Filters are the devices that help to remove impurities from water by means of a physical separators or chemical instruments. Filters cleanse water for irrigation, drinking water, aquariums and swimming pools. They can also be bought in the shops for domestic purpose. Two major brands are PUR and Brita. These filters take away the impure contents from the water. The presence of such impure contents may cause diseases like cancer, jaundice etc and things that taste or smell bad. The composition of filters is based solely on sieving, ion exchanges and other processes.

Types of Water Filters

UV Filters:

UV Filters have the ability of killing the majority of bacteria and viruses present in the water and one, which passes through them. Chemical pollutants will not be removed from the water with UV filters. The treatment is not efficient beyond the area of treatment, so water should be used as immediate as possible after it is treated.

Sand Filters:

Sand based water filters are generally used for more than hundred years for wastewater treatment. These filters are used on a larger scale to treat a water supply for a whole community, and they are custom made. Normally any apparatus needs a constant flow of water to work properly, and hence they cannot be used for well water treatment. Recently a Canadian scientist, David Manz developed an intermittent unit. You can buy pre-built units for domestic use, which are generally used in swimming pool pumps.

Charcoal Water Filters

These are generally from coconut husk as a filter medium. This generally takes in impurities as the water passes through. This form of filter comprises possibly 95% of those in use domestically, because they are very easy to install, they are comparatively cheaper, and filter out the dreadful contaminants, Cryptosporidium and Giardia. An average charcoal filter will last a family 6-9 months. They   are also enhanced by the use of activated silver, which provides extra antibacterial power of filtering. Minerals in solution can still enrich a charcoal filter. Such Minerals improvise health.

Reverse Osmosis Water Filters

They make use of a semi-permeable membrane to filter through osmotic process. They take all the impurities out of the water, leaving it pure that is stated  installed under-sink, it needs a person   to come every few months to install a new membrane.

A supercomputer is a computer that leads the world in terms of processing capacity, particularly speed of calculation, at the time of its introduction. (The term Super Computing was first used by New York World newspaper in 1920 to refer to the large custom built tabulators IBM had made for Columbia University.)

Supercomputers introduced in the 1960s were designed primarily by Seymour Cray at Control Data Corporation (CDC), and led the market into the 1970s until Cray left to form his own company, Cray Research. He then took over the supercomputer market with his new designs, holding the top spot in supercomputing for 5 years (1985–1990). In the 1980s a large number of smaller competitors entered the market, in a parallel to the creation of the minicomputer market a decade earlier, but many of these disappeared in the mid-1990s "supercomputer market crash". Today, supercomputers are typically one-of-a-kind custom designs produced by "traditional" companies such as IBM and HP, who had purchased many of the 1980s companies to gain their experience, although Cray Inc. still specializes in building supercomputers.

The Cray-2; world's fastest computer 1985–1989.The term supercomputer itself is rather fluid, and today's supercomputer tends to become tomorrow's also-ran. CDC's early machines were simply very fast scalar processors, some ten times the speed of the fastest machines offered by other companies. In the 1970s most supercomputers were dedicated to running a vector processor, and many of the newer players developed their own such processors at lower price points to enter the market. The early and mid-1980s saw machines with a modest number of vector processors working in parallel become the standard. Typical numbers of processors were in the range 4–16. In the later 1980s and 1990s, attention turned from vector processors to massive parallel processing systems with thousands of "ordinary" CPUs; some being off the shelf units and others being custom designs. Today, parallel designs are based on "off the shelf" RISC microprocessors, such as the PowerPC or PA-RISC, and most modern supercomputers are now highly-tuned computer clusters using commodity processors combined with custom interconnects.

Contents
1 Software tools
2 Uses
3 Design
3.1 Supercomputer challenges, technologies
3.2 Processing techniques
3.3 Operating systems
3.4 Programming
4 Types of general-purpose supercomputers
5 Special-purpose supercomputers
6 The fastest supercomputers today
6.1 Measuring supercomputer speed
6.2 Current fastest supercomputer system
6.3 Previous fastest supercomputer system
6.4 Quasi-supercomputing
7 Timeline of supercomputers
8.1 General concepts, history
8.2 Other classes of computer
8.3 Supercomputer companies, operating
8.4 Supercomputer companies, defunct

Software tools
Software tools for distributed processing include standard APIs such as MPI and PVM and open source-based software solutions such as Beowulf and openMosix which facilitate the creation of a sort of "virtual supercomputer" from a collection of ordinary workstations or servers. Technology like ZeroConf (Rendezvous/Bonjour) pave the way for the creation of ad hoc computer clusters. An example of this is the distributed rendering function in Apple's Shake compositing application. Computers running the Shake software merely need to be in proximity to each other, in networking terms, to automatically discover and use each other's resources. While no one has yet built an ad hoc computer cluster that rivals even yesteryear's supercomputers, the line between desktop, or even laptop, and supercomputer is beginning to blur, and is likely to continue to blur as built-in support for parallelism and distributed processing increases in mainstream desktop operating systems. An easy programming language for supercomputers remains an open research topic in Computer Science.

Uses
Supercomputers are used for highly calculation-intensive tasks such as weather forecasting, climate research (including research into global warming), molecular modeling (computing the structures and properties of chemical compounds, biological macromolecules, polymers, and crystals), physical simulations (such as simulation of airplanes in wind tunnels, simulation of the detonation of nuclear weapons, and research into nuclear fusion), cryptanalysis, and the like. Military and scientific agencies are heavy users.

Design
Supercomputers traditionally gained their speed over conventional computers through the use of innovative designs that allow them to perform many tasks in parallel, as well as complex detail engineering. They tend to be specialized for certain types of computation, usually numerical calculations, and perform poorly at more general computing tasks. Their memory hierarchy is very carefully designed to ensure the processor is kept fed with data and instructions at all times—in fact, much of the performance difference between slower computers and supercomputers is due to the memory hierarchy design and componentry. Their I/O systems tend to be designed to support high bandwidth, with latency less of an issue, because supercomputers are not used for transaction processing.As with all highly parallel systems, Amdahl's law applies, and supercomputer designsdevote great effort to eliminating software serialization, and using hardware to accelerate the remaining bottlenecks.

