Hi guys I will give you some basic knowledge about computer .In this article I will learn you some input device of a computer like keyboard,mouse, ocr, microphone,scanner, because it is very important for you it is always ask in general competion and also give you a general knowledge. I will try to understand you every topic and also I describe this topic in detail which is helpful for you to understand easily.

So let's starts.

First of all know that...

What is input device.



The input unit is responsible for accepting input i.e., data and instructions from the user This work is accomplished with the help of input devices. Device, in general, refers to an equipment or a complete hardware unit. Let us learn more about some most common input devices. lets talk about some common input device which are commonly used in every day.

 1. The Keyboard  : Keyboard is a typewriter like device which is used to type in the letters, digits and commands. A keyboard contains a matrix of switches (one switch per key). Each key, when pressed, sends a digital code to the computer that determines which key has been pressed.



 2.The Mouse : The mouse is a pointing device that points to a position on computer screen. Mouse controls movement of pointer (also called mouse pointer) on screen. When a mouse moves on a flat surface, the cursor on the screen also moves in the direction of mouse's movement. A mouse generally has two or three buttons and it may or may not have a wheel.


(Do you know that mouse was invented by Douglas Agelbart of Stanford Research Centre in 1963 .)

3.Microphone. ( The common name is mic)


 We can send sound input to computer through a special input device called microphone or mic in short. A mic converts the sound received into computer's format, which is called digitized sound or digital audio. A mic can work if your computer has a special hardware known as sound card. 

4.Scanner

 A scanner is a device similar to a photocopier. A scanner creates an electronic form of the printed image, which can later be manipulated, changed and modified according to the requirements. Scanners come in a variety of sizes from hand-held models to desktop models as discussed below .

 (i) Hand-held Scanners are very small which can be held in a hand.

 (ii) Flatbed Scanners are larger and more expensive scanners but they definitely create higher quality images. These scanners have a flat surface on which the printed image to be scanned, is placed. 

(iii) Drum Scanners are medium-size scanners with a rolling drum. The sheet is fed through the scanners so that the drum rolls over the entire sheet to be scanned.

 5.Touch Screens 

A touch screen can detect where on the screen surface you are touching. Touch screens are often used in mobile devices such as phones and tablets where you would not have space for a traditional keyboard.

6.Barcode Reader 

A barcode reader is used to read barcodes which can be found on products in shops. The barcode uses lasers to identify the position and thickness of the bars. Magnetic Stripe Reader A magnetic stripe can be found on the backs of many credit cards, security cards of hotel rooms to gain access to rooms etc. Data is encoded magnetically on the strip and read by a machine as it is swiped. 

Some other input devices are.

 1. OMR (Optical Mark Reader) that can read marks at designated positions such as the OMR sheets you use to answer questions on a multiple choice exam paper or survey.

 2.OCR (Optical Character Reader) that can scan a printed document and convert it into editable text. 

3.MI (Magnetic Ink Character Reader) that can read the magnetized ink characters as you can see on bank cheques. Light Pen, a light-sensitive input device shaped like a pen, used to draw on the computer screen or to make menu selections.

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Today i will give you very interesting topic which always ask in competitive examination. This question is very important for those students who will ready for general competitive examination. This question is always ask in India for bank,ssc, po ,or other examination.

so lets starts.....

first of all what what is the question.

then guys the the question is.....

what is vacuole?



 Vacuoles are fluid-filled or solid-filled and membrane-bounded spaces. They are a kind of storage sacs. In animal cells, the vacuoles if present are small and temporary. They store water, glycogen and proteins. The vacuolar membrane is typically a single unit membrane and is often associated with the maintenance of water balance (e.g., they serve as osmoregulatory organelles in protozoans) or ingestion of nutrient material (food vacuole). Thus, food vacuole of a single celled organisms such as Amoeba or Paranieciuni, contains the food item that the animal has consumed.

above answer is vacuoles in animal 

But in plant below is your answer...

In plant cells, the vacuoles are large, distinct and permanent. In mature plant cells the vacuole occupies almost the entire (i.e., 90%) volume of the cell. Because of the central position of a vacuole, the nucleus and other cell organelles in plant cells are pushed near the boundary wall. The vacuole is bounded by a membrane, called tonoplast. The vacuole is filled with cell sap which is a watery solution rich in sugars, amino acids, proteins, minerals and metabolic wastes (such as anthocyanins, alkaloids).

This question is the part of biology where you learn about vacuole.


properties of vacuoles.

Vacuoles help to maintain the osmotic pressure in a cell (osmoregulation). by-products or end products of plant cells. They provide turgidity and rigidity.

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 1.Short Distance wireless media.

 The short distance wireless media can support transmission within a rang covering a few meters up to a few miles/kilometers.


(a) Infrared

use of this type of transmi garage doors, wireles transmission media.
e of transmission uses infrared light to send data. You can see the this type of transmission in everyday life - TV remotes, automotive doors, wireless speakers etc., all make use of infrared as
infrared light transmits data through the air and can propagate
ughout a room (bouncing off surfaces), but will not penetrate walls. he infrared transmission has become common in PDAs (Personal digital esistants) e.g., hand held devices like palm pilots etc. The infrared transmission is considered to be a secure one.

(b) Laser

The laser transmission requires direct line-of-sight. It is unidirectional like microwave, but has much higher speed than microwaves. The laser transmission requires the use of a laser transmitter and a photo-sensitive Forever at each end. The laser transmission is point-to-point transmission, typically between buildings. But lasers have a certain disadvantage, which is : laser transmission can be adversely affected by weather. (c) Bluetooth Bluetooth is a telecommunications industry specification that describes how mobile phones, computers and personal digital assistants (PDAs) can be easily interconnected using a short-range wireless connection. Using this technology, users of cellular phones, pagers and personal digital assistants can buy a three-in-one phone that can double as a portable phone at home or in the office, get quickly synchronized with information in a desktop or notebook computer, initiate the sending or receiving of a fax, initiate a print-out, and, in general, have all mobile and fixed computer devices be totally coordinated. Bluetooth requires that a low-cost transceiver chip be included in each device. The transceiver transmits and receives in a previously unused frequency band of 2.45 GHz that is available globally (with some variation of bandwidth in different countries).

(d) Wi-Fi 




Wi-Fi refers to Wireless Fidelity, which lets you connect to the Internet without a direct line from your PC to the ISP. For Wi-Fi to work, you need:



2. Long distance Wireless media .

The long distance wireless media can support communication over a longer distance upto thousands of kilometres. Long distance wireless communication media include :

(a) Microwave

 Microwave signals are used to transmit data without the use of cables, similar to that of radio and television signals, but at different frequency range. It is line-of-sight transmission, which means the signal travels in a straight line free of material obstacles.

 (b) Radio Wave 

The transmission making use of radio frequencies is termed as radio-wave transmission. Radio Frequencies are in the range of 300 kHz to 10 GHz.

 (c) Satellite

Radio wave can be classified by frequency and wavelength. When the frequency is higher than 3 GHz, it is named microwave. Satellite communication is special case of microwave relay system. Satellite communication use the synchronous satellite to relay the radio signal transmitted from ground station. In satellite communication the earth station consists of a satellite dish that functions as an antenna and communication equipment to transmit and receive data from satellites passing overhead. A number of communication satellites, owned by both governments and private organisations, have been placed in stationary orbits about 22,300 miles above the earth's surface. These satellites act as relay stations for communication signals. The satellites accept data/ signals transmitted from an earth station, amplify them, and retransmit them to another eart station. Using such a setup, data can be transmitted to the other side the earth in only one step.