17_lesson.txt

Today is Sunday on September 3rd

lesson 17: page 24 and 25

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Joystick
Joystick is also a pointing device, which is used to move the cursor position on a monitor screen. It is a stick having a spherical ball at its both lower and upper ends. The lower spherical ball move n a socket. The joystick can be moved in all four directions.
The function of the joystick is similar to (that of) a mouse. It is mainly used in Computer Aided Design (= CAD) and playing computer game.

Light Pen
Light pen is a pointing device similar to a pen. It is used to select a displayed menu item or draw pictures on the computer screen. It consists if a photocell and an optical system placed in a small tube.
When the tip of a light pen is moved over the monitor screen and then pen button is pressed, its photocell sensing element detects the screen location and sends the corresponding signal to the CPU.

Track Ball
Track ball is an input device that is mostly used in notebook or laptop computer, instead of a mouse. This is a ball which is half inserted and by moving fingers on the ball, the pointer can be moved.
Since the whole device is not moved, a track ball requires less space than a mouse. A track ball comes to in various shapes like a ball, a button or a square.

Scanner
Scanner is an input device, which works more like a photocopy machine. It is used when some information is available on paper and it is to be transferred to the hard disk of the computer for further manipulation.
Scanner captures images from the source which are then converted into a digital form that can be stored on the disk. These images can be edited before they are printed.

*** new vocabulary ***
    joystick
    sphere, spherical
    light pen
    photocell
    socket
    photocopy