Supercomputer challenges, technologies
A supercomputer generates large amounts of heat and must be cooled. Cooling most supercomputers is a major HVAC problem.
Information cannot move faster than the speed of light between two parts of a supercomputer. For this reason, a supercomputer that is many meters across must have latencies between its components measured at least in the tens of nanoseconds. Seymour Cray's supercomputer designs attempted to keep cable runs as short as possible for this reason: hence the cylindrical shape of his famous Cray range of computers.
Supercomputers consume and produce massive amounts of data in a very short period of time. According to Ken Batcher, "A supercomputer is a device for turning compute-bound problems into I/O-bound problems." Much work on external storage bandwidth is needed to ensure that this information can be transferred quickly and stored/retrieved correctly.
Technologies developed for supercomputers include:

Vector processing
Liquid cooling
Non-Uniform Memory Access (NUMA)
Striped disks (the first instance of what was later called RAID)
Parallel filesystems

Processing techniques
Vector processing techniques were first developed for supercomputers and continue to be used in specialist high-performance applications. Vector processing techniques have trickled down to the mass market in DSP architectures and SIMD processing instructions for general-purpose computers. Modern video game consoles in particular use SIMD extensively and this is the basis for some manufacturers' claim that their game machines are themselves supercomputers.

Operating systems
Supercomputer operating systems, today most often variants of UNIX, are every bit as complex as those for smaller machines, if not more so. Their user interfaces tend to be less developed however, as the OS developers have limited programming resources to spend on non-essential parts of the OS (i.e., parts not directly contributing to the optimal utilization of the machine's hardware). This stems from the fact that because these computers, often priced at millions of dollars, are sold to a very small market, their R&D budgets are often limited. Interestingly this has been a continuing trend throughout the supercomputer industry, with former technology leaders such as Silicon Graphics taking a backseat to such companies as NVIDIA, who have been able to produce cheap, feature rich, high-performance, and innovative products due to the vast number of consumers driving their R&D.

Historically, until the early-to-mid-1980s, supercomputers usually sacrificed instruction set compatibility and code portability for performance (processing and memory access speed). For the most part, supercomputers to this time (unlike high-end mainframes) had vastly different operating systems. The Cray-1 alone had at least six different proprietary OSs largely unknown to the general computing community. Similarly different and incompatible vectorizing and parallelizing compilers for Fortran existed. This trend would have continued with the ETA-10 were it not for the initial instruction set compatibility between the Cray-1 and the Cray X-MP, and the adoption of UNIX operating system variants (such as Cray's UniCOS).
For this reason, in the future, the highest performance systems are likely to have a UNIX flavor but with incompatible system unique features (especially for the highest end systems at secure facilities).

Programming
The parallel architectures of supercomputers often dictate the use of special programming techniques to exploit their speed. Special-purpose Fortran compilers can often generate faster code than the C or C++ compilers, so Fortran remains the language of choice for scientific programming, and hence for most programs run on supercomputers. To exploit the parallelism of supercomputers, programming environments such as PVM and MPI for loosely connected clusters and OpenMP for tightly coordinated shared memory machines are being used.

Types of general-purpose supercomputers
There are three main classes of general-purpose supercomputers:

Vector processing machines allow the same (arithmetical) operation to be carried out on a large amount of data simultaneously.
Tightly connected cluster computers use specially developed interconnects to have many processors and their memory communicate with each other, typically in a NUMA architecture. Processors and networking components are engineered from the ground up for the supercomputer. The fastest general-purpose supercomputers in the world today use this technology.
Commodity clusters use a large number of commodity PCs, interconnected by high-bandwidth low-latency local area networks.
As of 2002, Moore's Law and economies of scale are the dominant factors in supercomputer design: a single modern desktop PC is now more powerful than a 15-year old supercomputer, and at least some of the design tricks that allowed past supercomputers to out-perform contemporary desktop machines have now been incorporated into commodity PCs. Furthermore, the costs of chip development and production make it uneconomical to design custom chips for a small run and favor mass-produced chips that have enough demand to recoup the cost of production.

Additionally, many problems carried out by supercomputers are particularly suitable for parallelization (in essence, splitting up into smaller parts to be worked on simultaneously) and, particularly, fairly coarse-grained parallelization that limits the amount of information that needs to be transferred between independent processing units. For this reason, traditional supercomputers can be replaced, for many applications, by "clusters" of computers of standard design which can be programmed to act as one large computer.

Special-purpose supercomputers
Special-purpose supercomputers are high-performance computing devices with a hardware architecture dedicated to a single problem. This allows the use of specially programmed FPGA chips or even custom VLSI chips, allowing higher price/performance ratios by sacrificing generality. They are used for applications such as astrophysics computation and brute-force codebreaking.Examples of special-purpose supercomputers:eep Blue, for playing chess Reconfigurable computing machines or parts of machines GRAPE, for astrophysics Deep Crack, for breaking the DES cipher

The fastest supercomputers today
Measuring supercomputer speed
The speed of a supercomputer is generally measured in "FLOPS" (FLoating Point Operations Per Second); this measurement is based on a particular benchmark, which mimics a class of real-world problems, but is significantly easier to compute than a majority of actual real-world problems.

]
Current fastest supercomputer system

The IBM Blue Gene/L is the fastest supercomputer in the world.On March 25, 2005, IBM's Blue Gene/L prototype became the fastest supercomputer in a single installation using its 32,768 processors to run at 280.6 TFLOPS. The Blue Gene/L prototype is a customized version of IBM's PowerPC architecture. The prototype was developed at IBM's Rochester, Minnesota facility, but production versions were rolled out to various sites, including Lawrence Livermore National Laboratory (LLNL). On October 28, 2005 the machine reached 280.6 TFLOPS, but the LLNL system is expected to achieve at least 360 TFLOPS, and a future update will take it to 0.5 PFLOPS. Before this, a Blue Gene/L fitted with 131,072 processors managed seven hours of sustained calculating at a 101.5 teraflops—another first. [1]

The Google server farm constitutes one of the most powerful supercomputers in the world.

