|
AC303/AC507 Notes 3 |
User Interface Styles and Support 1
Input
User Interface
The user interface is all the parts of the computer system that the user
has contact with, through touch, sight or sound.
Examples:
Screen, data on screen, keyboard, mouse, user manual, training.
The interface should be designed so that the user can carry out tasks
effectively and efficiently. A poorly designed interface can lead to loss
of productivity, numerous errors and a fair amount of user frustration.
Most interface designs are flawed and human users end up finding ways of
coping with these flaws (another computer wouldn’t tolerate such
design faults!).
Input is entering data and commands into the
computer system. When considering how this is to be done, the designer
should look at all the choices available.
Choice of Limb - the
user can input data and commands with fingers, whole hands, arms and feet.
Type of Control - the control can be a keyboard, push button, slider,
wheel, etc.
Method of Operation - what does the user do with the
control? Pull it? Push it? Turn it?
Position of the Control - the
designer has to decide where it will be, left, right, middle or back of
the keyboard or control panel.
Label - what does the control do, the
user needs to know.
Feedback of Operation - the user needs to know
that the operation has worked (or otherwise).
Input Devices
Input devices are what the user controls to give data and
instructions to the computer. The software transforms these into a form
the computer can process. There are a variety of input devices that
present opportunities and challenges to the system designers, but it is
important to select the most appropriate one for the user, the task and
the environment.
Examples:
A numeric keypad for telephone
numbers, but a typewriter keyboard for text.
A speech input device
would be most appropriate for people with arthritis, or where the user’s
hands are busy.
In order to ensure that the input device adds
to the success of the system, designers must look at these factors and
consider the underlying issues such as speed, accuracy, fatigue, user
satisfaction, etc.
Input Devices
Keyboard
The
keyboard is still the most commonly used input device. Most computer
keyboards are based on the key layout of typewriters (remember the
typewriter?). Most of us are familiar with the QWERTY keyboard with which
alphanumeric (words and numbers) data can be input rapidly by trained
people. For a standard data entry keyboard, there are two alternatives to
QWERTY. The Dvorak keyboard is designed for more efficient input, but
would require retraining for QWERTY keyboard users.
Example:
The Dvorak keyboard is reckoned to reduce finger travel from 12 - 20 miles
per 8 hour day to a little over one mile per day.
There is also
the alphabetic keyboard which has the keys arranged in alphabetical order.
This was designed for efficient input for non-trained users but, in
practice, has proved no faster than QWERTY or Dvorak.
Other keyboards
used for specific purposes are chord and numeric. One type of chord
keyboard is used to record transcripts of court and parliamentary
proceedings. Several keys are pressed simultaneously and the words are
formed in short-hand type notation. Text can be entered very rapidly using
these keyboards (200 w.p.m.), but much training is required to both input
data and read the output. The piano is also a “chord” keyboard
and is used to enter data into music synthesisers in a natural manner.
Numeric keypads are used by both trained and untrained users to quickly
key in numeric data. As well as numbers, it also has operator keys (plus,
minus, multiply, divide), a decimal point key and an enter key.
Examples:
Telephone, calculator, Automated Teller Machines
Keyboards also have special function keys which perform actions rather
than just enter data. Some of the function keys have specific actions;
others can be programmed to perform a desired action, often a shortcut.
Designers are increasingly relying on these function keys to make their
design more efficient for the user.
Examples:
<CTRL>
and C can be programmed to copy highlighted text. F4 can be programmed to
repeat the last operation.
Finally, as well as having different
layout of keys, keyboards also vary in shape and size to offer an
alternative way of reducing risk of repetitive strain injury and/or
increasing speed.
Mouse
The mouse is the most commonly
used pointing device for inputting data and instructions (the keyboard
equivalent being the cursor keys). Objects on the screen are manipulated
by pressing one or more buttons embedded in the mouse and the user moves
the mouse around on a flat surface to generate cursor movement.
The
mouse is highly versatile and is not fixed, unlike the trackball and
joystick which are in fixed sockets. A mouse may be mechanical (with a
small ball) or optical (with optical sensors) which requires a special pad
to help track movements.
Mice are good in small spaces, but a
disadvantage is that drawing with a mouse is very difficult.
