Second Part Here :-II Part

Q.1. Give short notes on various Input and Output Devices.

Ans.: The devices which are used to input the data and the programs in the computer are known as “Input Devices‟. These devices convert what we input, into a form that is understandable by a computer. It provides man to machine communication. Some of the I/O devices are explained below:

(1) Keyboard : The data and instructions are input by typing on the keyboard. The message typed on the keyboard reaches the memory unit of a computer. It‟s connected to a computer via a cable. Apart from alphabet and numeral keys, it has other function keys for performing different functions.

(2) Mouse : It‟s a pointing device. The mouse is rolled over the mouse pad, which in turn controls the movement of the cursor in the screen. We can click, double click or drag the mouse. Most of the mouse‟s have a ball beneath them, which rotates when the mouse in moved. The ball has 2 wheels of the sides, which in turn mousse with the movement of the ball. The sensor notifies the speed of its movements to the computer, which in turn moves the cursor/pointer on the screen.


(3) Scanner : Scanners are used to enter information directly in to the computers memory. This device works like a Xerox machine. The scanner converts any type of printed or written information including photographs into digital pulses, which can be manipulated by the computer.

(4) Track Ball : Track ball is similar to the upside- down design of the mouse. The user moves the ball directly, while the device itself remains stationary. The user spins the ball in various directions to effect the screen movements.


(5) Light Pen : This is an input device which is used to draw lines or figures on a computer screen. It‟s touched to the CRT screen where it can detect raster on the screen as it passes.

(6) Optical Character Rader : It‟s a device which detects alpha numeric characters printed or written on a paper. The text which is to be scanned is illuminated by a low frequency light source. The light is absorbed by the dark areas but reflected from the bright areas. The reflected light is received by the photocells.

(7) Bar Code Reader : This device reads bar codes and coverts them into electric pulses to be processed by a computer. A bar code is nothing but data coded in form of light and dark bars.

(8) Voice Input Systems : This devices converts spoken words to M/C language form. A micro phone is used to convert human speech into electric signals. The signal pattern is then transmitted to a computer when it‟s compared to a dictionary of patterns that have been previously placed in a storage unit of computer. When a close match is found, the word is recognized.

(9) Plotter : Plotter is an O/P device that is used to produce graphical O/P on papers. It uses single color or multi color pens to draw pictures as blue print etc.

(10) Digital Camera : It converts graphics directly into digital form. It looks like an ordinary camera, but no film is used therein, instead a CCD (changed coupled Divide) Electronic chip in used. When light falls, on the chip though the lens, it converts light waves into electrical waves.

Q.2. What is a Printer and what are the different types of Printers?

Ans.: Printers are O/P devices used to prepare permanent O/P on paper. Printers can be divided into two main categories :


(1) Impact Printers : In this hammers or pins strike against a ribbon and paper to print the text. This mechanism is known as electro-mechanical mechanism. They are of two types.

(i) Character Printer
(ii) Line Printer

(i) Character Printer : It prints only one character at a time. It has relatively slower speed. Eg. Of them are Dot matrix printers.
Dot Matrix Printer : It prints characters as combination of dots. Dot matrix printers are the most popular among serial printers. These have a matrix of pins on the print head of the printer which form the character. The computer memory sends one character at a time to be printed by the printer. There is a carbon between the pins & the paper. The words get printed on the paper when the pin strikes the carbon. There are generally 24 pins.

(ii) Line Printer : It prints one line of text at a time. They have higher speed compared to character printers. These printers have a poor quality of O/P. Chain printers and Drum printers are examples of line printers.

(2) Non-Impact Printers : There printers use non-Impact technology such as ink-jet or laser technology. There printers provide better quality of O/P at higher speed. 

These printers are of two types :

(i) Ink-Jet Printer : It prints characters by spraying patterns of ink on the paper from a nozzle or jet. It prints from nozzles having very fine holes,from which a specially made ink is pumped out to create various letters and shapes. The ink comes out of the nozzle in a form of vapors. After passing through a reflecting plate, it forms the desired letter/shape at the desired place.


(ii) Laser Printer : It prints the entire page in one go. These printers have photo sensitive drum made of silicon. This drum is coated with recharge photoconductive, which is extremely sensitive to light. This drum is exposed to the laser rays reflected from the shapes to be printed. The area where there rays fall gets discharged. This drum while rotating comes in contact with toner and the toner gets attached to the discharged area on the drum. Then when the drum comes in contact with paper, the toner that has got attached to the drum in the original shape gets attached to the paper & hence printing takes place. The paper is slightly heated and the toner gets permanently attached to it.

Q.3. What is the Refresh Rate?

Ans.: The refresh rate is the number of times in a second that display the data it‟s being given. This is distinct from the measure of from rate in that the refresh rate includes the repeated drawing of identical while trans rate measures how a video source can lead an entire frame of new data to a display.

Q.4. What are the different kinds of Resolutions in the Monitor?

Ans.: Resolution refers to the sharpness, or detail of the usual image. It‟s a primary function of the monitor & it‟s determined by the beam size & dot pitch. The screen is made up of a number of pixels. A completes screen image consists of thousand of pixels & the screen resolution in the maximum no. of displayable pixels. Higher the resolution, the more pixels can be displayed. Resolutions are of different for different video standards as listed below :

(a) VGA : 1640 x 480
(b) SVGA : 800 x 600
(c) XGA : 1024 x 768
(d) SXGA : 1400 x 1050




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