Previous fastest supercomputer system
Prior to Blue Gene/L, the fastest supercomputer was the NEC Earth Simulator at the Yokohama Institute for Earth Sciences, Japan. It is a cluster of 640 custom-designed 8-way vector processor computers based on the NEC SX-6 architecture (a total of 5,120 processors). It uses a customised version of the UNIX operating system.
At the time of introduction, the Earth Simulator's performance was over five times that of the previous fastest supercomputer, the cluster computer ASCI White at Lawrence Livermore National Laboratory. The Earth Simulator held the #1 position for 2½ years. Because it was largely unanticipated by the top performers at the time, its introduction spawned the term "computnik," in a reference to the Soviet Union's upstaging of the Western space program with the 1957 launch of Sputnik.

Quasi-supercomputing
Some types of large-scale distributed computing for embarrassingly parallel problems take the clustered supercomputing concept to an extreme. One such example, the SETI@home distributed computing project has an average processing power of 72.53 TFLOPS [2].On May 16, 2005, the distributed computing project Folding@home reported a processing power of 195 TFLOPS on their CPU statistics page.[3]. Still higher powers have occasionally been recorded: on February 2, 2005, 207 TFLOPS were noted as coming from Windows, Mac, and Linux clients [4].

GIMPS [5] distributed Mersenne Prime search achieves currently 18 TFLOPS.
Google's search engine system may be faster with estimated total processing power of between 126 and 316 TFLOPS. Tristan Louis estimates the systems to be composed of between 32,000 and 79,000 dual 2 GHz Xeon machines. [6] Since it would be logistically difficult to cool so many servers at one site, Google's system would presumably be another form of distributed computing project: grid computing.

Timeline of supercomputers
Historical and present:

Period Supercomputer Peak speed Location
1906–1938 Babbage Analytical Engine, Mill 0.3 OPS RW Munro, Woodford Green, Essex, England
1938–1939 Zuse Z1 0.9 FLOPS Konrad Zuse's parents' apartment, Methfeßelstraße, Berlin, Germany
1939–1941 Zuse Z2 0.9 OPS Konrad Zuse's parents' apartment, Methfeßelstraße, Berlin, Germany
1941–1942 Zuse Z3 1.4 FLOPS German Aerodynamics Research Institute (Deutsche Versuchsanstalt
für Luftfahrt) (DVL), Berlin, Germany
1942 Atanasoff Berry Computer (ABC) 30 OPS Iowa State University, Ames, Iowa
1942–1943 TRE Heath Robinson 200 OPS Bletchley Park, England
1943–1946
1948–1954 TRE Colossus 5 kOPS Bletchley Park, England
1946–1948 U. of Pennsylvania ENIAC 50 kOPS Aberdeen Proving Ground, Maryland, USA
1954–1956 IBM NORC 67 kOPS U.S. Naval Proving Ground, Dahlgren, Virginia, USA
1956–1958 MIT TX-0 83 kOPS Massachusetts Inst. of Technology, Lexington, Massachusetts, USA
1958–1960 IBM SAGE 400 kOPS 23 U.S. Air Force sites in North America
1960–1961 UNIVAC LARC 500 kFLOPS Lawrence Livermore National Laboratory, California, USA
1961–1964 IBM 7030 "Stretch" 1.2 MFLOPS Los Alamos National Laboratory, New Mexico, USA
1964–1969 CDC 6600 3 MFLOPS Lawrence Livermore National Laboratory, California, USA
1969–1974 CDC 7600 36 MFLOPS Lawrence Livermore National Laboratory, California, USA
1974–1975 CDC Star-100 100 MFLOPS Lawrence Livermore National Laboratory, California, USA
1975–1976 Burroughs ILLIAC IV 150 MFLOPS NASA Ames Research Center, California, USA
1976–1981 Cray-1 250 MFLOPS Los Alamos National Laboratory, New Mexico, USA (80+ sold worldwide)
1981–1983 CDC Cyber 205 400 MFLOPS (numerous sites worldwide)
1983–1984 Cray X-MP/4 941 MFLOPS Los Alamos Nat. Lab.; Lawrence Livermore Nat. Lab.; Battelle; Boeing
1984–1985 M-13 2.4 GFLOPS Scientific Research Institute of Computer Complexes, Moscow, USSR
1985–1989 Cray-2/8 3.9 GFLOPS Lawrence Livermore National Laboratory, California, USA
1989–1993 ETA10-G/8 10.3 GFLOPS Florida State University, Florida, USA
1993–1994 Thinking Machines CM-5 37.5 GFLOPS Los Alamos National Laboratory, California, USA
1994–1995 Fujitsu Numerical Wind Tunnel II 236 GFLOPS National Aerospace Lab, Japan
1995–2000 Intel ASCI Red 2.15 TFLOPS Sandia National Laboratories, New Mexico, USA
2000–2002 IBM ASCI White 9.216 TFLOPS Lawrence Livermore National Laboratory, California, USA
2002–2004 NEC Earth Simulator 35.86 TFLOPS Yokohama Institute for Earth Sciences, Japan
2004–2005 IBM Blue Gene/L prototype 135.5 TFLOPS IBM, Rochester, Minnesota, USA
2005–present IBM Blue Gene/L 280.6 TFLOPS Lawrence Livermore National Laboratory, California, USA

Originally, a "computer" (sometimes spelled "computor") was a person who performed numerical calculations under the direction of a mathematician, often with the aid of a variety of mechanical calculating devices from the abacus onward. An example of an early computing device was the Antikythera mechanism, an ancient Greek device for calculating the movements of planets, dating from about 87 BC. The technology responsible for this mysterious device seems to have been lost at some point.

