Computer:

“A computer is an electronic device that can accept data, process it and give results after that processing.”

To give output to computer and gets results some devices are required.

These devices are:

1. Output Devices.

2. Computer Input devices

1.Computer Input devices:

“The devices used in computer to enter data into a computer are known as Input devices.”

Examples:

Some of its examples are

1. Keyboard

2. Mouse

3. Joystick

4. Trackball

2.Output Devices:

“The devices that are used to extract data from a computer are known as Output devices.”

Examples:

Some of its examples are

1. Printers

2. Monitors

3. Speakers

4. Projectors

5. Plotters etc

Keyboard:

The Keyboard is the most common Computer Input devices and control device that is used with computers.The keyboard arrangement provide us standard on most keyboards is the “QWERTY” arrangement. Some of the most popular microcomputer offers enhanced “QWERTY” Keyboards designed for easy entry of numbers.

This is accomplished with a smaller group of keys known as “NUMERIC KEY PAD” at the right of the standard keyboard.

The keyboard allows communicating with the system unit through a dedicated keyboard port that contains both signal and power lines.

When a key is pressed, a signal for that character is generated and the character gets fed to the internal storage directly.

Upon the release of a key, depressing the different key sends a different signal.

Division of a Keyboard

A keyboard may be divided into four general areas.

1. Type writer area or Alphanumeric keypad

2. Numeric keypad.

3. Functional keypad

4. Screen navigation and Editing key

1.Type writer/Alphanumeric keypad: -

Keys in this area are used to enter general information into the computer. Key positions in the typewriter area are the similar to those on a typical typewriter.

It consist of a

a. Alphabet keypad.

b. Number keys.

c. Punctuation keys.

a. Alphabet keypad:

Alphabet keypad consisting of keys A to Z.having upper case and lower case letters.

b. Number Keys:

The keys having numbers from 0 to 9 are called number keys.

c. Punctuation Keys:

Special keys and space bar keys are known as punctuation keys.

2.Numeric Keypad: -

On the right of the central body there is a set of keys similar to that of calculator. These are dual-purpose function keys that can be used for rapid numeric data entry or editing and cursor control.

3. Function keys: -

These are 10 or 12 function keys labeled as

F_1,F₂,…………………………. F₁₀ or F₁₂

These are located on the left or at the top of the keyboard. Function keys define the system or application programs being executed. These are used to instruct the computer to perform certain commands. These keys provide short cuts for doing routine tasks on a computer.

Under “BASICA” (Advanced Basic)

These function keys can be used as

a. Soft Keys: -

That is you can get each key to type any sequence of characters. Some frequently used commands have already been used to assign to these keys. How ever these commands cannot be changed through the key statement.

b. Program Interrupts: -

In “BASICA” through the use of ONE KEY statement.

Below is the description of commands assigned to function keys under the BASIC mode.

KEYS	BASIC FUNCTION	FUNCTION
F₁	List Function	Used to display the lines of yours program on the screen.
F₂	Run Function	Used to execute a program from its beginning.
F₃	Load Function	Used to read a program from a storage device and store it in main memory
F₄	Save Function	Used to store a program on a storage device from memory
F₅	Cont Function	Used to restart a program after it has been temporarily interrupt by a stop or CTRL break.
F₆	LPT 1 Function	Used to transfer data from the video screen to the line printer
F₇	TRON Function	Refers to “trace on”. This function causes the line numbers of program lines to be displayed as these lines are executed.
F₈	TROFF Function	Refers to “Trace off’ this function cancels TRON function.
F₉	Key Function	Used to change the function of the other function keys.
F₁₀	SCREEN Function	Used to return program to the character mode and also to turn off the color.

Function keys perform different tasks in different software packages. The commands assigned to the function key in windows made are given below.

FUNCTION KEYS IN WINDOWS MODE
F₁	Get on line help or the office assistant.
F₂	Move text or graphic.
F₃	Insert an auto text entry.
F₄	Repeat the last action.
F₅	Choose the GO TO command (Edit Menu)
F₆	Go to next frame.
F₇	Choose the spelling commands (Tool Menu)
F₈	Extend a selection.
F₉	Update selected fields.
F₁₀	Activate the menu bar.
F₁₁	Go to the next field.
F₁₂	Choose the save as commands (File Menu)

The function keys in Windows can also be used in combinations with one or more other keys such as SHIFT, CTRL, and ALT.These combinations are the short cuts to carry out certain commands.

For Examples: -

SHIFT+F2: -

Copies the text.

CTRL+F2: -

Choose the print preview

4. Screen Navigation/ Editing keys: -

Four cursor control keys are used to move the cursor on the screen in the direction shown by the arrows on these keys.

In addition these are special keys for doing special job and editing.

