspired from an existing work on calculating machines produced by W. Schickard, B.Pascal, and G. Leibniz.
He discussed the main principles of a calculating engine in a letter he wrote to Sir H. Davy in the early 1822.
Difference engine
Babbage presented something that he called "difference engine" to the Royal Astronomical Society on Jun 14, 1822 and in a paper entitled "Note on the application of machinery to the computation of astronomical and mathematical tables."
It was able to calculate polynomials by using a numerical method called the differences method.
The Society approved the idea, and the government granted him £1500 to construct it, in 1823. Charles Babbage converted one of the rooms in his home to a workshop and hired Joseph Clement to oversee construction of the engine. Every part had to be formed by hand using custom machine tools, many of which Babbage himself designed. He took extensive tours of industry to better understand manufacturing processes. Based on these trips and his experience with the difference engine, Babbage published On the Economy of Machinery and Manufacture in 1832. It was the first publication on what we would now call operations research.

The death of Georgiana, Babbage's father, and an infant son interrupted construction in 1827. Work had already taxed Babbage heavily and he was on the edge of a breakdown. John Herschel and several other friends convinced Babbage to take a trip to Europe to recuperate. He passed through the Netherlands, Belgium, Germany, and Italy visiting universities and manufacturing facilities.

In Italy he learned he had been named the Lucasian Professor of Mathematics. He initially wanted to turn down the position but several friends convinced him to accept. He moved to 1 Dorset Street upon returning to England in 1828.

The difference engine project had come under fire during Babbage's absence. Rumours had spread that Babbage had wasted the government's money; that the machine did not work; and that it had no practical value if it did. John Herschel and the Royal Society publicly defended the engine. The government continued its support, advancing £1500 on April 29, 1829, £3000 on December 3, and £3000 on February 24, 1830. Work continued, but Babbage would have continual difficulty getting money from the treasury.

Babbage's problems with the treasury coincided with numerous disagreements with Clement. Babbage had built a two-story, 50 foot long workshop behind his house. It had a glass roof for lighting, and a fireproof, dust-free room to contain the machine. Clement refused to move his operations to the new workshop and demanded more money for the difficulty of travelling across town to oversee construction. In response, Babbage suggested that Clement draw his pay directly from the treasury. Before then, Babbage would get money from the government that he would use to pay Clement. He often had to pay Clement out of his own pocket when the bureaucracy lagged behind Clement's pay schedule. Clement refused the request and stopped working.

Clement further refused to turn over the drawings and tools used to build the difference engine. After an investment of £23000, including £6000 of Babbage's own money, work on the unfinished machine ceased in 1834. Charles wrote, "The drawings and parts of the Engine are at length in a place of safety—I am almost worn out with disgust and annoyance at the whole affair." In 1842 the government officially abandoned the project.
Analytical engine
While he was separated from the difference engine, Babbage began to think about an improved calculating engine. Between 1833 and 1842 he tried to build a machine that would be programmable to do any kind of calculation, not just ones relating to polynomial equations. The first breakthrough came when he redirected the machine's output to the input for further equations. He described this as the machine "eating its own tail". It did not take much longer for him to define the main points of his analytical engine.

The mature analytical engine used punched cards adapted from the Jacquard loom to specify input and the calculations to perform. The engine consisted of two parts: the mill and the store. The mill, analogous to a modern computer's CPU, executed the operations on values retrieved from the store, which we would consider memory. It was the world's first general-purpose computer.

A design for this emerged by 1835. The scale of the work was truly incredible. Babbage and a handful of assistants created 500 large design drawings, 1000 sheets of mechanical notation, and 7000 sheets of scribbles. The completed mill would measure 15 feet tall and 6 feet in diameter. The 100 digit store would stretch to 25 feet long. Babbage constructed only small test parts for his new engine; a full engine was never completed. In 1842, following repeated failures to obtain funding from the First Lord of the Treasury, Babbage approached Sir Robert Peel for funding. Peel refused, and offered Babbage a knighthood instead. Babbage refused. He would continue modifying and improving the design for many years to come.

In October 1842, Federico Luigi, Conte Menabrea, an Italian general and mathematician, published a paper on the analytical engine. Augusta Ada King, Countess of Lovelace, a longtime friend of Babbage, translated the paper into English. Charles suggested that she add notes to accompany the paper. In a series of letters between 1842 and 1843, the pair collaborated on seven notes, the combined length of which was three times longer than the actual paper. In one note Ada prepared a table of execution for a program that Babbage wrote to calculate the Bernoulli numbers. In another, she wrote about a generalized algebra engine that could perform operations on symbols as well as numbers. Lovelace was perhaps the first to grasp the more general goals of Babbage’s machine, and some consider her the world's first computer programmer. She began work on a book describing the analytical engine in more detail, but it was never finished.
Second Difference Engine
Between October 1846 and March 1849 Babbage started designing a second difference engine using knowledge gained from the analytical engine. It used only about 8000 parts, three times fewer than the first. It was a marvel of mechanical engineering.

Unlike the analytical engine that he continually tweaked and modified, he did not try to improve the second difference engine after completing the initial design. Babbage made no attempt to actually construct the machine.

The 24 schematics remained in the Science Museum archives until a full-size replica was built 1985-1991 to celebrate the 200th anniversary of Babbage’s birth. It measured 11 feet long, 7 feet high and 18 inches deep, and weighted 2.6 tonnes. The limits of precision were restricted to those achievable by Babbage.
Babbage's accomplishments
In 1824 Babbage won the Gold Medal of the Royal Astronomical Society "for his invention of an engine for calculating mathematical and astronomical tables".

From 1828 to 1839 Babbage was Lucasian professor of mathematics at Cambridge. He contributed largely to several scientific periodicals, and was instrumental in founding the Astronomical Society in 1820 and the Statistical Society in 1834.

In 1837, responding to the official eight Bridgewater Treatises "On the Power, Wisdom and Goodness of God, as manifested in the Creation", he published his Ninth Bridgewater Treatise putting forward the thesis that God had the omnipotence and foresight to create as a divine legislator, making laws (or programs) which then produced species at the appropriate times, rather than continually interfering with ad hoc miracles each time a new species was required. The book incorporated extracts from correspondence he had been having with John Herschel on the subject.

Charles Babbage also achieved notable results in cryptography. He broke Vigenère's autokey cipher as well as the much weaker cipher that is called Vigenère cipher today. The autokey cipher was generally called "the undecipherable cipher", though owing to popular confusion, many thought that the weaker polyalphabetic cipher was the "undecipherable" one. Babbage's discovery was used to aid English military campaigns, and was not published until several years later; as a result credit for the development was instead given to Friedrich Kasiski, who made the same discovery some years after Babbage.

Babbage also invented the pilot (also called a cow-catcher), the metal frame attached to the front of locomotives that clears the tracks of obstacles in 1838. He also performed several studies on Isambard Kingdom Brunel's Great Western Railway.

He only once endeavoured to enter public life, when, in 1832, he stood unsuccessfully for the borough of Finsbury. He came in last in the polls.
Parts of Babbage's uncompleted mechanisms are available for visits in the London Science Museum. In 1991 a difference engine was completed, starting from Babbage's original plans, and it functioned perfectly.
References and Bibliography

- Passages from the Life of a Philosopher (Charles Babbage).
- Charles Babbage: Pioneer of the Computer (Anthony Hyman).
- Irascible Genius: A Life of Charles Babbage, Inventor (Maboth Moseley).
- The Cogwheel Brain (Doron Swade). A LUV.IT educational production.

External (unrelated) links: PSP. Games. Grossisti.

This site will tell you Who is Charles Babbage, and you'll find - as well - Pictures of mathematician Charles Babbage and the Charles Babbage computer. Everything about Charles Babbage history and Charles Babbage difference engine models.
If you are asking yourself what did Charles Babbage invent, this is the ultimate place to visit. And a lot of Photos of Charles Babbage! Charles Babbage Inventions.
Interesting references and materials about Charles Babbage.

Contributions:

Written Works:

A Comparative View of the Various Institutions for the Assurance of Lives (1826)
Table of Logarithms of the Natural Numbers from 1 to 108, 000 (1827)
Reflections on the Decline of Science in England (1830)
On the Economy of Machinery and Manufactures (1832)
Ninth Bridgewater Treatise (1837)
Passages from the Life of a Philosopher (1864)

Famous Quote:

"The whole of the developments and operations of analysis are now capable of being executed by machinery. ... As soon as an Analytical Engine exists, it will necessarily guide the future course of science."

The Universal Machine

The computer is one of one of our greatest technological inventions. Its impact is—or will be—judged comparable to the wheel, the steam engine, and the printing press. But here’s the magic that makes it special: it isn’t designed to do a specific thing. It can do anything. It is a universal machine.

Software turns these universal machines into a network of ATMs, the World Wide Web, mobile phones, computers that model the universe, airplane simulators, controllers of electrical grids and communications networks, creators of films that bring the real and the imaginary to life, and implants that save lives. The only thing these technological miracles have in common is that they are all computers.