The end of the Middle Ages saw a reinvigoration of European mathematics and engineering, and by the early 17th century a succession of mechanical calculating devices had been constructed using clockwork technology. A considerable number of technologies that would later prove vital for the digital computer were developed in the 19th and early 20th centuries, such as the punched card, and the valve, known in America as the vacuum tube. In the 19th century, Charles Babbage was the first to conceptualise and design a fully programmable computer as early as 1837, but due to a combination of the limits of the technology of the time, limited finance, and an inability to resist tinkering with his design (a trait that would in time doom thousands of computer-related engineering projects), the device was never actually constructed in his time.During the first half of the 20th century, many scientific computing needs were met by some increasingly sophisticated, special purpose analog computers, which used a direct physical or electrical model of the problem as a basis for computation. These became increasingly rare after the development of the digital computer.

A succession of steadily more powerful and flexible computing devices were constructed in the 1930s and 1940s, gradually adding the key features of modern computers: the use of digital electronics (essentially invented by Claude Shannon in 1937), and more flexible programmability. Defining one point along this road as "the first computer" is exceedingly difficult. Notable achievements include the Atanasoff Berry Computer, a special-purpose machine that used valve-driven computation and binary numbers; Konrad Zuse's Z machines; the electro-mechanical Z3 was arguably the first universal computer, but it was completely impractical to use in this manner; the American ENIAC — a general purpose machine, but with an inflexible architecture that meant reprogramming it essentially required it to be rewired; and the secret British Colossus computer, which had limited programmability but demonstrated that a device using thousands of valves could be made reliable and reprogrammed electronically.

The team who developed ENIAC, recognizing its flaws, came up with a far more flexible and elegant design which has become known as the stored program architecture, which is the basis from which virtually all modern computers were derived. A number of projects to develop computers based on the stored program architecture commenced in the late 1940s; the first of these to be up and running was the Manchester Small-Scale Experimental Machine, but the EDSAC was perhaps the first practical version.

Valve-driven computers design were used throughout the 1950s, but were eventually replaced with transistor-based computers in the 1960s, which were smaller, faster, cheaper, and much more reliable, and thus smaller, faster, and cheaper computers became available commercially. By the 1970s, the adoption of integrated circuit technology had enabled computers to be produced at a low enough cost to allow individuals to own a personal computer of the type familiar today.

How computers work: the stored program architecture
While the technologies used in computers have changed dramatically since the first electronic, general-purpose, computers of the 1940s, most still use the stored program architecture (sometimes called the von Neumann architecture; as the article describes the primary inventors were probably ENIAC designers J. Presper Eckert and John William Mauchly). The design made the universal computer a practical reality.
The architecture describes a computer with four main sections: the arithmetic and logic unit (ALU), the control circuitry, the memory, and the input and output devices (collectively termed I/O). These parts are interconnected by a bundle of wires (a "bus") and are usually driven by a timer or clock (although other events could drive the control circuitry).

Conceptually, a computer's memory can be viewed as a list of cells (see block). Each cell has a numbered "address" and can store a small, fixed amount of information. This information can either be an instruction, telling the computer what to do, or data, the information which the computer is to process using the instructions that have been placed in the memory. In principle, any cell can be used to store either instructions or dataThe ALU is in many senses the heart of the computer. It is capable of performing two classes of basic operations: arithmetic operations, the core of which is the ability to add or subtract two numbers but also encompasses operations like "multiply this number by 2" or "divide by 2" (for reasons which will become clear later), as well as some others. The second class of ALU operations involves comparison operations, which, given two numbers, can determine if they are equal, and if not, which is bigger.

The I/O systems are the means by which the computer receives information from the outside world, and reports its results back to that world. On a typical personal computer, input devices include objects like the keyboard and mouse, and output devices include computer monitors, printers and the like, but as will be discussed later a huge variety of devices can be connected to a computer and serve as I/O devices.The control system ties this all together. Its job is to read instructions and data from memory or the I/O devices, decode the instructions, providing the ALU with the correct inputs according to the instructions, "tell" the ALU what operation to perform on those inputs, and send the results back to the memory or to the I/O devices. One key component of the control system is a counter that keeps track of what the address of the current instruction is; typically this is incremented each time an instruction is executed, unless the instruction itself indicates that the next instruction should be at some other location (allowing the computer to repeatedly execute the same instructions). Physically, since the 1980s the ALU and control unit have been located on a single integrated circuit called a Central Processing Unit or CPU.

The functioning of such a computer is in principle quite straightforward. Typically, on each clock cycle, the computer fetches instructions and data from its memory. The instructions are executed, the results are stored, and the next instruction is fetched. This procedure repeats until a halt instruction is encountered.

Larger computers, such as some minicomputers, mainframe computers, servers, differ from the model above in one significant aspect; rather than one CPU they often have a number of them. Supercomputers often have highly unusual architectures significantly different from the basic stored-program architecture, sometimes featuring thousands of CPUs, but such designs tend to be useful only for specialised tasks.

Digital circuits
The conceptual design above could be implemented using a variety of different technologies. As previously mentioned, a stored program computer could be designed entirely of mechanical components like Babbage's. However, digital circuits allow Boolean logic and arithmetic using binary numerals to be implemented using relays - essentially, electrically controlled switches. Shannon's famous thesis showed how relays could be arranged to form units called logic gates, implementing simple Boolean operations. Others soon figured out the vacuum tubes - electronic devices, could be used instead. Vacuum tubes were originally used as a signal amplifier for radio and other applications, but were used in digital electronics as a very fast switch; when electricity is provided to one of the pins, current can flow through between the other two.

Through arrangements of logic gates, one can build digital circuits to do more complex tasks, for instance, an adder, which implements in electronics the same method - in computer terminology, an algorithm - to add two numbers together that children are taught - add one column at a time, and carry what's left over. Eventually, through combining circuits together, a complete ALU and control system can be built up. This does require a considerable number of components. CSIRAC, one of the earliest stored-program computers, is probably close to the smallest practically useful design. It had about 2,000 valves, Some of which were "dual components", so this represented somewhere between 2 and 4,000 logic components.

