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User Interface Design > Computer Factors > Flashcards

Computer Factors Flashcards

1
Q

What are the keyboard layouts?

A

QWERTY
DVORAK
Alphabetic keyboard

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2
Q

What are the characteristics of QWERTY keyboards?

A

Not optimal for typing
Result of the limitations of mechanical typewriters - needed to slow down the typist because typewriters could not keep up
Vast technological inertia

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3
Q

What are the characteristics of DVORAK keyboards?

A

Biased towards right handed people (56% of keystrokes are made by the right hand)
70% of keystrokes are made without the need to stretch far hence reducing fatigue and increasing keying speed

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4
Q

What are the characteristics of alphabetic keyboards?

A

Letters arranged alphabetically
No inherit advantages in this layout
Slows down touch typists

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5
Q

Describe chord keyboards

A

Letters are produced by pressing a combo of keys at the same time.
Usually 4-8 keys but can be bigger
Resistance by average user
Used by courtroom stenographers
Some versions are used for braille input with a refreshable braille display or voice synthesizer

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6
Q

What are the types of smart pencils?

A

Passive Stylus and Active Stylus

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7
Q

Describe passive stylus

A

They have no built in electronics, intelligence is built into the screen and OS. Limited in types of writing tools that it can emulate and it is more accurate than a finger.

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8
Q

Describe active stylus

A

It has built in electronics for touch sensitivity, memory, writing data, electronic erases etc. A large number of writing tools are emulated, it can detect types of strokes and amount of pressure being applied. And lastly they are wireless

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9
Q

What can be used for pointing and positioning?

A

Mouse
Trackball
Touchpad
Joystick
Touchscreens
Eye gaze
Stylus
Digitized tablet
Cursor keys

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10
Q

How does a mouse detect movement?

A

Using roller balls which have potentiometers which detect the direction in which the mouse is moving by sensing the movement of the ball

Via optical which uses infrared and lasers

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11
Q

How can the indirect nature of a mouse lead to hand eye coordination problems?

A

Because the mouse moves horizontally while the screen is vertical, you also have to lift the mouse to handle large screens and it’s quite difficult to use one in a 3D environment

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12
Q

What are the characteristics of a trackball?

A

It’s fairly accurate but hard to draw with since long movements are difficult. They are typically used by Repetitive Stress Injury sufferers as a replacement for the standard mouse.

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13
Q

What are the characteristics of a touchpad?

A

It’s found on most laptops, the finger speed can determine cursor distance.
A tap with a finger is equivalent to pressing the left mouse button and a hard press on the right side is a right mouse click.

Some utilize multi touch functionality

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14
Q

What are the characteristics of touch screens?

A

You can use a finger or stylus on them, meaning no mapping is required as in the case of the mouse.

They are generally intuitive to use
Due to the fact that you use a finger however screens get greasy marks.

It is fairly inaccurate, it’s poor for selecting small regions and moving on screen objects small distances and to an exact position.

Pointing to vertical screens also become tiring

Some utilize multi touch functionality

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15
Q

Why are touch screen laptops and monitors difficult to use?

A

Because the screen moves when pressed hard because of weak hinges on laptops.

It is less accurate than a mobile device

Mouse is more accurate than touch

Moving hand between keyboard and screen can be tiring

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16
Q

What are the characteristics of joysticks?

A

Movement is absolute
It is isometric (pressure corresponds to velocity of the cursor)
Very robust and inexpensive
Buttons are usually on the stick

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17
Q

What are the advantages of a stylus?

A

It has more accurate positioning on touch screens than fingers.

Means no greasy screens
It was popular with older PDAs/Handhelds

Increased use with mobile devices

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18
Q

What are the disadvantages of a stylus?

A

It is tiring to use on upright displays such as monitors

Switching between keyboard and stylus reduces usability

You can easily loose them. To reduce this devices use either magnets or inner slots to keep the stylus secured to the device

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19
Q

What are the characteristics of a digitized tablet?

A

It is used for free hand drawing
It is a more specialized device
It has high resolution and indirect mapping however it occupies a large amount of desk space

These have been replaced by touchscreens

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20
Q

What are the characteristics of eye gaze?

A

They may require special glasses, or a head mounted box, others have devices mounted on the screen.