We are privileged to have lived through the time when computers became ubiquitous. Few other inventions have grown and spread at that rate, or have improved as quickly. In the span of two generations, computers have metamorphosed from enormous, slow, expensive machines to small, powerful, multi-purpose devices that are inseparably woven into our lives.

A “mainframe” was a computer that filled a room, weighed many tons, used prodigious amounts of power, and took hours or days to perform most tasks. A computer thousands of times more powerful than yesterday’s mainframe now fits into a pill, along with a camera and a tiny flashlight. Swallow it with a sip of water, and the “pill” can beam a thousand pictures and megabytes of biomedical data from your vital organs to a computer. Your doctor can now see, not just guess, why your stomach hurts.

The benefits are clear. But why look backward? Shouldn’t we focus on tomorrow?

Why Computer History?

History places us in time. The computer has altered the human experience, and changed the way we work, what we do at play, and even how we think. A hundred years from now, generations whose lives have been unalterably changed by the impact of automating computing will wonder how it all happened—and who made it happen. If we lose that history, we lose our cultural heritage.

Time is our enemy. The pace of change, and our rush to reach out for tomorrow, means that the story of yesterday’s breakthroughs is easily lost.

Compared to historians in other fields, we have an advantage: our subject is new, and many of our pioneers are still alive. Imagine if someone had done a videotaped interview of Michelangelo just after he painted the Sistine Chapel. We can do that. Generations from now, the thoughts, memories, and voices of those at the dawn of computing will be as valuable.

But we also have a disadvantage: history is easier to write when the participants are dead and will not contest your version. For us, fierce disagreements rage among people who were there about who did what, who did it when, and who did it first. There are monumental ego clashes and titanic grudges. But that’s fine, because it creates a rich goldmine of information that we, and historians who come after us, can study. Nobody said history is supposed to be easy.

It’s important to preserve the “why” and the “how,” not just the “what.” Modern computing is the result of thousands of human minds working simultaneously on solving problems. It’s a form of parallel processing, a strategy we borrowed to use for computers. Ideas combine in unexpected ways as they built on each other’s work.

Even simple historical concepts aren’t simple. What’s an invention? Breakthrough ideas sometimes seem to be “in the air” and everyone knows it. Take the integrated circuit. At least two teams of people invented it, and each produced a working model. They were working thousands of miles apart. They’d never met. It was “in the air.”

Often the process and the result are accidental. “I wasn’t trying to invent an integrated circuit,” Bob Noyce, co-inventor of the integrated circuit, was quoted as saying about the breakthrough. “I was trying to solve a production problem.” The history of computing is the history of open, inquiring minds solving big, intractable problems—even if sometimes they weren’t trying to.

The most important reason to preserve the history of computing is to help create the future. As a young entrepreneur, the story goes, Steve Jobs asked Noyce for advice. Noyce is reported to have told him that “You can’t really understand what’s going on now unless you understand what came before.”

Technology doesn’t run just on venture capital. It runs on adventurous ideas. How an idea comes to life and changes the world is a phenomenon worth studying, preserving, and presenting to future generations as both a model and an inspiration.

History Can Be Fun

Besides—computer history can be fun. An elegantly designed classic machine or a well-written software program embodies a kind of truth and beauty that give the qualified appreciative viewer an aesthetic thrill. Steve Wozniak’s hand-built motherboard for the Apple I is a beautiful painting. The source code of Apple’s MacPaint program is poetry: compressed, clear, with all parts relating to the whole. As Albert Einstein observed, “The best scientists are also artists.”

Engineers have applied incredible creativity to solve the knotty problems of computing. Some of their ideas worked. Some didn’t. That’s more than ok; it’s worth celebrating.

Silicon Valley understands that innovation thrives when it has a healthy relationship with failure. (“If at first you don’t succeed...”) Technical innovation is lumpy. It’s non-linear. Long periods of the doldrums are smashed by bursts of insight and creativity. And, like artists, successful engineers are open to the happy accident.

In other cultures, failure can be shameful. Business failure can even send you to prison. But here, failure is viewed as a possible prelude to success. Many great technology breakthroughs are inspired by crazy ideas that bombed. We need to study failures, and learn from them.

Where are all the museums?

Given the impact of computing on the human experience, it’s surprising that the Computer History Museum is one of very few institutions devoted to the subject.

There are hundreds of aircraft, railroad, and automobile museums. There are only a handful of computer museums and archives. It’s difficult to say why. Maybe the field is too new to be considered history.

We are proud of the leading role the Computer History Museum has taken in preserving the history of computing. We hope others will join us.

The kernel of our collection formed in the 1970s, when Ken Olsen of the Digital Equipment Corporation rescued sections of MIT’s Whirlwind mainframe from the scrap heap. He tried to find a home for this important computer. No institution wanted it. So he kept it and began to build his own collection around it.

Gordon Bell, also at DEC, joined the effort and added his own collection. Gordon’s wife, Gwen, attacked with gusto the task of building an institution around them. They saw, as others did not, that these early machines were important historical artifacts—treasures—that rank with Gutenberg’s press. Without Olsen and the Bells, many of the most important objects in our collection would have been lost forever.

Bob Noyce would have understood the errand we are on. Leslie Berlin’s book The Man Behind The Microchip tells the story of Noyce’s comments at a family gathering in 1972. He held up a thin silicon wafer etched with microprocessors and said, “This is going to change the world. It’s going to revolutionize your home. In your own house, you’ll all have computers. You will have access to all sorts of information. You won’t need money any more. Everything will happen electronically.”

And it is. We are living in the future he predicted.

The Computer History Museum wants to preserve not just rare and important artifacts and the stories of what happened, but also the stories of what mattered, and why. They are stories of heretics and rebels, dreamers and pragmatists, capitalists and iconoclasts—and the stories of their amazing achievements. They are stories of computing’s Golden Age, and its ongoing impact on all of us. It is an age that may have just begun.

1960/1970: IBM 7094

For its time, this was a supercomputer. IBM donated one to the Technical University in Copenhagen, where it served as the Campus Computing resource, and also made time available to other universities. This machine had 36 bit words, and I think 32 K words of main memory. The machine was very fast: Only about 3 microseconds per instruction, so rather than let the machine read punched cards and write to the printer, all the jobs and data were read onto magnetic tape and then the output was written to tape. The conversions between tape and paper or cards were done on an IBM1401, which was later replaced with an IBM-360/30 which could accept jobs remotely via modems.The operating system of the 7094 was called IBSYS and lived on a tape drive. It had many compilers, including Fortran II, Fortran IV and COBOL.
(A reference manual for the very similar IBM 7090 is here - PDF, 156 pages).

1965/1970: RC-4000

The RC-4000 was the successor to the GIER, but had nothing in common with it. It was a 24-bit machine with a real-time operating system that had interrupts, memory protection and a limited amount of multi-tasking. It was used for many interesting applications, including real-time chemical process control, large databases (telephone directory call-centers) and time-sharing. The operating system was the subject of a fair number of computer science research journal articles, and many of the concepts embodied in it were absorbed into Multics and Unix. The one we used at Univeristy of Copenhagen belonged to the Chemistry department, but time-sharing terminals were found all over the science campus section, where they served other departments until the Univac 1106 arrived.

1968/1972: IBM 360

The IBM-360 family of computers ranged from the model 20 minicomputer (which typically had 24 KB of memory) to the model 91 supercomputer which was built for the North American missile defense system. Despite their differences, all these machines had the same user instruction set; on the smaller machines many of the more complex instructions were done in microcode rather than in hardware. For example, machines in the lower midrange did not have multiplier hardware, but the microcode implemented multiplications by repeated addition. It was rumored that the smallest machines did addition by repeated increments!The machines had different operating systems. The smallest machines could not really support an operating system and were often used for specialized applications, where a program was loaded from binary punched cards at startup. The middle range used a system called DOS (not related to MS-DOS) and the higher end system was called OS/360. These were the machines that established 32 bits as the standard for computers.
The first IBM-360 I used in Copenhagen was the spooling front-end for the 7094. In 1970, the technical university installed a 360/65, later upgraded to a 360/75. When it came in, it had 1 MB of RAM (magnetic core memory in those days) and a roomful of disk drives, probably adding up to about 200 MB.
Today's S/390 mainframes are direct descendants of the IBM-360 family.

1968/1970: IBM 1130

The IBM-1130 was a mini-computer built in the shape of a desk. The ALU had 16-bit words, and it came with a 1.5 MB hard disk. The DOS had a Fortran-IV compiler, but even though the machine was similarly sized to the GIER, it was much less usable.Eventually, the Niels Bohr Institute decided that it could be used as remote job entry terminal to the IBM computers at the technical university.

