keyboard divya

8/6/2019 Keyboard Divya

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INTRODUCTION

KEYBOARD IS AN INPUT DEVICE.

The keyboard, like a typewriter, is used for enteringcharacters (such as letters, numbers and symbols).

-> Keyboard layouts are different.The Qwerty keyboard was designed in 1868 inMilwaukee by Christopher Latham Sholes, whoplaced the keys corresponding to the most commonlyused letter pairs at opposite ends of the keyboard, in

order to prevent the typewriter hammers of the timefrom becoming jammed with one another. This keyboard was f irst sold by the company Remington in1873.



Dvorak

In 1936, August Dvorak (a professor at theUniversity of Washington) created a keyboardwhose keys were arranged solely witheff iciency in mind. The Dvorak keyboardplaced all the vowels of the alphabet and thef ive most common consonants on the central row so they could be easily accessed, whilealso evenly dividing the work between the leftand right hands.



Keyboard connector

Keyboards are generally plugged into the rear of the CPU, on the motherboard

, using a purple PS/2

connector:



How it works

When a key is pressed, an electrical contact is formed between the row and column.The electric signals are transmitted to a microcontroller, which sends a code (BCD,

ASCII or Unicode) to the computer describing the character which corresponds tothat key.

Inside the keyboard, there are metallic plate, circuit board (key matrix) andprocessor, which are responsible for transferring information from the keyboard to

the computer.



Types of keyboards

There are four types of keyboards for PCs. The first

three were invented by IBM, while the latter is the result of

changes made when Microsoft Windows 95 was released. These

are the four kinds of keyboards:

The 83-key keyboard (PC/XT)

The 84-key keyboard (PC/AT)

The 102-key keyboard, called the extended keyboard

The 105-key Microsoft Windows 95-compatible keyboard.



1) PC/XT keyboards(83 keys)

This was criticised for the arrangement of

thek

eys(

espec

ia

lly the Shift and Enter

key

s)

which were too small and poorly placed).No LED indicator.

2) PC/AT keyboards(84 keys)

This keyboard corrected the errors , by resizing the Shift and Enter keys.

Additionally, the keyboard was bidirectional, meaning that it could

display its status using LED indicatorlights

3) Extended keyboards(102 keys)

This new keyboard included different blocks of keys: The f unction keys were moved to

the top of the keyboard, while cursor control keys, represented by arrows, were added

Microsoft Windows-compatible keyboards

These three new keys are, from left to right:The l eft Windows key,The right Windows key

The Appl ication key.



ESCAPE KEY

The Escape key is used to cancel the data entry and toterminate the execution of the commands and programs.

The Function keys are numbered F1, F2, F3,....F12. These are programmable keys used toissue commands. For example, F1 is most often used to access the Help f ile for a program.

FUNCTION KEYS

PRINT SCREEN KEY

It used for the screen shots.



The Scroll Lock key is more useful underDOS where pressing it will stop text on the screenfrom scrolling off the top of the screen. This gives you time to read or print it beforecontinuing.

Pause key is little used under Windows. Under DOS it is used to halt actions in

progress, often so that messages on the screen can be read before they scroll off

the screen.

SCROLL LOCK

PAUSE

TAB KEY

Tab key is used in documents to move the cursor over to the right to a pre-setpoint.



When the Caps Lock key is on, pressing any alphabetic key will result in an upper case(capital) letter. The number and symbol keys are not affected.

SHIFT KEY

The Shift key is used in combination with the alphabetic keys to get upper case.With a numeric/symbol key, using the Shift key will produce the character at the

top of the key.

The Control key does nothing all by itself. It must be pressed in combination withother keys. When used in combination, the Control key changes the normal effect of akey. Exactly what will happen depends on the software in use at the time.

CAPS LOCK

CONTROL KEY



ALT KEY

The Alt key doesn't do anything by itself. But if you hold it down while pressinganother key, an alternative meaning for each key will be established.

SPACE BAR

The Spacebar is used to enter blank spaces in text.

ARR OW KEYS

Thes

e fou

rk

eys

areus

ed tom

ove the cu

rsor on the

screen.



ALPHABETK EYS

The letters of the alphabet and some punctuation marks are in these three rows.The order of the keys is called QWERTY from the order of the keys on the top row.

This arrangement of the letters was inherited from the typewriter.

On this row of keys you will see two characters, one at the top of the key and one atthe bottom. The upper character is a symbol and is accessed by holding the Shift

key down while pressing the key. Numbers can also be typed from the NumericKeypad.

NUMBER/SYMBOLK EYS



1)Eclipse LiteTouch LCDTouch screen Keyboard



2)Optimus Tactus Touch Keyboard



3) Pc Inside a Keyboard

This new generation All-in-One PC in a keyboard not only takes up farless desktop space, but also puts an Intel® Core 2 Quad CPU with all its features and performance at your f ingertips. Simply place it on yourdesktop, plug in a monitor and you are done.



4) Silicone Keyboard with Mouse (SKM)

This silicone keyboard with integrated mouse is the f irst choicefor environments that require washable keyboards. The rigidsurface of the keyboard offers to the user the best tactilefeedback feeling, which is similar to a regular keyboard of personal computer. SKM Keyboard is a 100% compatible to astandard keyboard and does not require any special driver. SKMkeyboard as 102 keys and a "QWERTY" (or "AZERTY") typeconf iguration. A single type A USB connector supports thekeyboard and the mouse devices.

FactsIdeal for hospitals, laboratories, at nursing stations, on medical carts or anywhere cleanliness and reliability are of outmostconcern.



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keyboard divya

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