They are fast and accurate
Not suitable for drawing since eyes don’t move in smooth lines
They can be expensive

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21
Q

What are the three types of digitized tablets?

A

Resistive tablets - detects the point contact
Magnetic tablets - detects current pulses in a magnetic field using a small loop housed in a special pen
Sonic tablet - pen emits an electronic pulse

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22
Q

What is the process of eye gaze in the past vs now?

A

Past -
low power laser is shone into the eye
The computer detects the reflected beam and needs calibration

Now-
modern devices use built in cameras to track movement

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23
Q

What are the characteristics of cursor keys?

A

They are available on most keyboards
Usually as four arrow keys
There is no standard layout but the most common is an inverted T

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24
Q

What are the different types of display devices?

A

LCD (Liquid Crystal Display)
LED (Light Emitting Diodes)
OLED (Organic Light Emitting Diode)

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25
Q

Describe a LCD

A

It uses fluorescent backlights

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26
Q

Describe a LED

A

These are LCD TVs which use light emitting diodes for the backlight. They are more energy efficient and have better display quality than LCDs.

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27
Q

Describe an OLED

A

These have no backlight because light can be emitted on a pixel by pixel basis without affecting each other.

They have the best colour production and contrast, are thinner and faster than other display devices however their displays are susceptible to image burn in.

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28
Q

What is frame rate?

A

Frame rate is how fast a monitor can display a frame of data

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29
Q

What is the difference between interlaced and progressive scan?

A

Interlaced is used by older devices, here the odd lines are displayed first followed by the even lines. On the other hand progressive scans are used by modern displays since they are so fast, the lines are displayed in sequence

30
Q

What does the p and i stand for at the end of the resolution?

A

P stands for progressive and I stands for interlaced

31
Q

How is positioning in a 3D space detected?

A

Using virtual controls and cockpit, a 3d mouse can also be used however it can lead to strain due to holding the mouse and arm in the air.

Datagloves are also used, these are a lycra glove with optical fibres this means when fingers bend, more light escapes and this is detected by ultrasound for the 3D position.

32
Q

What do virtual reality helmets and headgear do?

A

They display the 3D world to the eye. This also enables the position of the head to be detected which allows for a change of scenery, and to be able to change the position of an external object.

33
Q

How can VR perform whole body tracking?

A

BY covering your entire body in a special suit which has optical fibers which allows the device to use image processing

34
Q

What is a disadvantage of VR?

A

VR motion sickness since it has a slow response to head movement

35
Q

What do 3D displays use?

A

Visual effects such as shadows and stereoscopic vision such as small screens, polarized filters and blanked eye spectacles

36
Q

What is augmented reality?

A

A combination of the real world and computer generated content. It is used to enhance real world content with useful information and there are a variety of hardware devices but it’s most commonly found in mobile phones and tablets

37
Q

What are the display devices for augmented reality?

A

Specialized Glasses - Google glasses
Specialized headgear - Sony playstation VR headset
Mobile phones and tablets

38
Q

How does 3D work on a 2D display?

A

Using visual cues and the brain fills in the rest of the gaps. Attributes used are shading, shadows, size and positioning on the monitor

39
Q

Can 3D worlds be easily manoeuvred on a 2D screen?

A

No it cannot

40
Q

Why do mobile devices typically have two cameras?

A

A front facing camera to be used for video conferencing and a back facing camera to be used for taking pictures where its position facilitates that task

41
Q

What are the uses of cameras?

A

Taking photos and videos
Video conferencing
Augmented reality
Biometric based security (facial recognition)

42
Q

What determines camera quality?

A

Pixel density and speed. Alongside this many mobile devices come with software that enhances the camera ability e.g. removing unwanted things in a picture

43
Q

What is resolution?

A

The total number of pixels that a camera sensor can take. E.g. 12 MP is 12 megapixels

The higher the resolution the more detailed the image and less pixelation occurs

44
Q

What does sensor size determine?

A

The resolution and the size of the pixels.. The size of the pixel determines the amount of light that can be captured which matters in low light conditions.

45
Q

Is there a balance between resolution and pixel size?

A

Yes there is, for a specific size of sensor the more pixels you add the smaller the pixel which can lead to greater resolution but poorer quality in low light

46
Q

What is lens quality?

