The ball-style computer mouse is a hand-operated device that lets you control more easily the location of the pointer on your screen. You can make selections and choices with the mouse button.

This type of mouse contains a rubber-coated ball that rests on the surface of your working area or a mousemat. When the mouse is moved over that surface, the ball rolls.

The ball's movements up and down, and left and right, turn the two axles inside the mouse. As they run, detectors register the changing position. A small integrated circuit inside the mouse sends signals to the operating system, which instructs it to move the pointer on the screen.

Inside an optical computer mouse

An optical mouse is much more hi-tech than a ball mouse. Where a ball mouse has quite a few moving parts, an optical mouse is almost entirely electronic (it has almost no moving parts). Here's the inside of a typical optical mouse and a few of the main components. The most interesting bits are in the center (where the LED light shines down onto your desk) and at the front (where button presses are detected by switches): Components inside a low-cost optical mouse:

1. A LED at the back generates red light and shines it horizontally, from the back of the mouse toward the front (from the left to the right of this photo).
2. A plastic light guide channels the light from the LED at an angle, down onto the desk.
3. A light-detector chip measures light reflected back up from the desk, converting the analog movements of your hand into digital signals that can be sent to your computer.
4. The scroll wheel at the front of the mouse is mounted on a switch mechanism that detects both how much it's rotated and whether you've pressed it (it functions like the central button of a conventional mouse). Rotations of the scroll wheel can be detected in a variety of different ways. Some mice use potentiometers (broadly, variable resistors), similar to the volume control on a radio but able to turn around multiple times. Others use various kinds of rotary switches or optical (rotary) encoders to convert analog wheel movements to digital signals.
5. A microswitch detects when you press the right mouse button. There's an identical switch on the other side to detect the left mouse button.
6. The USB cable connection carries digital information from the mouse to your computer.

Grammar Focus 01: Revendo o Simple Present (Presente Simples)

Estude estas orações sobre as teclas e o mouse óptico.

1 This key moves the cursor down.
2 This key copies the screen display.
3 This key doesn't have a fixed function.
4 A LED at the back generates red light and shines it horizontally, from the back of the mouse toward the front.
5 The USB cable connection carries digital information from the mouse to your computer.
6 An optical mouse has almost no moving parts.

Grammar Focus 02: O que são os MODAL VERBS?

São verbos auxiliares que expressam atitudes do falante. Por exemplo, os verbos modais podem expressar que um falante sente que algo é necessário, aconselhável, permissível, possível ou provável. Além disso, eles podem expressar a intensidade dessas atitudes.

1. Diferente dos verbos vistos acima (Grammar Focus 01), os verbos modais NÃO levam -s quando o sujeito é he, she, it.
CORRECT: She can do it. (Ela consegue fazer isso.)
INCORRECT: She cans do it.

2. Os modais são seguidos imediatamente pela forma básica de um verbo (sem to).
CORRECT: She must do it. (Ela deve fazer isso.)
INCORRECT: She can to do it. / She can does it. / She can did it.