Roller Ball
A roller ball is a bit like an upside down mechanical
mouse. The ball is on the surface and the user manipulates the pointer on
the screen by rotating the ball. This device can also be an integral part
of the computer keyboard.
Example:
Laptops often have a
roller ball as part of the keyboard.
Mouse Button
A mouse
button can speed up input as it saves time moving the hand away from the
keyboard. The mouse button is on the keyboard and responds to pressure
applied by the user. The button is in line with the home keys so it can be
easily reached with the index fingers. There are also buttons lower down
that can be pressed with the thumbs for making selections, etc.
Example:
The Toshiba MousePoint® is rapidly gaining popularity
with users because of the time saving factor and also because it does not
require a separate surface.
Speech Recogniser
Speech
recognition as a method of input has potential advantages over other input
devices. It allows the user more freedom because it frees the hands to
perform other tasks. Also people with visual impairments or with severe
motor impairment can gain access to technology which would otherwise be
inaccessible for them.
The main drawback is that speech recognisers
have difficulty distinguishing between similar sounding works and phrases.
If they do get the right words, they then have difficulty interpreting
them. There is also a big problem with interference from background noise
unless a telephone-style handset or a headset are used. For these reasons,
speech recognition is only being used at the moment for very specialised
tasks.
Examples:
Isolated word recognition or recognising
the voice of a single user, simple telephone database enquiries.
Touch Sensitive Screen
A touch screen device produces an input
signal in response to a touch or movement of the finger on the display.
Again, this is a fairly natural form of communication and is easy to use
for people with no computer experience.
Example:
Monopoly
quiz machine in pub - the user is offered a choice of answers to a given
question and points to one of the answers.
Footmouse
Another pointer which works similarly to the mouse is the foot mouse This
is a pedal that pivots with feet movements, moving the cursor on the
screen correspondingly. This input device leaves the hands free for other
tasks.
Automatic Scanner
Automatic scanners are useful
because they require little or no action by the user once the data has
been recorded. The three main types of scanners are:
1. Document
scanner which is useful for inputting large amount of text. It is a high
speed scanner which reads whole pages. It is also useful for diagrams and
pictures.
2. Bar-code reader which is useful for a small amount of
fixed data. The data is stored in a black and white magnetic bar code and
is read in via a gun-like device being passed over or held over the bar
code.
Example:
Supermarket checkouts
3. Optical
character reader which is useful for reading in a variety of hand-written
characters (or marks). A variation of this is magnetic ink character
recognition which reads in characters printed using special ink. This is
more reliable than optical character reader.
Example:
Data
at bottom of cheque.
Marked Card Reader
The marked card
reader is used where there is a limited set of options for input. A
prepared card has the options printed on it and the user marks the card in
the appropriate place to make a selection.
Example:
1. The
National Lottery. Users select 7 numbers on a card which has the first 40
numbers on it. The ink marks made are registered by the computer and the
chosen numbers are printed onto a separate piece of paper.
Eye
Tracking
Like speech recognition, eyetracking allows input where the
user’s hands are occupied or disabled. It works by recording eye
movements in reflected light from the eye. The user must keep a stable
image on the central part of the retina which is not easy, especially if
the targets are very small. Head movement can also be monitored.
Data Glove
A data glove is a wired glove that allows the user
to manipulate objects by apparently grasping objects in 3 dimensional
space. This is currently being researched to discover its possibilities.
As with other gesture devices, there is a transmitting device (i.e. the
glove) and a receiving device (a magnetic field associated with the
computer).
Other Input Devices
Other input devices
include: the graphics table which allows graphics to be input with
movement of the finger across a flat panel; the light pen which emits a
light beam and is used to point at a vertical plane; the pen and notepad
which allows free-hand drawing and writing to be input using a small
electronic notebook; and video which is used where video images are
required.
Visual Output Devices
A major design decision is
which form of output to use in your system. Output can be visual or
non-visual and suitability of each can be affected by the environment of
the user.
Examples:
Screen output may be difficult to view
by a significant portion of users who have visual impairment such as
near-sightedness or colour blindness. There is also bad lighting,
flickering screens and eye fatigue to consider.
Auditory output
may be difficult to hear in a noisy environment or by a user who has a
hearing impairment and auditory data can be much more difficult to
assimilate than visual data.
