HOW CAN WORK THESE IMPORTANT FUNCTIONS

TRACKBALL

The user controls the cursor on the screen by rolling a plastic ball with the fingertip or wrist. To execute commands with a trackball, one or more buttons are pressed, much as is done with a mouse. To move the cursor around the screen you roll the ball with your thumb or finger. Because you dont't move the whole device, a trackball requires less space than a mouse, so trackball is a solution when space is limited and is popular among users of laptop computers. Trackball may vary in size, but most are approximately the size of a standard desk calculator and may be amounted on either side of the keyboard. For handicapped people who may have difficulty pressing keys on a stadard keyboard or using a mouse, the trackball may be the answer since it is not necessary to move the entire arm to use it.

ELECTRIC LIGHT PEN

It consists of a photo cell placed in a small tube which can sense a position on displau tube when the end of the pen is held against the screen. In specially designed display seceen, data can be entered with a light pen as shown. When this electric light pen is brought near the screen, the light emitted is sensed by the photo cell. The electrical response is communicated to the computer to determine the part of the displayed item which is exciting the photo. A spot appears on the display screen at the location determined by the position of the pen. A computer programme compares the dot position generated by the device with computer generated data.. In this way new data can be entered or existing data can be modified figure below shows the use of a light pen in conjunction with a graphic display terminal to enter information into the computer. There are many other input devices like video digitizer, voice recognizer, magnetic ink character reader (MICR), optical character reader (OCR), remote terminal used for E mail, graphic table, etc. which can be linked with the computer. This is the most exciting part of using a personal computer.

DIGITAL CAMERA

Digital cameras operate on the same basic principles as a basic camera, but are more suitable for desktop publishing. The primary difference between a basic camera and a digital camera is that they use different media capturing images. The traditional camera uses film, while the digital camera uses a charged coupled device (CCD). Once captured, images can be uploaded to a PC and used in countless applications.

TRACKBALL, ELECTRIC LIGHT, DIGITAL CAMERA