Vacuum tubes had severe limitations for the construction of large numbers of gates. They were expensive, unreliable (particularly when used in such large quantities), took up a lot of space, and used a lot of electrical power, and, while incredibly fast compared to a mechanical switch, had limits to the speed at which they could operate. Therefore, by the 1960s they were replaced by the transistor, a new device which performed the same task as the tube but was much smaller, faster operating, reliable, used much less power, and was far cheaper.

Integrated circuits are the basis of modern digital computing hardware.In the 1960s and 1970s, the transistor itself was gradually replaced by the integrated circuit, which placed multiple transistors (and other components) and the wires connecting them on a single, solid piece of silicon. By the 1970s, the entire ALU and control unit, the combination becoming known as a CPU, were being placed on a single "chip" called a microprocessor. Over the history of the integrated circuit, the number of components that can be placed on one has grown enormously. The first IC's contained a few tens of components; as of 2005, modern microprocessors such from AMD and Intel contain over 100 million transistors.

Tubes, transistors, and transistors on integrated circuits can be and are used as the "storage" component of the stored-program architecture, using a circuit design known as a flip-flop, and indeed flip-flops are used for small amounts of very high-speed storage. However, few computer designs have used flip-flops for the bulk of their storage needs. Instead, earliest computers stored data in Williams tubes - essentially, projecting some dots on a TV screen and reading them again, or mercury delay lines where the data was stored as sound pulses travelling slowly (compared to the machine itself) along long tubes filled with mercury. These somewhat ungainly but effective methods were eventually replaced by magnetic memory devices, such as magnetic core memory, where electrical currents were used to introduce a permanent (but weak) magnetic field in some ferrous material, which could then be read to retrieve the data. Eventually, DRAM was introduced. A DRAM unit is a type of integrated circuit containing huge banks of an electronic component called a capacitor which can store an electrical charge for a period of time. The level of charge in a capacitor could be set to store information, and then measured to read the information when required.

I/O devices
I/O is a general term for the devices by which a computer is sent information from the outside world, including instructions on what it is to do, and how it sends back the results of its computations; these can either be for the purpose of viewing by people, or perhaps for the purposes of controlling other machines; in a robot, for instance, the controlling computer's major output device is the robot itself.

The first generation of computers were typically equipped with a fairly limited range of input devices; a punch card reader or something similar was used to input instructions and data into the computers memory, and some kind of printer, usually a modified teletype, was used to record the results. Over the years, though, a huge variety of other devices have been added. For the personal computer, for instance, Keyboards, and mice, are the primary ways people directly enter information into the computer, and monitors are a major way information from the computer is presented back to the computer user, though printers and some kind of sound-generating device are also very commonly used. There are a huge variety of other devices for obtaining other types of input; one example is the digital camera, which can be used to input visual information. Two of the most prominent classes of I/O device are secondary storage devices such as hard disks, CD-ROMs, key drives and the like; these represent comparatively slow, but high-capacity devices where information can be stored for later retrieval. Second is devices to access computer networks; the ability to transfer data between computers has opened up a huge range of capabilities for the computer. Collectively, the global Internet lets millions of computers transfer information of all types between each other.

Instructions
The instructions interpreted by the control unit, and executed by the ALU, are not nearly as rich as a human language. A computer only has a limited number of well-defined, simple instructions, but they are not ambiguous. Typical sorts of instructions supported by most computers are "copy the contents of memory cell 5 and place the copy in cell 10", "add the contents of cell 7 to the contents of cell 13 and place the result in cell 20", "if the contents of cell 999 are 0, the next instruction is at cell 30". All computer instructions fall into one of four categories: 1) moving data from one location to another; 2) executing arithmetic and logical processes on data; 3) testing the condition of data; and 4) altering the sequence of operations.

Instructions are represented within the computer as binary code - a base two system of counting. For example, the code for one kind of "copy" operation in the Intel line of microprocessors is 10110000. The particular instruction set that a specific computer supports is known as that computer's machine language.To slightly oversimplify, if two computers have CPUs share the same set of instructions, software from one can run on the other without modification. This easy portability of existing software creates a great incentive to stick with existing designs, only switching for the most compelling of reasons, and has gradually narrowed the number of distinct instruction set architectures in the marketplace.

Programs
Computer programs are simply lists of instructions for the computer to execute. This can range from just a few instructions which perform a simple task, to a much more complex instruction list which may also include tables of data. Many computer programs contain millions of instructions, and many of those instructions are executed repeatedly. A typical modern PC (in the year 2005) can execute around 3 billion instructions per second. Computers do not gain their extraordinary capabilities through the ability to execute complex instructions. Rather, they do millions of simple instructions arranged by people known as "programmers."

In practice, people do not normally write the instructions for computers directly in machine language. Such programming is incredibly tedious and highly error-prone, making programmers very unproductive. Instead, programmers describe the desired actions in a "high level" programming language which is then translated into the machine language automatically by special computer programs (interpreters and compilers). Some programming languages map very closely to the machine language, such as Assembly Language (low level languages); at the other end, languages like Prolog are based on abstract principles far removed from the details of the machine's actual operation (high level languages). The language chosen for a particular task depends on the nature of the task, the skillset of the programmers, tool availability and, often, the requirements of the customers (for instance, projects for the US military were often required to be in the Ada programming language).

Computer software is an alternative term for computer programs; it is a more inclusive phrase and includes all the ancillary material accompanying the program needed to do useful tasks. For instance, a video game includes not only the program itself, but data representing the pictures, sounds, and other material needed to create the virtual environment of the game. A computer application is a piece of computer software provided to many computer users, often in a retail environment. The stereotypical modern example of an application is perhaps the office suite, a set of interrelated programs for performing common office tasks.