These are: -

a. ESC key

l. INSERT key

m. DELETE key

n. MINUS key

o. PLUS key

p. CURSOR CONTROL key

q. CURSOR key

r. HOME key

s. END key

t. PAGE UP key

u. PAGE DOWN key

Tab key

c. CTRL key

d. SHIFT key

e. ALT key

f. BACK SPACE key

g. ENTER key

h. PRT.SC.key

i. CAPS LOCK key

j. NUM.Lock key

k. SCROLL lock key

a. Esc key: -

Esc key perform a variety of functions defined by the operating system.

b. TAB key: -

Perform a TAB function as on typewriter.

c. CTRL key: -

Perform a command or function when used in conjunction with another key.

d. SHIFT key: -

Used to change lower case letters to capitals and vice versa. All other things when pressed with shift cause the character shown on the upper portion to be displayed.

e. ALT key: -

Alternate key with alpha typing keys enter BASIC key word. A SCII code can also be entered using the Alternate key.

f. BACK SPACE key: -

Moves the cursor one character to the left and erases the character in that position, whenever the key is pressed.

g. ENTER key: -

Moves cursor from the final position on a line to the first position on the next line.

h. PRT.SC.key: -

Print screen key when used with shift prints a copy of the information on the screen.

i. CAPS lock key: -

When pressed one, locks the character A to Z in the upper case position or in the Block letters of alphabets from A to Z.Press it again to get the lower case position or small letters or alphabets.

j. NUM. Lock key: -

Pressing the number lock key once places key 0 to 9 in numeric mode. Pressing it again returns into cursor control. It gives green signal on its place when it is pressed which the signal is switched off or disappears when it is again pressed.

k. SCROLL lock key: -

This key is defined by the operating system of our computer or it can also be defined by the application programmed.

l. INSERT key: -

Press it once and you can insert letters in the middle of already written two characters. Press it again and it returns to the normal (over write) mode in which the mode was already present.

m. DELETE key: -

The characters at the cursor position are deleted.

n. MINUS key: -

Enter minus on the display.

o. PLUS key: -

Enter plus on the display.

p. CURSOR CONTROL key: -

(Number lock released).

q. CURSOR keys: -

Four cursor keys move the cursor up, down, left and right.

r. HOME key: -

The HOME key moves the cursor up, down, to the first character position in the top line of the screen.

s. END key: -

The end key moves the cursor to the final position of the line.

t. PAGE UP key: -

Page up is program-controlled key used to move the cursor to the previous page.

u. PAGE DOWN key: -

Page down is also a program-controlled key. It is used to move the cursor to the next page

TYPES OF KEYBOARD

There are two basic styles of keyboard commonly found with microcomputer.

1. PC/XT. STYLE KEYBOARD

2. AT-STYLE KEYBOARD

1. PC/XT. STYLE KEYBOARD: -

This keyboard was first one develop by IBM. Later the other type or style of keyboard.

2. AT-STYLE KEYBOARD: -

AT-Style keyboard was developed with slightly different keyboard having 101 keys. Different manufacturing has developed different keyboard with different styles but same function slight alternation with keys ranging from 84 to 108 using different styles.

SPECIAL FUNCTION KEYBOARD

Some keyboards are designed for specific applications

For Examples: -

The cash registers like terminals at most fast food restaurants have special purpose keyboards. Rather then key in the name and price of an order of French fries attendants need only pressed the key marked. “French Fried” to record the sale. Such keyboards help shop supervisors to save their time and interact more quickly with their computers.

Mouse:

POINT AND DRAW DEVICES: -

The effectiveness of Graphical User Interface (GUI) depends on the users ability to make a rapid selection from a screen full of graphic icons or menus.

In these instances the mouse can position the pointer over an icon quickly and efficiently. Computers artist use mouse to create images. Engineers use them to draw a line that connects points on a graph.

MOUSE: -

A mouse is an Computer Input devices unlike the keyboard information is typed, mouse is a pointing device and to select the various operations.

CONSTRUCTION: -

A mouse consists of a small hand held unit with one, two or three buttons and a small ball at the bottom on which it can roll.

ATTACHMENT WITH COMPUTER: -

The mouse is either attached to the computer by a cable or linked via wireless remote connections. All movements of the mouse are reproduced by the graphics cursor on the screen.

WORKING: -

As the mouse is moved across the desk on a mouse pad, it guides a small locator symbol (often an arrow, a cross hairs, or a cursor), which moves across the screen of our monitors.

A typical mouse with proper soft ware can also be used to draw pictures on the screen and edit text.

To use mouse, you combine pointing with four techniques.

CLICKING

DOUBLE CLICKING

DRAGGING

RIGHT CLICK

Most mice operator with a ball that spins and set of rollers. If the mouse does not operate properly, you can clean it by removing the cover plate and ball and removing debris.

For Example: -

When you move a mouse up and to the right the graphics cursor moves towards the top right hand corner of the screen. Use the mouse for quickly operating the graphics cursor.

TRACK BALL: -

A track ball provides the functionality of the mouse but requires less space on the desktop. Instead of moving the entire unit to roll the ball against the desktop, the unit sits still and you move the ball with your fingers.

TRACK PAD: -

A track pad provides the functionality of the mouse but requires less space and less movement. You use a track pad by dragging your fingers across it touch-sensitive surface.

It is hard to believe that many users once scoffed at the notion of using a mouse with the computer. But with the advent of

Graphical user Interface, such as the MACINTOSH operating system, windows and some versions of UNIX.

The mouse became an Computer Input devices because it enabled user’s to issue commands and choose options for menus and graphical toolbars instead of typing them.

Today, some users such as graphic artists and designer’s rely more on the Computer Input devices mouse then their keyboards.

Students Projects and Assignments

Tuesday, February 8, 2011

Computer Input devices

Division of a Keyboard

1.Type writer/Alphanumeric keypad: -

It consist of a

These are 10 or 12 function keys labeled as

FUNCTION KEYS IN WINDOWS MODE

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