Monday 9 January 2012

Computer Classification

There are many computers which are different from each other in various aspects. Classification of computers are given below.

(1) Micro computers: These computers use a microprocessor chip and this chip is used instead of CPU means that this microprocessor chip works as a CPU.
These computers are also called personal computers. Two major types of these computers are laptop or Desktop computers. Only one user uses these computers at time that's why they are also known as personal computers.

(2) Mini Computers: These are powerful computer. These computers come into existence in 1960s at that time mainframe computer was very costly. Mini computers were available in cheap prices, so users start using it.

(3) Mainframe Computer: It as a very powerful and large computer. You can get idea of its power as it can handle processing of many users at a time.
Terminals are used to connect a user to this computer and users submit there task through mainframe. Terminal is a device which has keyboard and a screen. By using terminal users put inputs into the computer and get the output through screen.

(4) Super Computers: As the name "super computer" specifies that these are most powerful computers even than mainframe. Actually, when we optimize a mainframe computer then we get super computer.

(5) Microprocessor: You will find these computers everywhere. Microprocessor chips are used in many devices as I-pod, DVD, headphone etc.
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Computer Components

MOTHER BOARD

Main article: Motherboard
The motherboard is the main component inside the case. It is a large rectangular board with integrated circuitry that connects the other parts of the computer including the CPU, theRAM, the disk drives (CD, DVD, hard disk, or any others) as well as any peripherals connected via the ports or the expansion slots.
Components directly attached to the motherboard include:
  • The CPU (Central Processing Unit) performs most of the calculations which enable a computer to function, and is sometimes referred to as the "brain" of the computer. It is usually cooled by a heat sink and fan. Newer CPUs include an on-die Graphics Processing Unit (GPU).
  • The Chipset mediates communication between the CPU and the other components of the system, including main memory.
  • The RAM (Random-access Memory) stores resident part of the current running OS (OS core and so on) and all running processes (application parts, using CPU or input/output (I/O) channels or waiting for CPU or I/O channels).
  • The BIOS (Basic Input Output System) includes boot firmware and power management. The tasks are handled by operating system drivers. Newer motherboards use Unified Extensible Firmware Interface (UEFI) instead of BIOS.
  • The ROM (Read-only Memory) stores the initial program that runs when the computer is powered on or otherwise begins execution (Bootstrapping also known as "booting" or "booting up"). Usually stores the BIOS or UEFI.
  • Internal buses connect the CPU to various internal components and to expansion cards for graphics and sound.
    • Current
      • The north bridge memory controller, for RAM and PCI Express
        • PCI Express, for expansion cards such as graphics, lannd and physics processors, and high-end network interfaces
      • PCI, for other expansion cards
      • SATA, for disk drives
      • ATA
    • Obsolete
      • AGP (superseded by PCI Express)
      • VLB VESA Local Bus (superseded by AGP)
      • ISA (expansion card slot format obsolete in PCs, but still used in industrial computers)
  • External bus controllers support ports for external peripherals. These ports may be controlled directly by the south bridge I/O controller or based on expansion cards attached to the motherboard through the PCI bus.

[EDIT]POWER SUPPLY

Main article: Power supply unit (computer)
Inside a custom-built computer: the power supply at the bottom has its own cooling fan.
A power supply unit (PSU) converts alternating current (AC) electric power to low-voltage DC power for the internal components of the computer. Some power supplies have a switch to change between 230 V and 115 V. Other models have automatic sensors that switch input voltage automatically, or are able to accept any voltage between those limits. Power supply units used in computers are nearly always switch mode power supplies (SMPS). The SMPS provides regulated direct current power at the several voltages required by the motherboard and accessories such as disk drives and cooling fans.

[EDIT]REMOVABLE MEDIA DEVICES

Main article: Computer storage
  • CD (compact disc) - the most common type of removable media, suitable for music and data.
    • CD-ROM Drive - a device used for reading data from a CD.
    • CD Writer - a device used for both reading and writing data to and from a CD.
  • DVD (digital versatile disc) - a popular type of removable media that is the same dimensions as a CD but stores up to 12 times as much information. It is the most common way of transferring digital video, and is popular for data storage.
    • DVD-ROM Drive - a device used for reading data from a DVD.
    • DVD Writer - a device used for both reading and writing data to and from a DVD.
    • DVD-RAM Drive - a device used for rapid writing and reading of data from a special type of DVD.
  • Blu-ray Disc - a high-density optical disc format for data and high-definition video. Can store 70 times as much information as a CD.
    • BD-ROM Drive - a device used for reading data from a Blu-ray disc.
    • BD Writer - a device used for both reading and writing data to and from a Blu-ray disc.
  • HD DVD - a discontinued competitor to the Blu-ray format.
  • Floppy disk - an outdated storage device consisting of a thin disk of a flexible magnetic storage medium. Floppies are used today mainly for loading device drivers not included with an operating system release (for example, RAID drivers).
  • Zip drive - an outdated medium-capacity removable disk storage system, first introduced by Iomega in 1994.
  • USB flash drive - a flash memory data storage device integrated with a USB interface, typically small, lightweight, removable, and rewritable. Capacities vary, from hundreds of megabytes (in the same range as CDs) to tens of gigabytes (surpassing, at great expense, Blu-ray discs).
  • Memory Card - a flash memory data storage device used to store digital information found on many mobile devices. They are smaller and lighter then USB flash drives. They are thin, removable and able to retain data without power. Common types of formats are SD and MS.
  • Tape drive - a device that reads and writes data on a magnetic tape, used for long term storage and backups.

