Isnin, 6 Ogos 2012

computer components


hardware of modem

1. Monitor
2. Motherboard
3. CPU
4. RAM
5. Expansion cards
6. Power supply
7. Optical disc drive
8. Hard disk drive
9. Keyboard
10. Mouse

COMPUTER OF CLASSIFICATION


Computer of Classification

Until recently computers were classifieds as microcomputers, super minicomputers, mainframes, and supercomputers. Technology, however, has changed and this classification is no more relevant. Today all computers used microprocessors as their CPU. Thus classification is possible only through their mode of use. Based on mode of use we can classify computers as Palms, Laptop PCs, Desktop PCs and Workstations. Based on interconnected computers we can classify computers we can classify them as distributed computers and parallel computers.

Palm PCs or Simputer
With miniaturization and high-density packing of transistor on a chip, computers with capabilities nearly that of PCs which can be held in a palm have emerged. Palm accept handwritten inputs using an electronic pen which can be used to write on a Palm’s screen (besides a tiny keyboard), have small disk storage and can be connected to a wireless network. One has to train the system on the user’s handwriting before it can be used as a mobile phone, Fax, and e-mail machine. A version of Microsoft operating system called Windows-CE is available for Palm.An Indian initiative to meet the needs of rural population of developing countries is called Simputer. Simputer is a mobile handheld computer with input through icons on a touch sensitive overly on the LCD display panel. A unique feature of Simputer is the use of free open source OS called GNU/Linux. The cost of ownership is thus low as there is no software cost for OS. Another unique feature of Simputer not found in Palm, is a smart card reader/writer, which increases the functionality of the Simputer including possibility of personalization of a single Simputer for several users.

COMPUTER HISTORY AND GENERATION

Computer history and generations
The First Generation:  1946-1958 (The Vacuum Tube Years)
        The first generation computers were huge, slow, expensive, and often undependable.  In 1946two Americans, Presper Eckert, and John Mauchly built the ENIAC electronic computer which used vacuum tubes instead of the mechanical switches of the Mark I.  The ENIAC used thousands of vacuum tubes, which took up a lot of space and gave off a great deal of heat just like light bulbs do.  The ENIAC led to other vacuum tube type computers like the EDVAC (Electronic Discrete Variable Automatic Computer) and the UNIVAC I (UNIVersal Automatic Computer).

        The vacuum tube was an extremely important step in the advancement of computers.  Vacuum tubes were invented the same time the light bulb was invented by Thomas Edison and worked very similar to light bulbs.  It's purpose was to act like an amplifier and a switch.  Without any moving parts, vacuum tubes could take very weak signals and make the signal stronger (amplify it).  Vacuum tubes could also stop and start the flow of electricity instantly (switch).  These two properties made the ENIAC computer possible.
        The ENIAC gave off so much heat that they had to be cooled by gigantic air conditioners.  However even with these huge coolers, vacuum tubes still overheated regularly.  It was time for something new.
The Second Generation:  1959-1964 (The Era of the Transistor)
        The transistor computer did not last as long as the vacuum tube computer lasted, but it was no less important in the advancement of computer technology.  In 1947 three scientists, John Bardeen, William Shockley, and Walter Brattain working at AT&T's Bell Labs invented what would replace the vacuum tube forever.  This invention was the transistor which functions like a vacuum tube in that it can be used to relay and switch electronic signals.
        There were obvious differences between the transisitor and the vacuum tube.  The transistor was faster, more reliable, smaller, and much cheaper to build than a vacuum tube.  One transistor replaced the equivalent of 40 vacuum tubes.  These transistors were made of solid material, some of which is silicon, an abundant element (second only to oxygen) found in beach sand and glass.  Therefore they were very cheap to produce.  Transistors were found to conduct electricity faster and better than vacuum tubes.  They were also much smaller and gave off virtually no heat compared to vacuum tubes.  Their use marked a new beginning for the computer.  Without this invention, space travel in the 1960's would not have been possible.  However, a new invention would even further advance our ability to use computers.
 The Third Generation:  1965-1970 (Integrated Circuits - Miniaturizing the Computer)
Transistors were a tremendous breakthrough in advancing the computer.  However no one could predict that thousands even now millions of transistors (circuits) could be compacted in such a small space.  The integrated circuit, or as it is sometimes referred to as semiconductor chip, packs a huge number of transistors onto a single wafer of silicon. Robert Noyce of Fairchild Corporation and Jack Kilby of Texas Instruments independently discovered the amazing attributes of integrated circuits.  Placing such large numbers of transistors on a single chip vastly increased the power of a single computer and lowered its cost considerably.
        Since the invention of integrated circuits, the number of transistors that can be placed on a single chip has doubled every two years, shrinking both the size and cost of computers even further and further enhancing its power.  Most electronic devices today use some form of integrated circuits placed on printed circuit boards-- thin pieces of bakelite or fiberglass that have electrical connections etched onto them -- sometimes called a mother board.

        These third generation computers could carry out instructions in billionths of a second.  The size of these machines dropped to the size of small file cabinets. Yet, the single biggest advancement in the computer era was yet to be