Donwload :  Click Here

The explosion in the use of computers began with “third-generation” computers, making use of Jack St. Clair Kilby’s and Robert Noyce’s independent invention of the integrated circuit (or microchip). This led to the invention of the microprocessor. While the subject of exactly which device was the first microprocessor is contentious, partly due to lack of agreement on the exact definition of the term “microprocessor”, it is largely undisputed that the first single-chip microprocessor was the Intel 4004, [134] designed and realized by Ted Hoff, Federico Faggin, and Stanley Mazor at Intel. [135]

While the earliest microprocessor ICs literally contained only the processor, i.e. The central processing unit, of a computer, their progressive development naturally led to chips containing most or all of the internal electronic parts of a computer. The integrated circuit and the image on the right, for example, an Intel 8742, is an 8-bit microcontroller that includes a CPU running at 12 MHz, 128 bytes of RAM, 2048 bytes of EPROM, and I / O in the same chip .

During the 1960s there was considerable overlap between second and third generation technologies. [136] IBM implemented its IBM Solid Logic Technology modules in hybrid circuits for the IBM System / 360 and 1964. As late as 1975, Sperry Univac continued the manufacture of second-generation machines such as the UNIVAC 494. The Burroughs large systems such as the B5000 were stack machines, which allowed for simpler programming. These pushdown automatons were also implemented in minicomputers and microprocessors later, which influenced programming language design. Minicomputers served as low-cost computer centers for industry, business and universities. [137] It became possible to simulate analog circuits with the simulation program with integrated circuit emphasis, or SPICE (1971) on minicomputers, one of the programs for electronic design automation (EDA). The microprocessor led to the development of the microcomputer, small, low-cost computers that could be owned by individuals and small businesses. Microcomputers, the first of which appeared in the 1970s, became ubiquitous in the 1980s and beyond.

While specific system which is considered the first microcomputer is a matter of debate, and there were several unique hobbyist developed systems based on the Intel 4004 and its successor, the Intel 8008, the first commercially available microcomputer kit was the Intel 8080-based Altair 8800 , which was announced in the January 1975 cover of Popular Electronics article. However, this was an extremely limited system in its initial stages, having only 256 bytes of DRAM and its initial package and no input-output except its toggle switches and LED display register. Despite this, it was initially surprisingly popular, with several hundred sales in the first year, and demand rapidly outstripped supply. Several early third-party vendors such as Cromemco and Processor Technology soon began supplying additional S-100 bus hardware for the Altair 8800 now.

In April 1975 at the Hannover Fair, Olivetti presented the P6060, the world’s first complete, pre-assembled personal computer system. The central processing unit consisted of two cards, code named PUCE1 and PUCE2, and unlike most other personal computers was built with TTL components rather than a microprocessor. It had one or two 8 “floppy disk drives, a 32-character plasma display, 80-column graphical thermal printer, 48 Kbytes of RAM, and the BASIC language. It weighed 40 kg (88 lb). As a complete system, this was a significant step from the Altair, though it never achieved the same success. It was in competition with a similar product by IBM that had an external floppy disk drive.

From 1975 to 1977, most microcomputers, such as the MOS Technology KIM-1, the Altair 8800, and some versions of the Apple I, were sold as kits for do-it-yourselfers. Pre-assembled systems did not gain much ground until 1977, with the introduction of the Apple II, the Tandy TRS-80 and the Commodore PET. Computing has evolved with microcomputer architectures, with features added from their larger brethren, now dominant in most market segments.

A NeXT Computer and its object-oriented development tools and libraries were used by Tim Berners-Lee and Robert Cailliau at CERN to develop the world’s first web server software, CERN httpd, and also used to write the first web browser, WorldWideWeb. These facts, along with the close association with Steve Jobs, secure the 68030 NeXT a place in history as one of the most significant computers of all time. [Citation needed]

Systems as complicated as computers require very high reliability. ENIAC remained on, in continuous operation from 1947 to 1955, for eight years before being shut down. Although a vacuum tube might fail, it would be replaced without bringing down the system. By the simple strategy of never shutting down ENIAC, the failures were dramatically reduced. The vacuum-tube SAGE air-defense computers became remarkably reliable – installed in pairs, one off-line, tubes likely to fail did as when the computer was intentionally run at reduced power to find them. Hot-pluggable hard disks, like the hot-pluggable vacuum tubes of yesteryear, continue the tradition of repair during continuous operation. Semiconductor memories routinely have no errors when they operate, although operating systems like Unix have employed memory tests on start-up to detect failing hardware. Today, the requirement of reliable performance is made even more stringent when server farms are the delivery platform. [138] Google has managed this by using fault-tolerant software to recover from hardware failures, and is even Monday working on the concept of replacing entire server farms on-the-fly, during a service event. [139] [140]

In the 21st century, multi-core CPUs became commercially available. [141] Content-addressable memory (CAM) [142] has become inexpensive enough to be used in networking, and is frequently used for on-chip cache memory and modern microprocessors, although no computer system has yet implemented hardware CAMs for use in programming languages. Currently, CAMs (or associative arrays) in software are programming-language-specific. Semiconductor memory cell arrays are very regular structures, and manufacturers prove their processes on them; this allows price reductions on memory products. During the 1980s, CMOS logic gates developed into devices that could be made as fast as other types of circuit; computer power consumption could therefore be decreased dramatically. Unlike the continuous current draw of a gate based on other logic types, a CMOS gate only draws significant current during the ‘transition’ between logic states, except for leakage.