1965/1970: Univac 1100 Series

The Danish universities decided to install 3 large computers at the three largest univerities, an they wisely chose to get an IBM, an UNIVAC and a Control Data. University of Copenhagen got the Univac, and it was a great system.When the machine was installed, it was a Univac-1106 with 131 K words (of 36 bits), i.e. about 600 KB. About 18 months later, it was upgraded to an 1108 which ran twice as fast. This upgrade consisted in replacing a divide-by-two flip-flop in the system clock circuit by a jumper. We also got more memory, I think we doubled it.
This machine served an endless stream of batch jobs from both local and remote card-reader/printer stations plus about 50 interactive display terminals.

UNISYS History Newsletter has several good articles about these machines.

CDC 6500

PDP-11

Digital Equipment Corporation's PDP-11 family of minicomputers was extremely successful for over 25 years - for good reasons. The instruction set was elegant and flexible, the engineering design was modular in ways that not only allowed the manufacturer to custom build machines of many different price/performance levels, but also allowed users to expand them in the field later. Machines existed in all differnet sizes; towards the end of its lifespan, the range spanned from personal computers built into a terminal, to time-sharing multiuser systems capable of serving as a common computing resource for an entire university department.Read more on my PDP-11 page.

1978/1981: VAX Family

The PDP-11 address space eventually became too small to do practical work: As the machines got less expensive, people were attacking more complex problems, requiring larger programs. So Digital Equipment built a larger machine, called VAX-11 (Virtual Address eXtensions for pdp-11). This machine was the best design I have ever worked on. The instruction set was very powerful, although some thought it was too large to be truly elegant.Read more on my VAX page.

Sun 3

When I changed employers in 1990, one of the attractions of the new job was that instead of a text terminal connected to a central computer cluster, this company put a workstation with a bit-mapped windowed display on the desk of each engineer. In those days, that would be a Sun Microsystems Sun-3/80.Sun Microsystems was a company built on the discovery that single-chip microprocessors had become powerful enough that one could build a general- purpose computer around one of these chips, powerful enough to tackle the same class of problems that one would have done on a mainframe or a VAX, but inexpensive enough to give one for the exclusive use of a scientist or engineer. Programmers loved them. They ran the same Unix systems that was used on many PDP-11 or VAX sites, were programmed in the "C" programming language, and on the windowed screen you could have 5 or 6 windows, each looking like a terminal and switch your keyboard back and forth between them.
My new employer built communications equipment around the same family of Motorola microprocessors, and we used the compilers and other software development tools of the Sun machines.

1984/1989: Apple 68000 MacIntosh

The MacIntosh took the ideas behind the Sun and applied them to systems more suited to consumers: Half the price, and as easy to use as possible. The MacIntosh did not "invent" or even popularize the mouse: The Sun had a mouse. What was new was the desktop metaphor as a way of organizing the workspace, and the removal of command lines: Clicking on the pictures was the ONLY way to run programs.I loved the Macs from I first saw one, but I thought this was way too much money to spend on a toy. My wife and I bought one in 1989, when a brother-in-law who managed a computer store got a good offer for a demonstration system, which he passed along to us. Our machine was called the Mac SE; it had one MB of DRAM and a 20MB hard drive, and cost USD 2000.
Ironically, one of the things that I found attractive about it was the knowledge that programming for the Mac was very difficult, and the machine did not come with any compiler or other programming tools. Thus I was guaranteed not to be tempted into spending all my spare time playing with the computer, but would be able to enjoy it as a tool.

Sun 4 (SPARC)

The MC68000 was a nice enough CPU, but Sun Microsystems decided they could build a much more powerful system for not much more money by designing their own CPU according to the "RISC" (Reduced Instruction Set Computer) architecture fashion of the time. Sun called their RISC design SPARC (which they said stood for something Sun Processor Architecture for RISC Computing).The idea behind RISC was to make the instructions simple enough that every instruction could complete in one cycle of the master clock. You might execute a few more instructions that way, but since the CPU logic would be simpler, you could use the circuitry space that was saved on the CPU chip to include a larger cache memory, so fewer of the instructions and data fetched from memory would have to come from the main memory. This would allow the programs to run faster.
In general, RISC computers were unfriendly to programmers that wanted to write "assembly language" where the programmer has to describe the operations in terms of individual machine instructions. But most programmers very rarely do that. So with a good C compiler, the "weird" instruction sets did not matter.
The first SPARC machines came out around 1989 and allowed Sun to build larger servers to complement their desktop machines. Within 2-3 years, a smaller, less expensive RISC CPU was replacing the MC68000 chips in the desktop workstations.

Intel x86 Family

The Intel 8088 microprocessor was chosen by IBM for their first Personal Computer in 1980. Soon many manufacturers were building very similar machines, using also the slightly faster 8086 and 80186 CPU versions. Around 1982, the PC-AT (advanced technology) came out with the 80286 CPU. After interesting video games became available (beginning with the Microsoft Flight Simulator) every manufacturer had to make their machine indistinguishable from the PC-AT in order that it would be able to run these games. Soon the intense competition among the smaller manufacturers in Taiwan drove the prices of the look-alike "PC clones" well below the price of "real" PCs, and the market really took off.After the MacIntosh stunned the market, IBM and Microsoft worked feverishly to produce a "Windows program" for PCs, and after several very bad versions, Microsoft Windows version 3.1 finally became a good enough imitation around 1990.
Meanwhile, Intel kept producing faster and better microprocessors, still compatible with the 8088/8086/80286 series, although the later versions beginning with 80386 also had a newer memory management system that allowed them to run Unix. Beginning around 1988, Unix was ported to 80386 PCs.
Today, PCs range from small portable ("laptop") computers to large server machines with 4-way multiprocessor CPU sets and can run any of these operating systems (plus several less common):

Windows 98 (95, 3.1)
Windows NT (2000)
Linux (Red Hat, SuSe, Debian)
FreeBSD (NetBSD, BSDi)
OS/2
BeOS

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COMPUTER HISTORY GLOBALLY

1960/1969: RC-GIER
The GIER computer was built by the long-departed Danish computer manufacturer RegneCentralen. In those days, computers were large and hand-built in small numbers for lots of money. The GIER was considered very successful. I think they built about 40 of them over a 6-year period. I did not actually get my hands on these until 1970, when I enrolled at University of Copenhagen, where the Math department had two in their basement, and the Niels Bohr Institute of Physics had another one.The GIER machines were compact and handsome for their time. The cabinet was about 200 cm high (6.5 feet), 220 cm (just over 7 feet) long and about 60 cm (2 feet) deep. The two broad sides each had 3 sliding teakwood panels, the ends were a light gray-brown enamel, and off to one side was a desk console with a high-speed papertape reader (2000 cps, optical) to the left, a slanted bakelite panel with lights, switches and a loudspeaker to the right, and an electric typewriter in the middle.
The machines had 42-bit words (40 bits of arithmetic precision and two "flag bits"). They had 1024 words of this, with an optional 4096 additional words of "buffer memory" which could not be directly addressed, but could be block copied in and out of main memory. They also had a magnetic drum with 960 tracks, each of which could hold 40 words. This adds up to about 200 kilobytes of storage. Amazingly, they packed onto that drum a small operating system, an Algol-60 compiler and a runtime library with virtual memory management (for code segments only). The machines were quite usable, and were used both for undergraduate instruction in computer programming and for many research projects including weather modeling.

HISTORY OF COMPUTER IN NEPAL

There is not a long history of computers in Nepal.Nepal hired some types of calculators and computers for it's census calculation.Following list shows it's history in Nepal.· In 2018 BS an electronic calculator called "Facit" was used for census.· In 2028 BS census IBM 1401 a second generation mainframe computer was used.· In 2031 BS a center for Electronic Data Processing ,Later renamed to National Computer Center(NCC),was established for national data processing and computer training.· In 2038 BS ICL 2950/10 a second generation mainframe computer was used for census.· Now-a-days probably each and every institutions,business organizations,communication centers,ticket counters etc are using computers.

ms word:

Microsoft Office Word is a word processing software licensed by Microsoft and is usually included in the Microsoft Office suites with other desktop applications like Microsoft Excel and PowerPoint. It is somehow also available in a standalone version thatâ€(TM)s costs around $200. Since its release in 1983, Microsoft has launched versions of the program that were compatible with DOS, Windows and Mac operating systems.

The Microsoft Office suite must be purchased either from the installation CD licensed by Microsoft or downloaded from the official website. http://office.microsoft.com/en-us/downloads/default.aspx

Download Link: http://www.jarte.com/download.html

http://www.koffice.org/download/

microsoft Word Viewer 97-2000 is a download that lets users who do not own Microsoft Word view and print documents that were created in Word. Word 97-2000 Viewer can open documents that were created with all earlier versions of Word for Windows and with version 4.xand later versions of Microsoft Word for Macintosh.

