Computer Input Devices Most Important

INPUT DEVICES

Computer data and instruction a entered into a computers through inputs devices a input devices convert input computer data and instruction into a suitable devices of computer binary form an which is stored computers in the memory of a computers of many computer uses

The most commonly used input device is the keyboard A number of other input devices, also known as pointing devices of computer, have also been developed which do not require data entry by typing. Examples include mouse, light pen. Graphic tablet, joy stick. Track ball, touch screen, etc. Each of the devices permit the user to select something on the monitor screen by pointing to it Therefore, these devices are also called pointing devices. Voice input systems have also been developed. A  microphone similar to the one used with a public address system is used for voice input.

Keyboard          

Programs and data are entered into a computer through a keyboard which is attached to a computer. A keyboard is similar to the keyboard of a typewriter It contains letters, digits, special characters, function keys and some control keys, When a key is pressed, an electronic signal is produced which is detected by an electronic circuit called keyboard encoder (see Figure 2.8)

A computer includes all the keys found on a typewriter plus some additional keys These additional keys are cursor control i.e., moving the cursor around on the screen) insert, delete, and scroll control keys There are a total of 101 keys sme have more At the right side of the keyboard is the numeric keypad with numbers and basic mathematical symbols.

The numeric keypad can also be used for cursor control This double function of numeric keypad is controlled by the Num Lock Key.

At the top of the keyboard are function keys F1 to F12 Their functions depend upon the program being run.

The keyboard contains a small built-in processor. When you press a key, this processor detects it and sends a number binary number corresponding to that key scan code to the keyboard controller, located on the motherboard This code is transmitted to the processor CPU then processes it using a program called keyboard driver. The keybard driver translates the codes into their corresponding characters. 

Standard Typewriter Keys

A PC keyboard has a set of keys that closely resemble the keys found on a typewriter. These include the numeric keys (0 to 9),character keys (A to Z)

And special character keys (!,@#,$,etc.) The keys of the keyboard are often called QWERTY keys (named after the top row of letters).

Function Keys

Keys labeled as F1 to F12 carry out special functions in the software running in the PC. For example, the F1 key in most programs displays the help file available for using that program.

Cursor Movement Keys

These arrow keys are used to move a cursor a blinking line on the monitor to the left, right, pu or down respect tively In addition there are four more keys pg up pg dn Home and end these keys move the cursor quickly through the text the Home and end keys are specially used for positioning the cursor at the beginning and at the end of the text, respectively. In the case of the 101 keys model of the keyboard there is a separate set of cursor movement keys, namely, arrow keys.

Special Purpose Keys

Backspace Key The backspace key erases a character immediately to the left of the cursor.

Enter Key or Return Key The key also called the Return key on a keybard is used to indicate the end of a line or a paragraph it is also used to indicate the end of the command given to a computer to enable it to execute the instruction.

Esc Key The Escape key is used to instruct a PC to cancel the command just given.

Shift Key When you press and hold the shift key and type lower case a you get an upper case A on the screen as in the case of a typewriter However if the caps lock key is ON this effect isreversed whre there are two symbols or characters typed by a key holding down the shift key causes the upper symbol of character to appear For example in the case of number keys you find tow characters marked on every key Holding down jthe shift key and pressing the number key causes the causes the upper symbols, such as ~!@#$%, etc., to appear on the csreen.

Caps Lock Key the caps lock key is a toggle when pressed tor the first time, all letters will be typed in upper case (e.g., a will be typed as a) If you press the caps lock key again, all letters will be typed in lower case Press the caps lock key to type a letter in upper case.

Tab Key – Pressing the tab key, you can position the cursor at the preset position of 5 spaces of more on the screen. The key also helps in typing table text The function of this key is very similar to that of the tab key used in a typewriter.

Ins Key – Ins is the short from for Insert The key works both in insert and overstrike modes Once you press the key and type the text or characters from the keyboard the new text moves the previously typed text to the right This is called insert text mode If you press the ins key again and type, the newly typed text will overwrite or erase the previously written text on the screen this is called overstrike mode when you type in overstrike mode, the typed text overwrites the text at the cursor position with the new text.

Delete Key – By pressing the del key you can erase the character appeaing just above the cursor You can also use this key to the character where the cursor is The cunction of the del key is different from the of the backspace key the backspace key deletes the character to the left of the cursor whereas the del key deletes the character above the cursor.

Print Screen If you press the prt sc key and the shift key together the text displayed on the screen will be printed on your printer connected to the computer.

Multi-Key Combination

A multi key combination is a combination of two or more keys that you press together at the same time for example to type sushma you would press the shift key and then type s key to get upper case s most key combinations use either ctrl of alt keys Ctrl is a short most key combinations use either ctrl or alt keys ctrl is a short form for control and alt is for alternative thus to perform the ctrl c key combination  you would press and hold the ctrl key along with the c key the job done by a key combination depends upon the program that is being run for example, pressing the ctrl alt del key combination will reboot or restart your pc.

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