[EDIT]SECONDARY STORAGE

Hardware that keeps data inside the computer for later use and remains persistent even when the computer has no power.
  • Hard disk - for medium-term storage of data.
  • Solid-state drive - a device similar to hard disk, but containing no moving parts and stores data in a digital format.
  • RAID array controller - a device to manage several internal or external hard disks and optionally some peripherals in order to achieve performance or reliability improvement in what is called a RAID array.

[EDIT]SOUND CARD

Main article: Sound card
Enables the computer to output sound to audio devices, as well as accept input from a microphone. Most modern computers have sound cards built-in to the motherboard, though it is common for a user to install a separate sound card as an upgrade. Most sound cards, either built-in or added, have surround sound capabilities.

[EDIT]INPUT AND OUTPUT PERIPHERALS

Main article: Peripheral
Input and output devices are typically housed externally to the main computer chassis. The following are either standard or very common to many computer systems.
Wheel mouse

[edit]Input

Main article: Input device
  • Text input devices
    • Keyboard - a device to input text and characters by depressing buttons (referred to as keys or buttons).
  • Pointing devices
    • Mouse - a pointing device that detects two dimensional motion relative to its supporting surface.
      • Optical Mouse - uses light (laser technology) to determine mouse motion.
    • Trackball - a pointing device consisting of an exposed protruding ball housed in a socket that detects rotation about two axes.
    • Touchscreen - senses the user pressing directly on the monitor.
  • Gaming devices
    • Joystick - a hand-operated pivoted stick whose position is transmitted to the computer.
    • Game pad - a hand held game controller that relies on the digits (especially thumbs) to provide input.
    • Game controller - a specific type of controller specialized for certain gaming purposes.
  • Image, Video input devices
    • Image scanner - a device that provides input by analyzing images, printed text, handwriting, or an object.
    • Web cam - a video camera used to provide visual input that can be easily transferred over the internet.
  • Audio input devices
    • Microphone - an acoustic sensor that provides input by converting sound into electrical signals.

[edit]Output

Main article: Output device
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Computer History and Generations

EACH GENERATION OF COMPUTER IS CHARACTERIZED BY A MAJOR TECHNOLOGICAL DEVELOPMENT THAT FUNDAMENTALLY CHANGED THE WAY COMPUTERS OPERATE, RESULTING IN INCREASINGLY SMALLER, CHEAPER, MORE POWERFUL AND MORE EFFICIENT AND RELIABLE DEVICES.

The history of computer development is often referred to in reference to the different generations of computing devices. Each generation of computer is characterized by a major technological development that fundamentally changed the way computers operate, resulting in increasingly smaller, cheaper, more powerful and more efficient and reliable devices. Read about each generation and the developments that led to the current devices that we use today.

First Generation (1940-1956) Vacuum Tubes

The first computers used vacuum tubes for circuitry and magnetic drums for memory, and were often enormous, taking up entire rooms. They were very expensive to operate and in addition to using a great deal of electricity, generated a lot of heat, which was often the cause of malfunctions.
First generation computers relied on machine language, the lowest-level programming language understood by computers, to perform operations, and they could only solve one problem at a time. Input was based on punched cards and paper tape, and output was displayed on printouts.
The UNIVAC and ENIAC computers are examples of first-generation computing devices. The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951.

Second Generation (1956-1963) Transistors

Transistors replaced vacuum tubes and ushered in the second generation of computers. The transistor was invented in 1947 but did not see widespread use in computers until the late 1950s. The transistor was far superior to the vacuum tube, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than their first-generation predecessors. Though the transistor still generated a great deal of heat that subjected the computer to damage, it was a vast improvement over the vacuum tube. Second-generation computers still relied on punched cards for input and printouts for output.
Second-generation computers moved from cryptic binary machine language to symbolic, or assembly, languages, which allowed programmers to specify instructions in words. High-level programming languages were also being developed at this time, such as early versions of COBOL and FORTRAN. These were also the first computers that stored their instructions in their memory, which moved from a magnetic drum to magnetic core technology.
The first computers of this generation were developed for the atomic energy industry.

Third Generation (1964-1971) Integrated Circuits

The development of the integrated circuit was the hallmark of the third generation of computers. Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers.
Instead of punched cards and printouts, users interacted with third generation computers through keyboards and monitorsand interfaced with an operating system, which allowed the device to run many different applications at one time with a central program that monitored the memory. Computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors.

Fourth Generation (1971-Present) Microprocessors

The microprocessor brought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip. What in the first generation filled an entire room could now fit in the palm of the hand. The Intel 4004 chip, developed in 1971, located all the components of the computer—from the central processing unit and memory to input/output controls—on a single chip.
In 1981 IBM introduced its first computer for the home user, and in 1984 Apple introduced the Macintosh. Microprocessors also moved out of the realm of desktop computers and into many areas of life as more and more everyday products began to use microprocessors.
As these small computers became more powerful, they could be linked together to form networks, which eventually led to the development of the Internet. Fourth generation computers also saw the development of GUIs, the mouse and handhelddevices.

Fifth Generation (Present and Beyond) Artificial Intelligence

Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. The use of parallel processing and superconductors is helping to make artificial intelligence a reality. Quantum computation and molecular and nanotechnology will radically change the face of computers in years to come. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self-organization.
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