Before December 15, 2004, there were two versions of Microsoft Word Viewer 97-2000 available for download: a 16-bit Windows version and a 32-bit Windows version. Both of these downloads are replaced by a newer version of the Microsoft Word Viewer. For additional information about how to obtain the latest version of Microsoft Word Viewer, click the following article number to view the article in the Microsoft Knowledge Base:

891090 How to obtain the latest Microsoft Word Viewer

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MORE INFORMATION

Features of Microsoft Word Viewer 97-2000

Microsoft Word Viewer 97-2000 is optimized for displaying Word documents in Microsoft Internet Explorer 3.x and later versions. Word Viewer 97-2000 includes the following features:

Online layout view for easy reading of online documents, including those with background colors and textures.
Document Map for point-and-click navigation through longer documents.
Hyperlink navigation to open any hyperlink in a document by using your default browser.
You cannot run macros in any version of Word Viewer. This means that you cannot receive a Word macro virus by reading a document with Word Viewer.
You cannot edit an open document in Word Viewer. However, you can copy text to the Clipboard to paste it to other applications. Microsoft encourages you to distribute Word Viewer together with your Word documents to people who do not have Microsoft Word.

Note You can use Microsoft Word Viewer 97-2000 to view documents that were created in Microsoft Word 97, in Microsoft Word 2000, in Microsoft Word 2002, and in Microsoft Office Word 2003. However, advanced features that are available in Word 2000, in Word 2002, and in Word 2003 may not appear correctly in Word Viewer 97-2000. Some examples include nested tables, text wrapping around tables, Web frame pages, and advanced Web formatting.

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Troubleshooting

If you installed Microsoft Word Viewer and are observing unusual behavior, reinstall it by using the appropriate method for your operating system.

Windows 95 or Windows NT 4.0 or a later version:

Click Start, point to Control Panel, and then double-click Add/Remove Programs.
Click the Install/Uninstall tab.
Double-click Microsoft Word Viewer, and then follow the directions that appear.

Windows 3.1 or Windows NT 3.51:

Go to directory where Word Viewer is installed.
Run the Setup.exe file.

Setup always displays a dialog box with a Reinstall button to restore any missing files or settings. Click this button to start the reinstallation.

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Uninstalling Word Viewer

To remove Word Viewer from your system, start Word Viewer Setup as described earlier in this article, and then click Remove All. After the uninstall is complete, start Word to restore its settings.

Creating Mathematics inside Microsoft Word

There are four sections to this document

Before you can use the Equation Editor
(Very) Basic operation of the Equation Editor
Shortcut Keys are your very best friend
Simonds tips on using the equation editor

Before you can use the Equation EditorThe other three sections of this document will work only if the Microsoft Equation Editor has been installed on the machine you are using; the Equation Editor comes with Microsoft Office but is not installed under a standard installation. The computers in the Sylvania CRC and Sylvania math classrooms all have the Equation Editor installed. On your home machine you probably will need to load your Microsoft office CD and do a custom install to install the Equation Editor. (It's easier to do than the phrase "custom install" implies. J ) All of the maneuvers described in this section of the document will need to be done at most once.
After installing the Equation Editor, you also want to customize your toolbar so that the Equation Editor button

is easily accessible. (The button is already on the CRC and math classroom machines.)

The menu shown in Figure 1 was opened by selecting Tools - Customize from the toolbar menu across the top of the screen, then selecting the commandsfile-tab at the top of the dialogue box, then selecting the insert category on the left side of the box, and finally scrolling down on the right-side of the box until the Equation Editor button was in view. Once you have located the Equation Editor button, left-click and drag the button up to your toolbar menu.

You can get some limited memory information from the Runtime class. It really isn't exactly what you are looking for, but I thought I would provide it for the sake of completeness. Here is a small example. Edit: You can also get disk usage information from the java.io.File class. The disk space usage stuff requires Java 1.6 or higher.

public class Main {
  public static void main(String[] args) {
    /* Total number of processors or cores available to the JVM */
    System.out.println("Available processors (cores): " + 
        Runtime.getRuntime().availableProcessors());

    /* Total amount of free memory available to the JVM */
    System.out.println("Free memory (bytes): " + 
        Runtime.getRuntime().freeMemory());

    /* This will return Long.MAX_VALUE if there is no preset limit */
    long maxMemory = Runtime.getRuntime().maxMemory();
    /* Maximum amount of memory the JVM will attempt to use */
    System.out.println("Maximum memory (bytes): " + 
        (maxMemory == Long.MAX_VALUE ? "no limit" : maxMemory));

    /* Total memory currently in use by the JVM */
    System.out.println("Total memory (bytes): " + 
        Runtime.getRuntime().totalMemory());

    /* Get a list of all filesystem roots on this system */
    File[] roots = File.listRoots();

    /* For each filesystem root, print some info */
    for (File root : roots) {
      System.out.println("File system root: " + root.getAbsolutePath());
      System.out.println("Total space (bytes): " + root.getTotalSpace());
      System.out.println("Free space (bytes): " + root.getFreeSpace());
      System.out.println("Usable space (bytes): " + root.getUsableSpace());
    }
  }
}


25down vote The java.lang.management package does give you a whole lot more info than Runtime - for example it will give you heap memory (ManagementFactory.getMemoryMXBean().getHeapMemoryUsage()) separate from non-heap memory (ManagementFactory.getMemoryMXBean().getNonHeapMemoryUsage()).
You can also get process CPU usage (without writing your own JNI code), but you need to cast thejava.lang.management.OperatingSystemMXBean to acom.sun.management.OperatingSystemMXBean. This works on Windows and Linux, I haven't tested it elsewhere.
For example ... call the get getCpuUsage() method more frequently to get more accurate readings.
public class PerformanceMonitor { 
    private int  availableProcessors = getOperatingSystemMXBean().getAvailableProcessors();
    private long lastSystemTime      = 0;
    private long lastProcessCpuTime  = 0;

    public synchronized double getCpuUsage()
    {
        if ( lastSystemTime == 0 )
        {
            baselineCounters();
            return;
        }

    long systemTime     = System.nanoTime();
    long processCpuTime = 0;

    if ( getOperatingSystemMXBean() instanceof OperatingSystemMXBean )
    {
        processCpuTime = ( (OperatingSystemMXBean) getOperatingSystemMXBean() ).getProcessCpuTime();
learning things

JavaScript History & Information
JavaScript is considered to be one of the most powerful scripting languages in use today. It is often used for the development of client-side web development. Do you know that JavaScript is also sometimes called as ECMAScript because it strictly adheres to the ECMAScript standard? JavaScript is used to make web pages more interactive and dynamic. JavaScript is a light weight programming language and it is embedded directly into the HTML code. JavaScript, as the name suggests, was influenced by many languages, especially Java.
Been trying to teach myself some web design and programing language
JavaScript is one of the most well-known trademarks in the web development world; it is the trademark of Sun Microsystems. It was originally invented by Netscape and was kept under license for some time but now you are not required to get a license in order to use JavaScript. Most of the learners ask about what JavaScript can do for them. Well, let’s briefly review what JavaScript can do for us:
Leaning tower of nerd knowledge
HTML designers use JavaScript as one of the best programming tool that is very simple, syntax wise, and need not to have any previous strong programming skills because most of the HTML authors are not programmers. However, the syntax of JavaScript is so simple that most of the HTML authors easily play with it.
JavaScript can be used to make HTML pages more dynamic. All plain HTML files are static.
JavaScript has the ability to react to various events which is not possible through HTML. When a use clicks a button, an action event can be generated with the help of JavaScript
JavaScript can be embedded easily into an HTML document and JavaScript easily reads and can write HTML elements as well
If you want to detect the browser of the visitor, you can use JavaScript and can load the page according to the requirement of that browser.
Cookies can be created using JavaScript
You can add various other features like user validation, authentication etc by the use of JavaScript.
These were some the main features of JavaScript that were briefly described above; now let’s have a brief look at the history of JavaScript.
JavaScript was developed by Brendan Eich, who worked for Netscape and he named JavaScript initially as Mocha. After a while, Mocha was renamed as LiveScript and finally it was renamed to JavaScript as we know it today. Because Netscape added the Java Technology in its web browser; that is reason LiveScript name was changed to JavaScript. It was in the year 1995 when JavaScript was first deployed in the browser of Netscape; the Netscape Navigator version 2.0B3. Soon after its success, Microsoft also tried it but used a different name; Jscript in order to avoid any possible trademark issues later. The Jscript was first deployed in Internet Explorer 3.0 which was introduced in the year 1996. After its introduction, Jscript or JavaScript has undergone many changes and improvements and has become one of the most powerful scripting languages for the web.
Let’s now refresh some basic concepts of JavaScript, after that we will move towards some experimentation with JavaScript.
JavaScript is a scripting language that is mainly used in order to add interactivity to the HTML pages
Remember that scripting language is not like ordinary computer programming languages; scripting languages are light weight programming languages.
JavaScript is embedded directly in to the markup code or the HTML code.
One of the main advantages of using JavaScript is that it is an interpreted language in which scripts are directly executed without preliminary compilation.
You are not required to purchase a license in order to use JavaScript.
After brief revision, we can head towards some experimentation. Carefully go through the following steps that will guide you about how to make your first, very basic, JavaScript code;
The first thing you need to make sure is that you get some idea about markup languages like HTML/XHTML. Once you are done with them, you are ready for some Java Scripting.
Open any text editor like Notepad for writing HTML tags.
JavaScript code is embedded directly in the HTML file.
JavaScript code opens with <Script> and ends with </Script>
You have to define the script type inside the Script tag; <Script type=”text/JavaScript”>
Write down the following piece of code in order to display Hello World on the HTML page
<html>
<body>
<script type=”text/javascript”>
document.write(“Hello World”);
</script>
</body>
</html>
This piece of code, using the write function, will display Hello World¸ on the HTML Page. Document.write is a JavaScript command used for writing any output to the html page. This is one of the simplest examples that almost every new learner come across during the learning of JavaScript. For more information about JavaScript and learning of JavaScript, follow our further sections that will guide you in choosing better online learning resources for JavaScript