This has allowed computing to become a commodity which is now ubiquitous, embedded in many forms, from greeting cards and telephones to satellites. The thermal design power which is dissipated during operation has become as essential as computing speed of operation. And 2006 servers consumed 1.5% of the total energy budget of the U.S. [143] The energy consumption of computer data centers was expected to double to 3% of world consumption by 2011. The SoC (system on a chip) has compressed even more of the integrated circuitry into a single chip; SOCs are enabling phones and PCs to converge into a single hand-held wireless mobile devices. [144] Computing hardware and its software have even Monday become a metaphor for the operation of the universe.

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.[14] It has the longest rotation period (243 days) of any planet in the Solar System and rotates in the opposite direction to most other planets. It has no natural satellite. It is named after the Roman goddess of love and beauty. It is the second-brightest natural object in the night sky after the Moon, reaching an apparent magnitude of −4.6, bright enough to cast shadows.[15] Because Venus is an inferior planet from Earth, it never appears to venture far from the Sun; its elongation reaches a maximum of 47.8°.

Venus is a terrestrial planet and is sometimes called Earth’s “sister planet” because of their similar size, mass, proximity to the Sun, and bulk composition. It is radically different from Earth in other respects. It has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet’s surface is 92 times that of Earth. Venus is by far the hottest planet in the Solar System, with a mean surface temperature of 735 K (462 °C; 863 °F), even though Mercury is closer to the Sun. Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. It may have had water oceans in the past,[16][17] but these would have vaporized as the temperature rose due to a runaway greenhouse effect.[18] The water has probably photodissociated, and the free hydrogen has been swept into interplanetary space by the solar wind because of the lack of a planetary magnetic field.[19] Venus’s surface is a dry desertscape interspersed with slab-like rocks and is periodically resurfaced by volcanism.

As one of the brightest objects in the sky, Venus has been a major fixture in human culture for as long as records have existed. It has been made sacred to gods of many cultures, and has been a prime inspiration for writers and poets as the “morning star” and “evening star”. Venus was the first planet to have its motions plotted across the sky, as early as the second millennium BC,[20] and was a prime target for early interplanetary exploration as the closest planet to Earth. It was the first planet beyond Earth visited by a spacecraft (Mariner 2) in 1962, and the first to be successfully landed on (by Venera 7) in 1970. Venus’s thick clouds render observation of its surface impossible in visible light, and the first detailed maps did not emerge until the arrival of the Magellan orbiter in 1991. Plans have been proposed for rovers or more complex missions, but they are hindered by Venus’s hostile surface conditions.
The Venusian surface was a subject of speculation until some of its secrets were revealed by planetary science in the 20th century. Venera landers in 1975 and 1982 returned images of a surface covered in sediment and relatively angular rocks.[23] The surface was mapped in detail by Magellan in 1990–91. The ground shows evidence of extensive volcanism, and the sulfur in the atmosphere may indicate that there have been some recent eruptions.[24][25]

About 80% of the Venusian surface is covered by smooth, volcanic plains, consisting of 70% plains with wrinkle ridges and 10% smooth or lobate plains.[26] Two highland “continents” make up the rest of its surface area, one lying in the planet’s northern hemisphere and the other just south of the equator. The northern continent is called Ishtar Terra, after Ishtar the Babylonian goddess of love, and is about the size of Australia. Maxwell Montes, the highest mountain on Venus, lies on Ishtar Terra. Its peak is 11 km above the Venusian average surface elevation. The southern continent is called Aphrodite Terra, after the Greek goddess of love, and is the larger of the two highland regions at roughly the size of South America. A network of fractures and faults covers much of this area.[27]

The absence of evidence of lava flow accompanying any of the visible caldera remains an enigma. The planet has few impact craters, demonstrating that the surface is relatively young, approximately 300–600 million years old.[28][29] Venus has some unique surface features in addition to the impact craters, mountains, and valleys commonly found on rocky planets. Among these are flat-topped volcanic features called “farra”, which look somewhat like pancakes and range in size from 20 to 50 km across, and from 100 to 1,000 m high; radial, star-like fracture systems called “novae”; features with both radial and concentric fractures resembling spider webs, known as “arachnoids”; and “coronae”, circular rings of fractures sometimes surrounded by a depression. These features are volcanic in origin.[30]

Most Venusian surface features are named after historical and mythological women.[31] Exceptions are Maxwell Montes, named after James Clerk Maxwell, and highland regions Alpha Regio, Beta Regio, and Ovda Regio. The latter three features were named before the current system was adopted by the International Astronomical Union, the body which oversees planetary nomenclature.[32]

The longitudes of physical features on Venus are expressed relative to its prime meridian. The original prime meridian passed through the radar-bright spot at the centre of the oval feature Eve, located south of Alpha Regio.[33] After the Venera missions were completed, the prime meridian was redefined to pass through the central peak in the crater Ariadne