Going from the extremely simple capabilities of a single machine language instruction to the myriad capabilities of application programs means that many computer programs are extremely large and complex. A typical example is the Firefox web browser, created from roughly 2 million lines of computer code in the C++ programming language; there are many projects of even bigger scope, built by large teams of programmers. The management of this enormous complexity is key to making such projects possible; programming languages, and programming practices, enable the task to be divided into smaller and smaller subtasks until they come within the capabilities of a single programmer in a reasonable period.Nevertheless, the process of developing software remains slow, unpredictable, and error-prone; the discipline of software engineering has attempted, with some partial success, to make the process quicker and more productive and improve the quality of the end product.

Libraries and operating systems
Soon after the development of the computer, it was discovered that certain tasks were required in many different programs; an early example was computing some of the standard mathematical functions. For the purposes of efficiency, standard versions of these were collected in libraries and made available to all who required them. A particularly common task set related to handling the gritty details of "talking" to the various I/O devices, so libraries for these were quickly developed.By the 1960s, with computers in wide industrial use for many purposes, it became common for them to be used for many different jobs within an organization. Soon, special software to automate the scheduling and execution of these many jobs became available. The combination of managing "hardware" and scheduling jobs became known as the "operating system"; the classic example of this type of early operating system was OS/360 by IBM.

The next major development in operating systems was timesharing - the idea that multiple users could use the machine "simultaneously" by keeping all of their programs in memory, executing each user's program for a short time so as to provide the illusion that each user had their own computer. Such a development required the operating system to provide each user's programs with a "virtual machine" such that one user's program could not interfere with another's (by accident or design). The range of devices that operating systems had to manage also expanded; a notable one was hard disks; the idea of individual "files" and a hierachical structure of "directories" (now often called folders) greatly simplified the use of these devices for permanent storage. Security access controls, allowing computer users access only to files, directories and programs they had permissions to use, were also common.

Perhaps the last major addition to the operating system were tools to provide programs with a standardised graphical user interface. While there are few technical reasons why a GUI has to be tied to the rest of an operating system, it allows the operating system vendor to encourage all the software for their operating system to have a similar looking and acting interface.Outside these "core" functions, operating systems are usually shipped with an array of other tools, some of which may have little connection with these original core functions but have been found useful by enough customers for a provider to include them. For instance, Apple's Mac OS X ships with a digital video editor application.Not all operating systems provide all of the above functions; operating systems for smaller computers typically provide fewer, such as the highly minimal operating systems for early microcomputers. Embedded computers may have a specialised operating system, or sometimes none at all. Instead the custom programs written for their task perform all necessary functions that would be performed by an operating system in less specialised roles.

Computer applications

Computer-controlled robots are ubiquitous in industrial manufacture.The first electronic digital computers, with their large size and cost, mainly performed scientific calculations, often to support military objectives. The ENIAC was originally designed to calculate ballistics firing tables for artillery, but it was also used to calculate neutron cross-sectional densities to help in the design of the hydrogen bomb. This calculation, performed in December, 1945 through January, 1946 and involving over a million punch cards of data, showed the design then under consideration would fail. (Many of the most powerful supercomputers available today are also used for nuclear weapons simulations.) The CSIR Mk I, the first Australian stored-program computer, evaluated rainfall patterns for the catchment area of the Snowy Mountains Scheme, a large hydroelectric generation project. Others were used in cryptanalysis, for example the first programmable (though not general-purpose) digital electronic computer, Colossus, built in 1943 during World War II. Despite this early focus of scientific and military engineering applications, computers were quickly used in other areas.

From the beginning, stored program computers were applied to business problems. The LEO, a stored program-computer built by J. Lyons and Co. in the United Kingdom, was operational and being used for inventory management and other purposes 3 years before IBM built their first commercial stored-program computer. Continual reductions in the cost and size of computers saw them adopted by ever-smaller organizations. And with the invention of the microprocessor in the 1970s, it became possible to produce inexpensive computers. In the 1980s, personal computers became popular for many tasks, including book-keeping, writing and printing documents, calculating forecasts and other repetitive mathematical tasks involving spreadsheets.

Today, computer-generated imagery (CGI) is a central ingredient in motion picture visual effects. The seawater creature in The Abyss (1989) marked the acceptance of CGI in the visual effects industry.As computers have become cheaper, they have been used extensively in the creative arts as well. Sound, still pictures, and video are now routinely created (through synthesizers, computer graphics and computer animation), and near-universally edited by computer. They have also been used for entertainment, with the video game becoming a huge industry.Computers have been used to control mechanical devices since they became small and cheap enough to do so; indeed, a major spur for integrated circuit technology was building a computer small enough to guide the Apollo missions and the Minuteman missile, two of the first major applications for embedded computers. Today, it is almost rarer to find a powered mechanical device not controlled by a computer than to find one that is at least partly so. Perhaps the most famous computer-controlled mechanical devices are robots, machines with more-or-less human appearance and some subset of their capabilities. Industrial robots have become commonplace in mass production, but general-purpose human-like robots have not lived up to the promise of their fictional counterparts and remain either toys or research projects.

Robotics, indeed, is the physical expression of the field of artificial intelligence, a discipline whose exact boundaries are fuzzy but to some degree involves attempting to give computers capabilities that they do not currently possess but humans do. Over the years, methods have been developed to allow computers to do things previously regarded as the exclusive domain of humans - for instance, "read" handwriting, play chess, or perform symbolic integration. However, progress on creating a computer that exhibits "general" intelligence comparable to a human has been extremely slow.

Networking and the Internet
In the 1970s, computer engineers at research institutions throughout the US began to link their computers together using telecommunications technology. This effort was funded by ARPA, and the computer network that it produced was called the ARPANET. The technologies that made the Arpanet possible spread and evolved. In time, the network spread beyond academic institutions and became known as the Internet. The emergence of networking involved a redefinition of the nature and boundaries of the computer. In the phrase of John Gage and Bill Joy (of Sun Microsystems), "the network is the computer". That is, computer operating systems and applications were modified to include the ability to define and access the resources of other computers on the network, such as peripheral devices, stored information, and the like, as extensions of the resources of an individual computer. Initially these facilities were available primarily to people working in high-tech environments, but in the 1990s the spread of applications like email and the World Wide Web, combined with the development of cheap, fast networking technologies like Ethernet (on two local scales) and ADSL saw computer networking become ubiquitous in the developed world.