JS HOME JS Introduction JS How To JS Where To JS Statements JS Comments JS Variables JS Operators JS Comparisons JS If...Else JS Switch JS Popup Boxes JS Functions JS For Loop JS While Loop JS Break Loops JS For...In JS Events JS Try...Catch JS Throw JS Special Text JS Guidelines  

JS Objects
JS Objects Intro JS String JS Date JS Array JS Boolean JS Math JS RegExp  

JS Advanced
JS Browser JS Cookies JS Validation JS Animation JS Image Maps JS Timing JS Create Object JS Summary  

JS Examples
JS Examples JS Objects Examples JS Browser Examples JS DOM Examples JS Quiz JS Certificate  

JS References
JavaScript Objects HTML DOM Objects 
JavaScript Tutorial

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JavaScript is used in millions of Web pages to add functionality, validate forms, detect browsers, and much more.
Start learning JavaScript now!
Examples in Each Chapter
This JavaScript tutorial contains more than 200 examples!
With our online editor, you can edit the JavaScript code, and click on a button to view the result.

Example

<html> <body>  <script type="text/javascript"> document.write("This is my first JavaScript!"); </script>  </body> </html>
Try it yourself »
Click on the "Try it Yourself" button to see how it works.
JavaScript Examples
Learn by 200 examples!
With our editor, you can edit the source code, and click on a test button to view the result.
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JavaScript Quiz Test
Test your JavaScript skills at W3Schools!
Start JavaScript Quiz! 
JavaScript References
At W3Schools you will find a complete reference of all JavaScript objects, Browser objects, and the HTML DOM objects. Contains lot of examples!
JavaScript Built-in objects
Browser objects
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JavaScript Exam - Get Your Diploma!

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Computer virus
From Wikipedia, the free encyclopedia
Not to be confused with Malware.
A computer virus is a computer program that can copy itself^[1] and infect a computer. The term "virus" is also commonly but erroneously used to refer to other types of malware, including but not limited to adware and spyware programs that do not have the reproductive ability. A true virus can spread from one computer to another (in some form of executable code) when its host is taken to the target computer; for instance because a user sent it over a network or the Internet, or carried it on a removable medium such as a floppy disk, CD, DVD, or USB drive.^[2]
Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by another computer.^[3]^[4]
As stated above, the term "computer virus" is sometimes used as a catch-all phrase to include all types of malware, even those that do not have the reproductive ability. Malware includes computer viruses, computer worms, Trojan horses, most rootkits, spyware, dishonest adware and other malicious and unwanted software, including true viruses. Viruses are sometimes confused with worms and Trojan horses, which are technically different. A worm can exploit security vulnerabilities to spread itself automatically to other computers through networks, while a Trojan horse is a program that appears harmless but hides malicious functions. Worms and Trojan horses, like viruses, may harm a computer system's data or performance. Some viruses and other malware have symptoms noticeable to the computer user, but many are surreptitious or simply do nothing to call attention to themselves. Some viruses do nothing beyond reproducing themselves.
HOW IT'S DONE
Here's the entire page, minus my comments. Take a few minutes to learn as much as you can from this, then I'll break it down into smaller pieces.
<HTML>
<HEAD>
<SCRIPT LANGUAGE="JavaScript">
<!-- Beginning of JavaScript -
function MsgBox (textstring) {
alert (textstring) }
// - End of JavaScript - -->
</SCRIPT>
</HEAD>
<BODY><FORM><INPUT NAME="text1" TYPE=Text>
<INPUT NAME="submit" TYPE=Button VALUE="Show Me" onClick="MsgBox(form.text1.value)">
</FORM>
</BODY>
</HTML>
http://www.webteacher.com please do visit this site!!!!!!!!!!!!!!
    }

    double cpuUsage = (double) ( processCpuTime - lastProcessCpuTime ) / ( systemTime - lastSystemTime );

    lastSystemTime     = systemTime;
    lastProcessCpuTime = processCpuTime;

    return cpuUsage / availableProcessors;
}
private void baselineCounters()
{
    lastSystemTime = System.nanoTime();

 think the best method out there is to implement the SIGAR API by Hyperic. It works for most of the major operating systems ( darn near anything modern ) and is very easy to work with. The developer(s) are very responsive on their forum and mailing lists. I also like that it is GPL2. They provide a ton of examples in Java too!
SIGAR == System Information, Gathering And Reporting tool.

link|edit|flag answered Aug 25 '08 at 2:36
Matt Cummings 751515



up vote3down vote Have a look at the APIs available in the java.lang.management package. For example:
OperatingSystemMXBean.getSystemLoadAverage()
ThreadMXBean.getCurrentThreadCpuTime()
ThreadMXBean.getCurrentThreadUserTime()
There are loads of other useful things in there as well.

link|edit|flag answered Aug 26 '08 at 7:09
staffan 1,090514


OperatingSystemMXBean.getSystemLoadAverage() is not implemented in windows because "its too expensive"– MikeNereson Jul 14 '09 at 15:36
ThreadMXBean.getCurrentThreadCpuTime() only returns how long that thread has been running. Not the cpu usage percentage. – MikeNereson Jul 14 '09 at 15:37


up vote3down vote CPU usage isn't straightforward -- java.lang.management via com.sun.management.OperatingSystemMXBean.getProcessCpuTime comes close (see Patrick's excellent code snippet above) but note that it only gives access to time the CPU spent in your process. it won't tell you about CPU time spent in other processes, or even CPU time spent doing system activities related to your process.
for instance i have a network-intensive java process -- it's the only thing running and the CPU is at 99% but only 55% of that is reported as "processor CPU".
don't even get me started on "load average" as it's next to useless, despite being the only cpu-related item on the MX bean. if only sun in their occasional wisdom exposed something like "getTotalCpuTime"...
for serious CPU monitoring SIGAR mentioned by Matt seems the best bet.

link|edit|flag answered Jun 2 '09 at 2:01
Partly Cloudy 1162



up vote2down vote Hey you can do this with java/com integration. By accessing WMI features you can get all the information.

link|edit|flag answered Mar 24 '09 at 12:32
Sudhi



up vote1down vote Usually, to get low level OS information you can call OS specific commands which give you the information you want with Runtime.exec() or read files such as /proc/* in Linux.

link|edit|flag answered Mar 24 '09 at 19:43
Peter Lawrey 16.6k11320



up vote1down vote There's a new native Java project that uses JNA (so no native libraries). It's very young and needs contributions.
http://oshi.codeplex.com

link|edit|flag

 

 



