Hardware

**Hardware** //(definition)//: The physical parts of the computer which we can touch, including the inside parts and devices that you can connect to the computer.

Below, I will be explaining about:
 * Computers
 * Input Devices
 * Output Devices
 * Storage Devices //(stored, inactive)//
 * Processor and Memory //(in use, active)//




Computers
Computers are grouped according to their size, power design and cost. Here are the list of each group.


 * Supercomputers:[[image:http://snitchjunkie.files.wordpress.com/2008/08/supercomputer-banks-noaa21.jpg?w=300&h=195 width="300" height="195" align="right" caption="Supercomputers" link="http://snitchjunkie.files.wordpress.com/2008/08/supercomputer-banks-noaa21.jpg"]]** These are the fastest and the most expensive type of computers. Since it has thousands of processing chips put together, it has a very strong processing power. This is useful for science and engineering like weather forecast and performing complex graphical techniques. One of the strong ones can even carry out a thousand trillion calculations per second.


 * Mainframe computers:** Are also powerful, and allows hundreds of computers working simultaneously. These are mostly used in large companies in order to do their data processing, scientists for mathematical calculations, and for Internet as network servers.


 * Microcomputers:** The most basic type of computers that people use at homes, schools and in most businesses. These computers can also be divided into two major types by their design: desktop and laptops. Desktop computers has a monitor, tower, keyboard and mouse combined together. On the other hand, laptop computers are light and portable, unlike desktops. It can work by its own but you can also connect peripheral devices if you need some.


 * PDA:** Personal digital assistants (PDA) are [[image:http://sartechnology.ca/sartechnology/PDA6.jpg width="166" height="172" align="left" caption="PDA"]]known as palmtop devices. It is small that you can hold it in one hand, and you input data using a stylus since its screen are touch sensitive. This is useful for keeping contact information, diaries, note taking, playing games and using e-mails.


 * Embedded computers:** Many modern electronic devices has computers embedded in them, like telephones, cameras, and remote comtroller. Even though it does not have monitors and keyboards, it can input and output data needed; input from its sensors and outputs by carrying out its operation.

Input Devices

 * Keyboard:** There are three types of keyboards: QWERTY, braille, and concept. For QWERTY keyboards, users press keys that inputs data that will be meaning as a symbol or a letter. The name comes from the first six letters on the top row in keyboards.Some of it considers ergonomics by making the layout curved so that your hands will be less stressful. Compared to other devices, the inputting of data by keyboards are quite slow. Braille keyboards are for the visually impaired and uses the Braille code. Concept keyboards are flat panels of switches contact by a flexible membrane. It normally has pictures or symbols over it and each switch you press will respond differently. It is used in primary schools and in restaurants.


 * Mouse:** Mouse is used for controlling the pointer on the screen. Old mouse have a ball underneath, that moves as it is moved by a user. Today most mouse are optical, which uses light beam and detector instead. The light is shined on a surface, and movement is detected by the changes in the way light is reflected back off the surface. Most mouse have two buttons that can click, double-click and drag icons. It also have a wheel that allows the user to scroll up and down, and zoom in and out a page. There are mouse with cables, but also mouse that have infra-red or wireless connection.


 * Touch pad:** found on laptop computers and function like a mouse. Moving your finger across the pad will control the movement of the pointer on the computer. Tapping the pad clicks on a icon, but there are also two switches that work as left and right mouse buttons.


 * Touch screen:** Touch-sensetive screens work since there are beams of infra-red light in front of the monitor glass. When touched, two rays, a ray travelling side to side and a ray travelling top to buttom is blocked. The computer detects the finger's position by this. It is used as information system in museum, airports and tourist offices.


 * Scanner:** Used to input images and text into the computer by the machine recongnizing them by putting a page on a glass plate, and lighting it. By the reflection of light, the computer will know which parts have what color.


 * OMR:** Optical mark readers detect marks made on paper using infra-red light. If there is no mark on the paper, much of the light will be reflected than when there is a mark. OMRs are used for inputting numbers for lottery tickets and answers for multiple-choice test questions.


 * OCR:** Optical character recognition is a software that is used for scanning text.
 * Remote controllers:** For television, it controls to change the channel and volume. When a button is pressed, light beem will travel to the reciever on the television, from the light-emitting diode on the remote controller.


 * Bar code reader:** Barcode is a pattern for black and white stripes. Readers sends laser to the barcode, and then recieve signals as the reflection of light or not reflecting any light.


 * MICR:** Magnetic ink character recognition is used for bank cheques, and it reads information written in magnetic ink.


 * Smart card:** It is a card that has ICC (Integrated chip card) in it. The information that can be held on the card are the amount of money, account information and cost of goods.


 * Microphone:** used for speech and voice input.


 * MIDI:** Musical Instrument Digital Interface is used for creating and editting music. Data is inputted through a keyboard, or sensors that respond when being struck.

Output Devices

 * Monitors:** Monitors, or vidual display unit are the most common type of an output device. There are several types of displays: LCD, gas-plasma display, and carthode ray tube.


 * Projectors:** Projects what is displayed on a computer monitor, directly to a screen.
 * Printers:** Laser, ink-jet and dot-matrix.
 * Plotter:** used for engineers, architects, and scientists printing their plans on a large sheet of paper.
 * Speakers:** Outputs sound and voice.

Storage Devices

 * Bit:** the smallest chunk of information that a computer can work with.


 * Bytes:** One byte is equal to eight bits. It is the unit when measuring the memory in the computer. It uses binary code with eight 1 or 0s. One letter typed in from a keyboard is also one byte.


 * Hard disks:** Measured in gigabytes. It holds the operating system, application system, games and data from programs.


 * Compact Discs:** Are currently getting replaced by DVDs, but it can hold on data like text, sound, image and video. There are three types of this: CD-ROM that you can only read information already stored, CD-R that you can write information but only once, and CD-RW which allows you to record and delete as many time as you want but you have to delete the whole thing when you do.

Processor and Memory

 * CPU:** stands for Central Processing Unit and it is the brain of the computer that processes all information and instruction by the computer. It gives instructions to the software, does arithmetic opeartion and it can also store temporaly data.


 * RAM:** Random acess memory is where the processor recieves instruction and data needed for it to work. It is only a temporaly storage, so when you turn off the computer, the data will be lost.


 * ROM:** Read only memory contains instructions and is a memory that can only be read. It checks hardware and operate hard disk. ROM makes sures that the operating system that is stored can be loaded on the computer.

(Volatile Memory: Any memory that its information will be lost when the computer is turned off.)