Computing professions and disciplines
In the developed world at least, there is scarcely a profession that does not make use of computers. However, certain professional and academic disciplines have evolved that specialise in techniques to construct, program, and use computers. Terminology for different professional disciplines is still somewhat fluid and new fields emerge from time to time: however, some of the major groupings are as follows:

Computer engineering is that branch of electronic engineering devoted to the physical construction of computers and their attendant components.
Computer science is an academic study of the processes related to computation, such as developing efficient algorithms to perform specific tasks. It has tackled questions as to whether problems can be solved at all using a computer, how efficiently they can be solved, and how to construct efficient programs to compute solutions. A huge array of specialities has developed within computer science to investigate different classes of problem.
Software engineering concentrates on methodologies and practices to allow the development of reliable software systems while minimising, and reliably estimating, costs and timelines.
Information systems concentrates on the use and deployment of computer systems in a wider organizational (usually business) context.
A huge number of disciplines have developed at the intersection of computers with other professions; one of many examples is experts in geographical information systems who apply computer technology to problems of managing geographical information.

Film speed is the measure of a photographic film stock's sensitivity to light. Stock with lower sensitivity requires a longer exposure and is thus called a slow film, while stock with higher sensitivity can shoot the same scene with a shorter exposure and is called a fast film.

The standard known as ISO 5800:1987 from the International Organization for Standardization (ISO) defines both a linear scale and a logarithmic scale for measuring film speed.

In the ISO linear scale, which corresponds to the older ASA scale, doubling the speed of a film (that is, halving the amount of light that is necessary to expose the film) implies doubling the numeric value that designates the film speed. In the ISO logarithmic scale, which corresponds to the older DIN scale, doubling the speed of a film implies adding 3° to the numeric value that designates the film speed. For example, a film rated ISO 200/24° is twice as sensitive as a film rated ISO 100/21°.

The most common ISO film ratings are 25/15°, 50/18°, 100/21°, 200/24°, 400/27°, 800/30°, 1600/33°, and 3200/36°. Consumer films are generally rated between 100/21° and 800/30°, inclusive.

Photographic film a sheet of plastic (polyester, celluloid (nitrocellulose) or cellulose acetate) coated with an emulsion containing light-sensitive silver halide salts (bonded by gelatin) with variable crystal sizes that determine the sensitivity and resolution of the film. When the emulsion is subjected to controlled exposure to light (or other forms of electromagnetic radiation such as X-rays), it forms a latent (invisible) image. Chemical processes can then be applied to the film to create a visible image, in a process called film developing.

In black-and-white photographic film there is usually one layer of silver salts. When the exposed grains are developed, the silver salts are converted to metallic silver, which block light and appear as the black part of the film negative.

Color film uses at least three layers. Dyes added to the silver salts make the crystals sensitive to different colors. Typically the blue-sensitive layer is on top, followed by the green and red layers. During development, the silver salts are converted to metallic silver, as with black and white film. The by-products of this reaction form colored dyes. The silver is converted back to silver salts in the bleach step of development. It is removed from the film in the fix step. Some films, like Kodacolor II, have as many as 12 emulsion layers, with upwards of 20 different chemicals in each layer.

Mechanisms for producing artificially created, two-dimensional images in motion were demonstrated as early as the 1860's, including the zoetrope and the praxinoscope. These machines were outgrowths of simple optical devices (such as magic lanterns), and would display sequences of still pictures at sufficient speed for the images on the pictures to appear to be moving. Naturally, the images needed to be carefully designed to achieve the desired effect — and the underlying principle became the basis for the development of animation.

With the development of celluloid film for still photography, it became possible to directly capture objects in motion in real time using the new medium. Early versions of the technology sometimes required the viewer to look into a special device to see the pictures. By the 1880's, the development of the motion picture camera allowed the individual component images to be captured and stored on a single reel, and led quickly to the development of a motion picture projector to shine light through the processed and printed film and magnify these "moving picture shows" onto a screen for an entire audience. These reels, so exhibited, came to be known as "motion pictures".

Motion pictures were purely visual art up to the late 1920s, but these innovative silent films had gained a hold on the public imagination. When films began to tell stories, instead of just record brief events, exhibitors sometimes provided a commentator to narrate the action, but this became unnecessary with the development of printed intertitles containing the actors' dialogue and other written, descriptive material as part of the visual experience. Rather than leave the audience in silence, theater owners would hire a pianist or organist or a full orchestra to play music fitting the mood of the film at any given moment. By the early 1920s, most films came with a prepared list of sheet music for this purposes, with complete film scores being composed for major productions.

In 1922, new technology allowed filmmakers to attach to each film a soundtrack of speech, music and sound effects synchronized with the action on the screen. These sound films were initially distinguished by calling them "talking pictures", or talkies.

The next major step in the development of cinema was the introduction of color. While the addition of sound quickly eclipsed silent film and theater musicians, color was adopted more gradually. The public was relatively indifferent to color photography as opposed to black-and-white. But as color processes improved and became as affordable as black-and-white film, more and more movies were filmed in color after the end of WWII, as the industry in America came to view color an essential to attracting audiences in its competition with television, which remained a black-and-white medium until the mid-60s. By the end of the 1960s, color had become the norm for film makers, and by the 1980s, an expectation of the younger generations by then comprising the majority of the audience for commercial films. Only in rare exceptions is black-and-white film now used; the choice is motivated by artistic reasons. Film presented today in black-and-white, like the recent release Sin City, tends to have a greater dramatic tone and can be an inspired throwback to older cinema.