History
Academic work
The first academic work on the theory of computer viruses (although the term "computer virus" was not invented at that time) was done by John von Neumann in 1949 who held lectures at the University of Illinois about the "Theory and Organization of Complicated Automata". The work of von Neumann was later published as the "Theory of self-reproducing automata".^[5] In his essay von Neumann postulated that a computer program could reproduce.
In 1972 Veith Risak published his article "Selbstreproduzierende Automaten mit minimaler Informationsübertragung" (Self-reproducing automata with minimal information exchange).^[6] The article describes a fully functional virus written in assembler language for a SIEMENS 4004/35 computer system.
In 1980 Jürgen Kraus wrote his diplom thesis "Selbstreproduktion bei Programmen" (Self-reproduction of programs) at the University of Dortmund.^[7] In his work Kraus postulated that computer programs can behave in a way similar to biological viruses.
In 1984 Fred Cohen from the University of Southern California wrote his paper "Computer Viruses - Theory and Experiments".^[8] It was the first paper to explicitly call a self-reproducing program a "virus"; a term introduced by his mentor Leonard Adleman.
An article that describes "useful virus functionalities" was published by J. B. Gunn under the title "Use of virus functions to provide a virtual APL interpreter under user control" in 1984.^[9]
Science Fiction
The Terminal Man, a science fiction novel by Michael Crichton (1972), told (as a sideline story) of a computer with telephone modem dialing capability, which had been programmed to randomly dial phone numbers until it hit a modem that is answered by another computer. It then attempted to program the answering computer with its own program, so that the second computer would also begin dialing random numbers, in search of yet another computer to program. The program is assumed to spread exponentially through susceptible computers.
The actual term 'virus' was first used in David Gerrold's 1972 novel, When HARLIE Was One. In that novel, a sentient computer named HARLIE writes viral software to retrieve damaging personal information from other computers to blackmail the man who wants to turn him off.
Virus programs
The Creeper virus was first detected on ARPANET, the forerunner of the Internet, in the early 1970s.^[10] Creeper was an experimental self-replicating program written by Bob Thomas at BBN Technologies in 1971.^[11] Creeper used the ARPANET to infect DEC PDP-10 computers running the TENEX operating system.^[12] Creeper gained access via the ARPANET and copied itself to the remote system where the message, "I'm the creeper, catch me if you can!" was displayed. The Reaper program was created to delete Creeper.^[13]
A program called "Elk Cloner" was the first computer virus to appear "in the wild" — that is, outside the single computer or lab where it was created.^[14] Written in 1981 by Richard Skrenta, it attached itself to the Apple DOS 3.3 operating system and spread via floppy disk.^[14]^[15] This virus, created as a practical joke when Skrenta was still in high school, was injected in a game on a floppy disk. On its 50th use the Elk Cloner virus would be activated, infecting the computer and displaying a short poem beginning "Elk Cloner: The program with a personality."
The first PC virus in the wild was a boot sector virus dubbed (c)Brain,^[16] created in 1986 by the Farooq Alvi Brothers in Lahore, Pakistan, reportedly to deter piracy of the software they had written.^[17]
Before computer networks became widespread, most viruses spread on removable media, particularly floppy disks. In the early days of the personal computer, many users regularly exchanged information and programs on floppies. Some viruses spread by infecting programs stored on these disks, while others installed themselves into the disk boot sector, ensuring that they would be run when the user booted the computer from the disk, usually inadvertently. PCs of the era would attempt to boot first from a floppy if one had been left in the drive. Until floppy disks fell out of use, this was the most successful infection strategy and boot sector viruses were the most common in the wild for many years.^[1]
Traditional computer viruses emerged in the 1980s, driven by the spread of personal computers and the resultant increase in BBS, modem use, and software sharing. Bulletin board-driven software sharing contributed directly to the spread of Trojan horse programs, and viruses were written to infect popularly traded software. Shareware and bootleg software were equally common vectors for viruses on BBS's.^{[citation needed]}
Macro viruses have become common since the mid-1990s. Most of these viruses are written in the scripting languages for Microsoft programs such as Word and Excel and spread throughoutMicrosoft Office by infecting documents and spreadsheets. Since Word and Excel were also available for Mac OS, most could also spread to Macintosh computers. Although most of these viruses did not have the ability to send infected e-mail, those viruses which did take advantage of the Microsoft Outlook COM interface.^{[citation needed]}
Some old versions of Microsoft Word allow macros to replicate themselves with additional blank lines. If two macro viruses simultaneously infect a document, the combination of the two, if also self-replicating, can appear as a "mating" of the two and would likely be detected as a virus unique from the "parents".^[18]
A virus may also send a web address link as an instant message to all the contacts on an infected machine. If the recipient, thinking the link is from a friend (a trusted source) follows the link to the website, the virus hosted at the site may be able to infect this new computer and continue propagating.
Viruses that spread using cross-site scripting were first reported in 2002,^[19] and were academically demonstrated in 2005.^[20] There have been multiple instances of the cross-site scripting viruses in the wild, exploiting websites such as MySpace and Yahoo.
Symptoms of a computer virus
If you suspect or confirm that your computer is infected with a computer virus, obtain the current antivirus software. The following are some primary indicators that a computer may be infected:

The computer runs slower than usual.
The computer stops responding, or it locks up frequently.
The computer crashes, and then it restarts every few minutes.
The computer restarts on its own. Additionally, the computer does not run as usual.
Applications on the computer do not work correctly.
Disks or disk drives are inaccessible.
You cannot print items correctly.
You see unusual error messages.
You see distorted menus and dialog boxes.
There is a double extension on an attachment that you recently opened, such as a .jpg, .vbs, .gif, or .exe. extension.
An antivirus program is disabled for no reason. Additionally, the antivirus program cannot be restarted.
An antivirus program cannot be installed on the computer, or the antivirus program will not run.
New icons appear on the desktop that you did not put there, or the icons are not associated with any recently installed programs.
Strange sounds or music plays from the speakers unexpectedly.
A program disappears from the computer even though you did not intentionally remove the program.
Note These are common signs of infection. However, these signs may also be caused by hardware or software problems that have nothing to do with a computer virus. Unless you run the Microsoft Malicious Software Removal Tool, and then you install industry-standard, up-to-date antivirus software on your computer, you cannot be certain whether a computer is infected with a computer virus or not.

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Symptoms of worms and trojan horse viruses in e-mail messages
When a computer virus infects e-mail messages or infects other files on a computer, you may notice the following symptoms:

The infected file may make copies of itself. This behavior may use up all the free space on the hard disk.
A copy of the infected file may be sent to all the addresses in an e-mail address list.
The computer virus may reformat the hard disk. This behavior will delete files and programs.
The computer virus may install hidden programs, such as pirated software. This pirated software may then be distributed and sold from the computer.
The computer virus may reduce security. This could enable intruders to remotely access the computer or the network.
You receive an e-mail message that has a strange attachment. When you open the attachment, dialog boxes appear, or a sudden degradation in system performance occurs.
Someone tells you that they have recently received e-mail messages from you that contained attached files that you did not send. The files that are attached to the e-mail messages have extensions such as .exe, .bat, .scr, and .vbs extensions.
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Symptoms that may be the result of ordinary Windows functions
A computer virus infection may cause the following problems:

Windows does not start even though you have not made any system changes or even though you have not installed or removed any programs.
There is frequent modem activity. If you have an external modem, you may notice the lights blinking frequently when the modem is not being used. You may be unknowingly supplying pirated software.
Windows does not start because certain important system files are missing. Additionally, you receive an error message that lists the missing files.
The computer sometimes starts as expected. However, at other times, the computer stops responding before the desktop icons and the taskbar appear.
The computer runs very slowly. Additionally, the computer takes longer than expected to start.
You receive out-of-memory error messages even though the computer has sufficient RAM.
New programs are installed incorrectly.
Windows spontaneously restarts unexpectedly.
Programs that used to run stop responding frequently. Even if you remove and reinstall the programs, the issue continues to occur.
A disk utility such as Scandisk reports multiple serious disk errors.
A partition disappears.
The computer always stops responding when you try to use Microsoft Office products.
You cannot start Windows Task Manager.
Antivirus software indicates that a computer virus is present.
Note These problems may also occur because of ordinary Windows functions or problems in Windows that are not caused by a computer virus.