A

The quality determines how well the lens meets its expected properties, the resistance to scratches and the exclusion of visible flaws.

47
Q

What is aperture?

A

This is the opening that allows light into the camera. The wider it is, the better the photos. This is fixed on mobile devices but adjustable on regular cameras

48
Q

What is Image Signal processor (ISP)?

A

This is on mobile phones and tablets and it is responsible for processing the light information received by the sensor and converting it into the videos and photos stored.

49
Q

What are some functions of ISPs?

A

Noise reduction, lens error corrections and dealing with shaking of hands

50
Q

What are the two main storage formats of images?

A

RAW format and JPEG format

51
Q

Describe each storage format of images

A

RAW is the unprocessed version of the photo, all of the info captured by the camera is stored. Many manufactures use Adobe’s DNG format however RAW can consume up to 10-12 times the storage of JPEG files

JPEG is usually provided to convert RAW formats however information is lost

52
Q

Describe vibration in terms of mobile devices

A

Mobile devices vibrate to indicate and event has taken place such as a notification. These vibrations are caused by a miniature direct current motor

53
Q

Describe sound in terms of devices

A

Sound is generated using speakers, keyboard clicks and key presses on telephones however poorly designed sound use can cause stress

54
Q

How is touch implemented in devices?

A

Using haptic devices which provide force feedback, vibrations or using rising/smalling pins such as those on electronic braille devices

55
Q

Where does printing usually take place?

A

On paper, cardboard or related medium.

56
Q

What does resolution mean in terms of printing?

A

It measures the quality of the printing. The measure is dots per inch (dpi) where the more dots, the smoother the text looks

57
Q

What are the various types of printers?

A

Dot matrix
Inkjet
Laser printers
Bubble jet

58
Q

Describe dot matrix printers

A

It ranges from 80-120 dpi, to get a higher resolution it must pass over the text multiple times

59
Q

Describe ink jet

A

It ranges from 300-1440 dpi

60
Q

Describe laser printer

A

It ranges from 300-2400 dpi

61
Q

Describe bubble jet printer

A

It is the same as inkjet but more accurate and ink dries quickly (these are not common)

They are relatively quiet and used in printing photos because of their high quality

62
Q

What are other attributes of printing besides dpi and resolution?

A

Fonts which can have fixed pitch or variable pitch. Font selection is important because it determines how closely the font on the screen matches what is printed.

Screen and page, you want to achieve what you see is what you get however this is difficult because a screen’s dpi can be drastically different from the printer

63
Q

What must you consider when choosing a printer?

A

Cost of the printer, ink and maintenance
Speed of the printer
How long the ink lasts
Resolution required
Type of paper used
Work load requirements

64
Q

What are different types of scanners?

A

Flat bed
Hand held
Cameras on device

65
Q

What is used for scanning within scanners?

A

Optical Character Recognition (OCR)

66
Q

What is the max dpi for a scanner?

A

They can reach 4800+ dpi, more detail requires more storage space and choice of scanner depends on level of detail needed

67
Q

What are the various types of memory in computers?

A

RAM (Random Access Memory) which is short term memory (STM) and is non volatile in mobile devices

Disks which is long term memory (LTM) and this is seen in magnetic disks such as hard disk drives (HDDs), flash memory (USB flash drives and Solid State Drives (SSDs) and lastly optical disks such as CD and DVD

68
Q

What is the difference between STM and LTM?

A

STM is small and fast and LTM is large and slower

69
Q

What is the difference between HDDs and SSDs?

A

HDD capacities exceed SSDs however SSDs are more reliable, faster and power efficient. It is easier to recover data from HDDs than SSDs, HDDs are also cheaper than SSDs. Lastly SSDs are quiet.

The use of SSDs reduces the size and power demands in devices.

70
Q

When it comes to processing speed what are two main problems?

A

System is too slow and does not recognize input causing inaccuracies and system is too fast, something designed for a slower machine may end up too fast when placed on a faster machine

71
Q

What are the limitations on interactive performance?

A

Computation bound (indicate expected duration and progress)

Storage Channel bound (RAM Vs HDD/SSD)

Graphics bound (graphics operations take time and your device may need a graphics card)

Network capacity (speed of the network can affect the user experience)

User Interface Design (9 decks)

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