A mouse is a mammal that belongs to one of numerous species of small rodents in the genus Mus and various related genera of the family Muridæ (Old World Mice).

The best known mouse species is the common house mouse (Mus musculus). It is found in nearly all countries and, as the laboratory mouse, serves as an important model organism in biology; it is also a popular pet. (Non-biologists often use the term "mouse" synonymously with "Mus musculus"). The American white-footed mouse (Peromyscus leucopus) and the deer mouse (Peromyscus maniculatus) also sometimes live in houses. These species of mice live commensally with humans. Although they may live up to two years in the lab, the average mouse in the wild lives only 3 months, primarily due to heavy predation.

Mice are very common experimental animals in biology and psychology primarily because they are mammals, and thus share a high degree of homology with humans, but can be manipulated in ways that would be considered unethical to do with humans. Additional benefits include the fact that mice are small, relatively inexpensive, and several generations can be observed in a short period of time. The mouse genome has been sequenced, and many genes which share homology to human genes have been identified. In the 2006 Biosatellite project, a group of mice will orbit Earth inside a spinning spacecraft to determine how mice react to gravity equivalent to that of Mars.

However, mice can also be harmful pests, damaging and eating crops and spreading diseases through their parasites and feces. The domestication of cats is thought to have been for their predation of mice and their relatives, the rats. A mouse trap can also be used to catch mice.

Mice generally live on a herbivore diet, but are actually omnivores: they will eat meat, the dead bodies of other mice, and have been observed to cannibalise their tails during starvation.

An estimated half million mice live on the London Underground, mostly running around the tracks.

Mice cannot see colors, but they can see the difference between colors, because they see things in shade from black to white.

A monkey is any member of two of the three groupings of simian primates. These two groupings are the New World and Old World monkeys of which together there are nearly 200 species. Because of their similarity to monkeys, apes such as chimpanzees and gibbons are sometimes incorrectly called monkeys. Also, a few monkey species have the word "ape" in their common name. Because they are not a single coherent group, monkeys do not have any important characteristics that they all share and are not shared with the remaining group of simians, the apes.

Monkeys range in size from the Pygmy Marmoset, at 10 cm (4 inch) long (plus tail) and 120 g (4 oz) in weight to the male Mandrill, almost 1 metre (3 ft) long and weighing 35 kg (75 lb). Some are arboreal (living in trees), some live on the savanna; diets differ among the various species but may contain any of the following: fruit, leaves, seeds, nuts, flowers, insects, spiders, eggs and small animals.

Some characteristics are shared among the groups; most New World monkeys have prehensile tails while Old World monkeys do not; some have trichromatic colour vision like that of humans, others are dichromats or monochromats. Although both the Wew and Old World monkeys, like the apes, have forward facing eyes, the faces of Old World and New World monkeys look very different though again, each group shares some features such as the types of noses, cheeks and rumps. To understand the monkeys, therefore, it is necessary to study the characteristics of the different groups individually.

Human beings define themselves in biological, social, and spiritual terms. Biologically, humans are classified as the species Homo sapiens (Latin for "wise man" or "clever human"): a bipedal primate belonging to the superfamily of Hominoidea, with all of the other apes: chimpanzees, bonobos, gorillas, orangutans, and gibbons.

Humans have an erect body carriage that frees the upper limbs for manipulating objects, a highly developed brain and consequent capacity for abstract reasoning, speech, language, and introspection. One current hypothesis within the scientific community is that the human evolution of bipedalism (two-legged locomotion) occurred in response to a need for long-distance running. Humans are said to be one of a short list of animals with such a capacity. Another theory is that this allowed human predecessors to see above the tall grasses of the African plains.

The human mind has several distinct attributes. It is responsible for the complexity of human behaviour, especially language. Curiosity and observation have led to a variety of explanations for consciousness and the relation between mind and body. Psychology, especially neuropsychology, attempts to study them from the scientific point of view. Religious perspectives generally emphasise a soul, qi or atman as the essence of being, and are often characterised by the belief in and worship of God, gods or spirits. Philosophy, especially philosophy of mind, attempts to fathom the depths of each of these perspectives. Art, music and literature are often used in expressing these concepts and feelings.

Humans are inherently social. Humans create complex social structures composed of many co-operating and competing groups. These range from nations and states down to families, and also from the community to the self. Seeking to understand and manipulate the world around us led to the development of technology and science as a social, rather than an individual, enterprise. These institutions have given rise to shared artefacts, beliefs, myths, rituals, values, and social norms which form the group's culture.

Iptelecoms, the UK distributors for Swyx and specialists in the distribution of IP telephony products, found they had a major success on their hands when exhibiting at the 2005 Convergence Summit held at Stoneley Park near Coventry on the 6th and 7th of August this year.

Steve Curtis, Managing Director of Iptelecoms Ltd said “The exhibition has been a major success story for us. This is the first time that we have exhibited at the Convergence Summit and we are delighted with the astounding interest shown in our product line-up.” He also told us “Over the past few weeks we have seen a major upturn in business and the time is most definitely now for IP telephony and converged solutions. Resellers are realizing that this is the only route forward and the move to IP opens up many additional revenue streams to them.”

On several occasions dealers were waiting in line for a live Swyx demonstration whilst many other stands were visibly quieter.

 Iptelecoms work closely with their reseller channel to ensure they fully understand the feature rich products that they are taking to market. 

 Mark Russell, Technical Director at Iptelecoms who has over 6 years experience with Swyx SoftPBX told us “Watching the expressions on peoples face turn into a booming smile as they were shown the feature rich product was amazing. I’ve never experienced anything quite like it. Having been in the telecoms industry for over 20 years and worked with the data industry for over 8 years we are ideally placed to both help our voice resellers understand the issues associated with entering the world of converged networks and our data resellers how the product should be taken to market.”
 
Those resellers wishing to partner with Iptelecoms should either obtain further information from http://www.iptelecoms.com or email sales@iptelecoms.com.