Infection strategies
In order to replicate itself, a virus must be permitted to execute code and write to memory. For this reason, many viruses attach themselves to executable files that may be part of legitimate programs. If a user attempts to launch an infected program, the virus' code may be executed simultaneously. Viruses can be divided into two types based on their behavior when they are executed. Nonresident viruses immediately search for other hosts that can be infected, infect those targets, and finally transfer control to the application program they infected. Resident viruses do not search for hosts when they are started. Instead, a resident virus loads itself into memory on execution and transfers control to the host program. The virus stays active in the background and infects new hosts when those files are accessed by other programs or the operating system itself.
Nonresident viruses
Nonresident viruses can be thought of as consisting of a finder module and a replication module. The finder module is responsible for finding new files to infect. For each new executable file the finder module encounters, it calls the replication module to infect that file.
Resident viruses
Resident viruses contain a replication module that is similar to the one that is employed by nonresident viruses. This module, however, is not called by a finder module. The virus loads the replication module into memory when it is executed instead and ensures that this module is executed each time the operating system is called to perform a certain operation. The replication module can be called, for example, each time the operating system executes a file. In this case the virus infects every suitable program that is executed on the computer.
Resident viruses are sometimes subdivided into a category of fast infectors and a category of slow infectors. Fast infectors are designed to infect as many files as possible. A fast infector, for instance, can infect every potential host file that is accessed. This poses a special problem when using anti-virus software, since a virus scanner will access every potential host file on a computer when it performs a system-wide scan. If the virus scanner fails to notice that such a virus is present in memory the virus can "piggy-back" on the virus scanner and in this way infect all files that are scanned. Fast infectors rely on their fast infection rate to spread. The disadvantage of this method is that infecting many files may make detection more likely, because the virus may slow down a computer or perform many suspicious actions that can be noticed by anti-virus software. Slow infectors, on the other hand, are designed to infect hosts infrequently. Some slow infectors, for instance, only infect files when they are copied. Slow infectors are designed to avoid detection by limiting their actions: they are less likely to slow down a computer noticeably and will, at most, infrequently trigger anti-virus software that detects suspicious behavior by programs. The slow infector approach, however, does not seem very successful.
Vectors and hosts
Viruses have targeted various types of transmission media or hosts. This list is not exhaustive:
Binary executable files (such as COM files and EXE files in MS-DOS, Portable Executable files in Microsoft Windows, the Mach-O format in OSX, and ELF files in Linux)
Volume Boot Records of floppy disks and hard disk partitions
The master boot record (MBR) of a hard disk
General-purpose script files (such as batch files in MS-DOS and Microsoft Windows, VBScript files, and shell script files on Unix-like platforms).
Application-specific script files (such as Telix-scripts)
System specific autorun script files (such as Autorun.inf file needed by Windows to automatically run software stored on USB Memory Storage Devices).
Documents that can contain macros (such as Microsoft Word documents, Microsoft Excel spreadsheets, AmiPro documents, and Microsoft Access database files)
Cross-site scripting vulnerabilities in web applications (see XSS Worm)
Arbitrary computer files. An exploitable buffer overflow, format string, race condition or other exploitable bug in a program which reads the file could be used to trigger the execution of code hidden within it. Most bugs of this type can be made more difficult to exploit in computer architectures with protection features such as an execute disable bit and/or address space layout randomization.
PDFs, like HTML, may link to malicious code. PDFs can also be infected with malicious code.
In operating systems that use file extensions to determine program associations (such as Microsoft Windows), the extensions may be hidden from the user by default. This makes it possible to create a file that is of a different type than it appears to the user. For example, an executable may be created named "picture.png.exe", in which the user sees only "picture.png" and therefore assumes that this file is an image and most likely is safe, yet when opened runs the executable on the client machine.
An additional method is to generate the virus code from parts of existing operating system files by using the CRC16/CRC32 data. The initial code can be quite small (tens of bytes) and unpack a fairly large virus. This is analogous to a biological "prion" in the way it works but is vulnerable to signature based detection. This attack has not yet been seen "in the wild".
Methods to avoid detection
In order to avoid detection by users, some viruses employ different kinds of deception. Some old viruses, especially on the MS-DOS platform, make sure that the "last modified" date of a host file stays the same when the file is infected by the virus. This approach does not fool anti-virus software, however, especially those which maintain and date Cyclic redundancy checks on file changes.
Some viruses can infect files without increasing their sizes or damaging the files. They accomplish this by overwriting unused areas of executable files. These are called cavity viruses. For example, the CIH virus, or Chernobyl Virus, infects Portable Executable files. Because those files have many empty gaps, the virus, which was 1 KB in length, did not add to the size of the file.
Some viruses try to avoid detection by killing the tasks associated with antivirus software before it can detect them.
As computers and operating systems grow larger and more complex, old hiding techniques need to be updated or replaced. Defending a computer against viruses may demand that a file system migrate towards detailed and explicit permission for every kind of file access.
Avoiding bait files and other undesirable hosts
A virus needs to infect hosts in order to spread further. In some cases, it might be a bad idea to infect a host program. For example, many anti-virus programs perform an integrity check of their own code. Infecting such programs will therefore increase the likelihood that the virus is detected. For this reason, some viruses are programmed not to infect programs that are known to be part of anti-virus software. Another type of host that viruses sometimes avoid are bait files. Bait files (or goat files) are files that are specially created by anti-virus software, or by anti-virus professionals themselves, to be infected by a virus. These files can be created for various reasons, all of which are related to the detection of the virus:
Anti-virus professionals can use bait files to take a sample of a virus (i.e. a copy of a program file that is infected by the virus). It is more practical to store and exchange a small, infected bait file, than to exchange a large application program that has been infected by the virus.
Anti-virus professionals can use bait files to study the behavior of a virus and evaluate detection methods. This is especially useful when the virus is polymorphic. In this case, the virus can be made to infect a large number of bait files. The infected files can be used to test whether a virus scanner detects all versions of the virus.
Some anti-virus software employs bait files that are accessed regularly. When these files are modified, the anti-virus software warns the user that a virus is probably active on the system.
Since bait files are used to detect the virus, or to make detection possible, a virus can benefit from not infecting them. Viruses typically do this by avoiding suspicious programs, such as small program files or programs that contain certain patterns of 'garbage instructions'.
A related strategy to make baiting difficult is sparse infection. Sometimes, sparse infectors do not infect a host file that would be a suitable candidate for infection in other circumstances. For example, a virus can decide on a random basis whether to infect a file or not, or a virus can only infect host files on particular days of the week.
Stealth
Some viruses try to trick antivirus software by intercepting its requests to the operating system. A virus can hide itself by intercepting the antivirus software’s request to read the file and passing the request to the virus, instead of the OS. The virus can then return an uninfected version of the file to the antivirus software, so that it seems that the file is "clean". Modern antivirus software employs various techniques to counter stealth mechanisms of viruses. The only completely reliable method to avoid stealth is to boot from a medium that is known to be clean.
Self-modification
Most modern antivirus programs try to find virus-patterns inside ordinary programs by scanning them for so-called virus signatures. A signature is a characteristic byte-pattern that is part of a certain virus or family of viruses. If a virus scanner finds such a pattern in a file, it notifies the user that the file is infected. The user can then delete, or (in some cases) "clean" or "heal" the infected file. Some viruses employ techniques that make detection by means of signatures difficult but probably not impossible. These viruses modify their code on each infection. That is, each infected file contains a different variant of the virus.
Encryption with a variable key
A more advanced method is the use of simple encryption to encipher the virus. In this case, the virus consists of a small decrypting module and an encrypted copy of the virus code. If the virus is encrypted with a different key for each infected file, the only part of the virus that remains constant is the decrypting module, which would (for example) be appended to the end. In this case, a virus scanner cannot directly detect the virus using signatures, but it can still detect the decrypting module, which still makes indirect detection of the virus possible. Since these would be symmetric keys, stored on the infected host, it is in fact entirely possible to decrypt the final virus, but this is probably not required, since self-modifying code is such a rarity that it may be reason for virus scanners to at least flag the file as suspicious.
An old, but compact, encryption involves XORing each byte in a virus with a constant, so that the exclusive-or operation had only to be repeated for decryption. It is suspicious for a code to modify itself, so the code to do the encryption/decryption may be part of the signature in many virus definitions.
Polymorphic code
Polymorphic code was the first technique that posed a serious threat to virus scanners. Just like regular encrypted viruses, a polymorphic virus infects files with an encrypted copy of itself, which is decoded by a decryption module. In the case of polymorphic viruses, however, this decryption module is also modified on each infection. A well-written polymorphic virus therefore has no parts which remain identical between infections, making it very difficult to detect directly using signatures. Antivirus software can detect it by decrypting the viruses using an emulator, or by statistical pattern analysis of the encrypted virus body. To enable polymorphic code, the virus has to have a polymorphic engine (also called mutating engine or mutation engine) somewhere in its encrypted body. SeePolymorphic code for technical detail on how such engines operate.^[21]
Some viruses employ polymorphic code in a way that constrains the mutation rate of the virus significantly. For example, a virus can be programmed to mutate only slightly over time, or it can be programmed to refrain from mutating when it infects a file on a computer that already contains copies of the virus. The advantage of using such slow polymorphic code is that it makes it more difficult for antivirus professionals to obtain representative samples of the virus, because bait files that are infected in one run will typically contain identical or similar samples of the virus. This will make it more likely that the detection by the virus scanner will be unreliable, and that some instances of the virus may be able to avoid detection.
Metamorphic code
To avoid being detected by emulation, some viruses rewrite themselves completely each time they are to infect new executables. Viruses that utilize this technique are said to be metamorphic. To enable metamorphism, a metamorphic engine is needed. A metamorphic virus is usually very large and complex. For example, W32/Simile consisted of over 14000 lines of Assembly languagecode, 90% of which is part of the metamorphic engine.^[22]^[23]
Vulnerability and countermeasures
The vulnerability of operating systems to viruses
Just as genetic diversity in a population decreases the chance of a single disease wiping out a population, the diversity of software systems on a network similarly limits the destructive potential of viruses. This became a particular concern in the 1990s, when Microsoft gained market dominance in desktop operating systems and office suites. The users of Microsoft software (especially networking software such as Microsoft Outlook and Internet Explorer) are especially vulnerable to the spread of viruses. Microsoft software is targeted by virus writers due to their desktop dominance, and is often criticized for including many errors and holes for virus writers to exploit. Integrated and non-integrated Microsoft applications (such as Microsoft Office) and applications with scripting languages with access to the file system (for example Visual Basic Script (VBS), and applications with networking features) are also particularly vulnerable.
Although Windows is by far the most popular target operating system for virus writers, viruses also exist on other platforms. Any operating system that allows third-party programs to run can theoretically run viruses. Some operating systems are more secure than others. Unix-based operating systems (and NTFS-aware applications on Windows NT based platforms) only allow their users to run executables within their own protected memory space.
An Internet based experiment revealed that there were cases when people willingly pressed a particular button to download a virus. Security analyst Didier Stevens ran a half year advertising campaign on Google AdWords which said "Is your PC virus-free? Get it infected here!". The result was 409 clicks.^[24]^[25]
As of 2006, there are relatively few security exploits targeting Mac OS X (with a Unix-based file system and kernel).^[26] The number of viruses for the older Apple operating systems, known as Mac OS Classic, varies greatly from source to source, with Apple stating that there are only four known viruses, and independent sources stating there are as many as 63 viruses. Many Mac OS Classic viruses targeted the HyperCard authoring environment. The difference in virus vulnerability between Macs and Windows is a chief selling point, one that Apple uses in their Get a Mac advertising.^[27] In January 2009, Symantec announced the discovery of a trojan that targets Macs.^[28] This discovery did not gain much coverage until April 2009.^[28]
While Linux, and Unix in general, has always natively blocked normal users from having access to make changes to the operating system environment, Windows users are generally not. This difference has continued partly due to the widespread use of administrator accounts in contemporary versions like XP. In 1997, when a virus for Linux was released – known as "Bliss" – leading antivirus vendors issued warnings that Unix-like systems could fall prey to viruses just like Windows.^[29] The Bliss virus may be considered characteristic of viruses – as opposed to worms – on Unix systems. Bliss requires that the user run it explicitly, and it can only infect programs that the user has the access to modify. Unlike Windows users, most Unix users do not log in as an administrator user except to install or configure software; as a result, even if a user ran the virus, it could not harm their operating system. The Bliss virus never became widespread, and remains chiefly a research curiosity. Its creator later posted the source code to Usenet, allowing researchers to see how it worked.^[30]
The role of software development
Because software is often designed with security features to prevent unauthorized use of system resources, many viruses must exploit software bugs in a system or application to spread. Software development strategies that produce large numbers of bugs will generally also produce potential exploits.
How to protect your computer against viruses
To protect your computer against viruses, follow these steps:

