Operation Of Mouse And Keyboard Computer Science Essay

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The main goal of a mouse is to translate the motion of ones hand into signals that a computer can interpret to operate on the screen. There a several types of mice: mechanical mice, optical mice, wireless mice, and track-ball mice. Each of these work in a similar way, by using sensors to detect movement, which is then translated into information that the computer can interpret.

A mechanical mouse uses rollers that touch the ball. One of the rollers is oriented so that it detects motion in the X direction and the other detects motion in the Y direction. When the ball rotates, the rollers rotate also. The rollers connect to a shaft that spins a disk with holes in it. On either side of the disk is a LED and an infrared sensor. The holes in the disk break the beam of light coming from the LED so that the sensor sees pulsing light. The rate of pulsing light is related to the speed of the mouse and distance it travels. Inside the mouse is a processor chip. This reads the pulses from the sensors and turns them into binary data the computer understands. The chip sends the binary data to the computer through the mouse's cord.

An optical mouse uses LED light. First, the LED produces a red light that is emitted onto a surface. The light is reflected off of the surface back to the CMOS sensor. The CMOS sensor sends each image that is reflected back to a digital signal processor. Using the thousands of images that the CMOS sends to the digital signal processor for analysis, the DSP is able to detect both patterns and images and can determine if the mouse has moved, at what distance it has moved, and at what speed. The DSP can determine coordinates that are then sent to the computer that the mouse is hooked up to. The computer receives the coordinates and will show the mouse's movement. A computer is updated with mouse coordinates more than hundreds of times per second. Because movement is so fast, the mouse appearance on the screen doesn't reflect the updating of coordinates and thus, movement is very smooth.

Wireless mice use radio frequency technology to communicate information to your computer. Being radio-based, RF devices require a transmitter and a receiver. The transmitter is housed in the mouse. It sends an electromagnetic signal that encodes the information about the mouse's movements and the buttons you click. The receiver, which is connected to your computer, accepts the signal, decodes it and passes it on to the mouse driver software and your computer's operating system. The receiver is usually a separate device that plugs into your computer and is about the size of a nickel.

The standard PS/2 mouse sends movement and button information using the following 3-byte packet.

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Byte 1

Y overflow

X overflow

Y sign bit

X sign bit

Always 1

Middle Btn

Right Btn

Left Btn

Byte 2

X movement

Byte 3

Y movement

The movement values are 9-bit 2's complement integers, where the most significant bit appears as a "sign" bit in byte 1 of the movement data packet. Their value represents the mouse's movement relative to its position when the previous packet was sent.

If a mouse supports the scrolling wheel, it requires a 4-byte movement data packet rather than the 3.

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Byte 1

Y overflow

X overflow

Y sign bit

X sign bit

Always 1

Middle Btn

Right Btn

Left Btn

Byte 2

X movement

Byte 3

Y movement

Byte 4

Z movement

"Z" movement is a 2's complement value that represents the scrolling wheel's movement since the last data report.

A mouse has four modes of operation: Reset, Stream, Remote, and Wrap. Reset is the initial mode, in which the mouse performs initialization and self-diagnostics. Stream is the mouse's operating mode. The mouse issues movement data packets when movement occurs or when buttons are pressed. Remote is when the host must poll for movement data packets and wrap is a diagnostic mode where the mouse echoes every received packet back to the host.

A mouse enters reset mode upon power-on. The mouse performs a self-diagnostic test by setting the following default values: Sample rate = 100 samples/sec, Resolution = 4 counts/mm, Scaling = 1:1, and Data Reporting = disabled. The mouse then sends a completion code of either 0xAA (successful) or 0ZXFC (error). Following the completion code, the mouse sends its device ID of 0X00. This distinguishes it from a keyboard. Once the mouse has sent its ID, it enters stream mode.

In stream mode the mouse sends movement data when it detects movement or a change in state of one or more mouse buttons. The maximum rate at which this data may be reported is known as the sample rate. This parameter ranges from 10-200 samples/sec, with a default value of 100 samples/sec.

In remote mode the mouse reads its inputs and updates its counters at the current sample rate, but it does not automatically issue data packets when movement has occurred. Instead, the host polls the mouse using the "Read Data" (0xEB) command. Upon receiving this command the mouse will issue a single movement data packet and reset its movement counters.

Part 2: Operation of a Keyboard

To open Internet Explorer using the keyboard is just as simple as using the mouse. Using a few simple key strokes and a user can have access to Internet Explorer. The process to access Internet Explorer is one would press the key “I” until the Internet Explorer is highlighted and then the enter key should be pressed. Now that Internet Explorer is open one can also use key strokes to operate it. The first step one needs to apply would be the key stroke CRTL+O. This will open a URL box in which one can type the destination that they would like to access then the ENTER would need to be selected. To toggle between full-screen and other views in the browser the user would need to press F11. To move forward through the items on a Web page, the Address box, or the Links box the TAB key would need to be applied by the user. If a user would want to return to their home page the key stroke that would be applied is ALT+HOME. To go to the next page the ALT+RIGHT ARROW would be applied and to go to the previous page the key stroke would be ALT+LEFT ARROW. If the user would like to scroll toward the end of the web page, the down arrow would be applied, and to scroll towards the top of the page the left arrow would be applied. To move to the beginning of the page the user would apply the HOME key and the move to the end of the document the END key needs to be applied. To find a certain matter on a page the key stroke the user would apply the CRTL+F keys. Here are a few other useful keys a user could use. CTRL+N which opens a new window, CTRL+W which closes the current window, CTRL+P will print the current page, and to save the current page the user would select the CTRL+S keys. Internet Explorer can be solely operated with the use of a keyboard if the user knows the correct key strokes and combinations.

For a user to access Microsoft Office Word 2009 the same process would be applied. The “M” key would be applied, and then the ENTER key would be selected. Once the user has Microsoft Word open, it can be fully operated without the use of a mouse. A lot of the same key strokes and selections for Word are the same as Internet Explorer. For the user to open a new document they would need to select the CTRL+N keys. To select all the information in a document the user would select the key strokes CTRL+A, but to select a certain section of a document the user select CTRL+SHITFT+ LEFT ARROW or RIGHT ARROW depending on the direction the user would like to go. If a user would like to switch between documents, select and copy certain itext, and then paste it in another document there is a series of key strokes the user would need to select. First to transfer to another document the user would select CTRL+F6. Once in the document that contains the text that would like to be selected the user would scroll using the LEFT, RIGHT, UP, or DOWN ARROW until the destination is reached. Once there the user would select the CTRL+STIFT+ LEFT or RIGHT ARROW to select the text desired. After, the text is select the user would apply the CTRL+C key strokes which copies the selected text. The user would then need to select CTRL+6 until the document that the user desires to paste the text is reached. The user would select CTRL+V which will paste the text in the document. CTRL+F4 will close the window. CTRL+F12 will choose the Open command in which the user can type the name of a document that they wish to open. To save a document the user would need to select the SHIFT+F12 key stroke. Those are the most commonly used task in Microsoft Office word that a user would have been done with a mouse.

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