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1 - Theory of Computer Science / Input Devices (Manual)
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Input Devices
Input devices (and output) are things what we all take for granted with regards to the functionality of computers. Without both Input and output devices, our computers would be useless... after all what could you do without a mouse keyboard or monitor??
An input device is a piece of hardware that allows the transfer of data from the outside (Real) world, into the computer. Essentially it allows he user (or sometimes environment) to IN PUT information into the computer.
An input device is a piece of hardware that allows the transfer of data from the outside (Real) world, into the computer. Essentially it allows he user (or sometimes environment) to IN PUT information into the computer.
Manual Input Devices
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What is an Input device?
An input device is a piece of hardware used to transfer data from its source into the computer. Manual input devices are ones that require human intervention to work correctly. Manual Input devices include but are not limited to the following:
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Pointing Devices
Pointing Devices are important tools which allow users to navigate computer systems usually by controlling a pointer.
There are two types of pointing device that we need to be aware of, these are the Tracker ball and the Mouse.
There are two types of pointing device that we need to be aware of, these are the Tracker ball and the Mouse.
Trackerball
Trackerballs are devices that simply put, have a ball on top which the user can move with the palm of their hand, as the ball moves it will turn rollers inside the device which allow the computer to interpret movement and move the pointer on screen.
Why use a trackerball?
There are a few reasons why you may use trackerballs over a mouse.
Reason 1 - People with disabillities restricting arm, wrist or finger movement will find it easier to use than a mouse.
Reason 2- There may be situations in which desk space is limited e.g.a busy factory or a shopping mall information center, here there would be no room to have a mouse dangling around.
Why use a trackerball?
There are a few reasons why you may use trackerballs over a mouse.
Reason 1 - People with disabillities restricting arm, wrist or finger movement will find it easier to use than a mouse.
Reason 2- There may be situations in which desk space is limited e.g.a busy factory or a shopping mall information center, here there would be no room to have a mouse dangling around.
Mouse
Everyone should be familliar with what a mouse does but perhaps not everybody would be aware of the different typesof mouse and how they work.
There are two types of mouse, these are Optical Mice and Mechanical Mice.
There are two types of mouse, these are Optical Mice and Mechanical Mice.
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Optical Mice
An Optical mouse has a red LED and a sensor underneath. As the mouse is moved around by the user, the way in which the light reflects back to the sensor will change thus allowing the processor to determine how the mouse is moving. This detected movement can then be transferred to the pointer on screen. |
Mechanical Mice
A Mechanical mouse will have a rubber ball underneath it. when the mouse is moved around by the user, the ball will cause rollers to rotate, the processor can then use the movement of the rollers to calculate the movement of the mouse and will cause the on screen pointer to move accordingly. |
Keyboards
Keyboards are hardware devices that allow users to press on physical keys that will allow them to input letters or characters into a computer system.
How does it work?
How does it work?
- Each of the keys on a keyboard has a small peg underneath it. When the key is pressed, the peg fits perfectly into a small hole.
- Once the peg fits through the hole it makes contact with a conducting membrane, pushing it past an insulating layer to make contact with a second conducting layer. This completes the circuit, depending on where the layers make contact will determine what electrical signal is sent to the microprocessor. This signal is read as binary and the ASCII table is used to present to correct letter to the user.
Touch screens
Touch screens are actually one of the few devices that are both input (Pressing the screen) and output (displaying information).
There are 4 different types of touch screen that you should be aware of, these are:
Resistive
Capacitive
Surface Acoustic Wave (SAW)
Infrared
There are 4 different types of touch screen that you should be aware of, these are:
Resistive
Capacitive
Surface Acoustic Wave (SAW)
Infrared
Resistive Touch Screens
How do they work?
Resistive touchscreens are made with two layers, the top layer that the user touches is made from polyester and underneath this layer is a glass layer.
When the user touches the top layer (polyester) it will bend and make contact with the glass layer, this completes a circuit.
The position of the touch on the screen is calculated by a microprocessor based on where the circuit was completed.
Advantages:
Disadvantages:
- Resistive screens allow for the use of a stylus
- It is possible to use whilst wearing gloves
- It is a cheaper technology than other touchscreen types
Disadvantages:
- Multi-touch is not possible
- Average durability - Easily scratched
- Poor visibility in bright sunlight
Capacitive Touchscreens
How do they work?
Capacitive touchscreens are made with many layers of glass, these glass layers act like capacitors that create an electric field between the glass.
When a person touches the top layer of glass their finger will change the electric current between the glass layers, the coordinates of where the current changes is sent to a microprocessor that uses the information to calculate where the touch happened.
Advantages:
Disadvantages:
- Medium cost - more than resistive but less than others
- Multi-touch is possible
- Very durable - A lot of force is required to break the glass
Disadvantages:
- Capacitive touchscreens only allow touch to be made with bare fingers, gloves will not work as it will affect the electricity. (Some special stylus are available)
Infra-red Touchscreens
How do they work?
Infra-red touch screens work by creating a grid pattern using LEDs and photocells (light sensors)
LED lights shine constantly across the screen and into its corresponding sensor
When somebody touches the screen, the light is blocked and certain sensors will recognize that they no longer detect light.
A microprocessor will use this information from the sensors to calculate the coordinates of where the touch was made.
Infra-red touch screens work by creating a grid pattern using LEDs and photocells (light sensors)
LED lights shine constantly across the screen and into its corresponding sensor
When somebody touches the screen, the light is blocked and certain sensors will recognize that they no longer detect light.
A microprocessor will use this information from the sensors to calculate the coordinates of where the touch was made.
Advantages:
Disadvantages:
- Multi-touch is possible
- Bare fingers and stylus can be used
- Good screen durability
Disadvantages:
- It is Expensive
Surface Acoustic Wave Screens
How do they work?
SAWs work similarly to Infra red screens, however, instead of creating a grid of light, it uses a grid of sound waves.
Two sound wave transducers generate ultrasonic waves and two receivers are used to receive the sound.
When the screen is touched, the sound wave is interrupted and will not reach the receiver. This information is sent to the microprocessor and used to calculate the coordinates of the touch.
SAWs work similarly to Infra red screens, however, instead of creating a grid of light, it uses a grid of sound waves.
Two sound wave transducers generate ultrasonic waves and two receivers are used to receive the sound.
When the screen is touched, the sound wave is interrupted and will not reach the receiver. This information is sent to the microprocessor and used to calculate the coordinates of the touch.
Microphones
Microphone are hardware devices designed input analogue sound waves into a computer as digital signals.
How does it work?
How does it work?
- A sound wave will be directed at a microphone
- The sound wave will cause the diaphragm inside the microphone to vibrate forwards and backwards
- This causes a coil to vibrate which in turn changes the magnetic field produced by a magnet
- Changes in this current are detected and a signal is output