On the computer, turn on the firewall.
Keep the computer operating system up-to-date.
Use updated antivirus software on the computer.
Use updated antispyware software on the computer.
For more information about how to protect a computer against viruses, visit the following Microsoft Web site:

http://www.microsoft.com/protect/computer/default.mspx
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How to obtain computer virus and security-related support
For United States and Canada
The computer safety team is available for computer virus and for other security-related support 24 hours a day in the United States and in Canada.   To obtain computer virus and security-related support, follow these steps:

Before you contact a support engineer, make sure that you run updated antivirus software and updated spyware removal software on the infected computer.   For more information about how to obtain a free computer safety scan, visit the following Microsoft Web site:http://onecare.live.com/site/en-us/default.htm?s_cid=sah
For more information about antispyware software, visit the following Microsoft Web site:http://www.microsoft.com/protect/computer/spyware/as.mspx
















 

Anti-virus software and other preventive measures
Many users install anti-virus software that can detect and eliminate known viruses after the computer downloads or runs the executable. There are two common methods that an anti-virus softwareapplication uses to detect viruses. The first, and by far the most common method of virus detection is using a list of virus signature definitions. This works by examining the content of the computer's memory (its RAM, and boot sectors) and the files stored on fixed or removable drives (hard drives, floppy drives), and comparing those files against a database of known virus "signatures". The disadvantage of this detection method is that users are only protected from viruses that pre-date their last virus definition update. The second method is to use a heuristic algorithm to find viruses based on common behaviors. This method has the ability to detect novel viruses that anti-virus security firms have yet to create a signature for.
Some anti-virus programs are able to scan opened files in addition to sent and received e-mails "on the fly" in a similar manner. This practice is known as "on-access scanning". Anti-virus software does not change the underlying capability of host software to transmit viruses. Users must update their software regularly to patch security holes. Anti-virus software also needs to be regularly updated in order to recognize the latest threats.
One may also minimize the damage done by viruses by making regular backups of data (and the operating systems) on different media, that are either kept unconnected to the system (most of the time), read-only or not accessible for other reasons, such as using different file systems. This way, if data is lost through a virus, one can start again using the backup (which should preferably be recent).
If a backup session on optical media like CD and DVD is closed, it becomes read-only and can no longer be affected by a virus (so long as a virus or infected file was not copied onto the CD/DVD). Likewise, an operating system on a bootable CD can be used to start the computer if the installed operating systems become unusable. Backups on removable media must be carefully inspected before restoration. The Gammima virus, for example, propagates via removable flash drives.^[31]^[32]
Recovery methods
Once a computer has been compromised by a virus, it is usually unsafe to continue using the same computer without completely reinstalling the operating system. However, there are a number of recovery options that exist after a computer has a virus. These actions depend on severity of the type of virus.
Virus removal
One possibility on Windows Me, Windows XP, Windows Vista and Windows 7 is a tool known as System Restore, which restores the registry and critical system files to a previous checkpoint. Often a virus will cause a system to hang, and a subsequent hard reboot will render a system restore point from the same day corrupt. Restore points from previous days should work provided the virus is not designed to corrupt the restore files or also exists in previous restore points.^[33] Some viruses, however, disable System Restore and other important tools such as Task Manager and Command Prompt. An example of a virus that does this is CiaDoor. However, many such viruses can be removed by rebooting the computer, entering Windows safe mode, and then using system tools.
Administrators have the option to disable such tools from limited users for various reasons (for example, to reduce potential damage from and the spread of viruses). A virus can modify the registry to do the same even if the Administrator is controlling the computer; it blocks all users including the administrator from accessing the tools. The message "Task Manager has been disabled by your administrator" may be displayed, even to the administrator.^{[citation needed]}
Users running a Microsoft operating system can access Microsoft's website to run a free scan, provided they have their 20-digit registration number. Many websites run by anti-virus softwarecompanies provide free online virus scanning, with limited cleaning facilities (the purpose of the sites is to sell anti-virus products). Some websites allow a single suspicious file to be checked by many antivirus programs in one operation.
Operating system reinstallation
Reinstalling the operating system is another approach to virus removal. It involves either reformatting the computer's hard drive and installing the OS and all programs from original media, or restoring the entire partition with a clean backup image. User data can be restored by booting from a Live CD, or putting the hard drive into another computer and booting from its operating system with great care not to infect the second computer by executing any infected programs on the original drive; and once the system has been restored precautions must be taken to avoid reinfection from a restoredexecutable file.
These methods are simple to do, may be faster than disinfecting a computer, and are guaranteed to remove any malware. If the operating system and programs must be reinstalled from scratch, the time and effort to reinstall, reconfigure, and restore user preferences must be taken into account. Restoring from an image is much faster, totally safe, and restores the exact configuration to the state it was in when the image was made, with no further trouble.
One might think of a computer virus as a tiny computer program designed to perform mischief. Most computer users have heard about computer viruses. A computer virus is the result of a destructive program that someone has written and placed inside a computer program, which unsuspecting people then place in their computer system.
Some viruses can erase all the information from the place where it's stored on the computer's hard disk. But each virus is different. Some display strange messages on your computer screen; others make small changes in your computer programs.

Where do these viruses come from? They certainly don't float around in the air like some human viruses. Instead, like any other computer program, a human must create them.

Why do people create them? It's hard to say. Some people create these programs out of meanness to get even. While others create them just as a challenge. Why do you thing people create these very destructive programs? How does your computer get a virus? Almost exactly the way humans do. The computer gets exposed to one. Well, its not quiet that easy.

Many people get contaminated computer programs by trading programs with other people. Others get contaminated computer programs through the use of modems, which allow computers to communicate over telephone lines (ie. The Internet)

Most of the time, programs that arrive by modem or a trade are perfectly safe to use. However, you do stand a chance of getting a program that has been tampered with. Here a computer program virus is hiding inside the normal program. Many computer programs that are traded were copied illegally.

When this program enters your computer through your input device, it hides in your computer's memory and starts to duplicate itself like a disease. When you save your data, you also save the virus. Slowly but surely, the virus crowds out your data and causes major system problems.

The virus can't affect the computer's ROM (Read Only Memory), but it can affect RAM (Random Access Memory) and your computer disks. When your shut off your computer a virus that has been picked up will be lost, just like any other memory that is held in RAM.

If the virus is on your disk or hard drive, it will return to the computer when you use the program again. If you switch from one program to another without shutting down the machine, the virus will attach itself to the new program. In this way, it can slowly infect all your programs before you know that it exists. Today millions of dollars are being spent to rid and protect computer systems from these virus programs.

Commercial and shareware programs have been created with the sole purpose of detecting and fixing suspect programs that might be viruses infected. These detection programs should be ran when any disk is put into your disk drive or every time your computer is first started up each day to scan the computer's hard drive.











Directions: On a separate sheet of paper, answer the following questions in your own words based on the following article you have just read.Questions:1. What is a computer virus?  2. What are some of the things that viruses can do?  3. Where do viruses come from?  4. Why do people create viruses?  5. How do computers acquire viruses?  6. Can a virus affect the ROM of a computer?  7. What can be done to avoid getting a computer virus?  8. What can be done when someone knows they have a virus?  


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