The mouse is an input device that usually contains one or two buttons. As a user moves the mouse on a flat surface, the mouse controls the cursor movement on the screen. When the user presses one of the buttons, the mouse either marks a place on the screen or makes selection from data or menu on the screen. A mouse has a sphere on its underside. This rotates as the mouse is moved along a flat surface.
The mouse translate the direction and speed of rotation into a digital signals that identifies the position or control, the cursor on the computer.
A mouse can be used for many application, ranging from games to drawing and designing products with computer graphics. It provides an alternative for people who are uncomfortable with a keyboard but it also can be used in combination with a keyboard to input data.
A Trackball is a pointing device almost like a mouse turned upside down. The user controls the cursor on the screen by rolling a plastic ball with a fingertip or wrist. To execute commands with a Trackball, one or more buttons are pressed, much in the same way as is done with a mouse. The cursor can be moved around on the screen by rolling the ball with a thumb or finger.
Trackball is popular among users of laptop computers when space is limited and may be mounted on either side of the keyboard. For handicapped people who may have difficulty pressing keys on a standard keyboard or using a mouse, the trackball may be the answer since it edoes not require to moves the entire arm to use it.
Scanner is an input device. It is also called Optical Reader or Digital Scanner. It scans or reads text and picture printed on a paper and enters them directly into the computer memory.
The advantage of a scanner is that the user needs not type the input data in. This is a lust and accurate method for entering data into the computer. The scanner takes electronic images, of text or pictures from the paper it breaks each image into light and dark dots and stores them into the computer memory in machine codes. Scanned text can be edited by OCR software. Optical Character Recognition (OCR) software translates the scanned document into text that can be edited.
The image scanner is useful because it translates printed images into an electronic format than can be stored in computer’s memory. The stored image can be transferred into a paint program or directly into a word processor. You can use software to organize and manipulate the electronic image.
A keyboard is the most commonly used input device which helps us in simply keying in required information in a computer. This information is subsequently stored in the computer’s memory. A keyboard can be used effectively to communicate with the computer but considered to be relatively slow as compared to other input devices. The keyboard is divided into following divisions:
These keys are similar to a standard typewriter and is used to type general information.
These keys are used to input numeric data only. These are very useful in case of large numeric data input because all numeric keys can be accessed by one hand only. These keys can also be used as an alternative to the screen navigation and editing keys.
These are keys marked as F1 – F12, located normally at the top of the keyboard. These are special keys provided to a programmer which allow him to attach special functions to each key. Each of these function keys are also given some special function in different packages.
SCREEN NAVIGATION AND EDITING KEYS
These keys are provided to move around in the screen. May programs use these keys to let the user move around the screen display. In some keyboards these keys are also provided inside the numeric keypad as alternate keys.
The description of commands assigned to function keys under the BASIC mode.
F1 – LIST Function – Used to display the lines of your 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 – COUNT Function – Used to restart a program after it has temporarily interrupted by a stop or CTRL + BREAK.
F6 – LPT1 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 number of program line to be displayed as these lines are executed.
F8 – TROFF Function – Refers to “trace off”. This function cancels TRON function.
F9 – KEY Function – Use to change the function of the other function keys.
F10 – SCREEN Function – Used to return program to the character mode from the graphic mode and a;so to turn off the colour.