Example:
Remembering early
items in a spoken menu.
There are a selection of output devices
that can be used to pass output to the user, the most commonly used being
the screen and the printer. It is important that the designer should
select the most appropriate output device for the intended users of the
application and their environment.
Screen
Screen vary in
resolution and price. An expensive, high resolution screen can allow high
quality graphics to be displayed in colour.
Printer
Again,
price can be equated with quality. Inkjet and laser printers give high
quality (sometimes colour) output, but are expensive. Dot matrix and
character printers are cheaper and the quality variable but of a lower
standard.
Plotter
This is a device where different pens
are used to produce coloured output. Suitable for maps and other precision
continuous output.
Microfilm (Microfiche)
Data is stored
on film and magnifiers are required to read the data. This output is more
suitable for long term storage of high volume data.
Video
Video output is in its infancy, but promises to have an impact. In future
an error message may be a video of a person telling you you’ve erred.
Diplomacy on the part of the designers will be required!!
Non-Visual Output Devices
Speech
Speech output devices are very
useful in circumstances where visual output cannot be used effectively.
They also allow visually impaired users to get output and feedback from a
computer which would otherwise be denied.
Example:
A
screen may display an egg timer or a clock to let the user know the system
is doing something. Sound could be used in this instance in the form of
ticking. This would let the user know to wait because something is
happening. Or a voice could say “please wait” (it should be
recognised, however, that badly spoken output is more annoying than badly
designed text output).
As with speech input, speech output is a
more accepted form of communication. It also leaves the users hands free
and allows the user to move away from the terminal and still get the
output. Unfortunately, it requires higher bandwidth and more memory than
corresponding text.
At the moment, the quality of speech output
leaves a lot to be desired, but research continues and improvements are
rapidly taking place.
There are three types of speech output,
concatenation, synthesis-by-rule and recorded speech.
Concatenation
is limited and tends to be used in applications where less than 200 words
are required. It operates by having digitally recorded fragments of speech
which are reassembled into words and sentences and played back.
Examples:
Speaking clock, telephone information such as changed
numbers.
Synthesis-by-rule has the potential for use with
application needing a wide range of vocabulary. It involves having a
database of sounds which are synthesised into words and sentences using
rules of phonemics and rules that relate to the context of a phrase or
sentence. At the moment, the speech output using this type of speech
device can sound very synthetic, despite the fact that the pitch and tone
can be varied. This is the area where improvement is coming through
research.
Recorded speech is the highest quality but, if it requires
large amounts of storage on the computer, it is thus useful for only
limited messages.
Tactile Output
Devices are being used to
provide output using the sense of touch. This is mainly useful for
visually impaired users.
Example:
Braille output
Real-Time Output
In addition to messages and general text,
visual output on a screen may take the form of numerical data, animated
icons and representations of dials, scales and pointers. These latter
methods allow the user to scan the screen and take in information without
having to read any text. There are several factors to consider when
designing real-time output:
Accuracy
The designer has to
consider how accurate the data is required to be and what is an acceptable
error margin.
Example:
The height of an aircraft would be
required to be as accurate as possible whereas the temperature of a
furnace need only be in the correct region.
Change
The
designer should also consider how to display the rate of change and in
which direction the change is happening. Some displays show this with
clarity while others make the interpretation of data very difficult. The
relationship with the real world should also be taken into account.
Example:
When designing a display which represents railway
signals the designer should ensure it relates to the geographical
location.
Visibility
Make sure the information you want to be
noticed can be seen clearly at the distance the user is normally
positioned.
Example:
In some systems text is too small or
the display is so cluttered that important data is not easy to find.
Psychometric Clues
Information from a display is often
contradicted by information from the rest of the body. This can cause
nausea and vertigo.
Example:
Virtual reality and theme
park games.
A major decision is whether or not to display
numerical data in digital or analogue form. These have advantages and
disadvantages:
Interpretation Time
Analogue displays take
longer to interpret than digital.
Example:
On a digital
device, you are given the information immediately rather than having to
decide which number the pointer is pointing to.
Accuracy
It is not always obvious how accurate the information is on an analogue
display. On a digital display, however, the degree of accuracy is clear.
Example:
A digital display may say 3.23745.
Errors
It is easier to make an enormous error with a digital display. With
analogue displays any error is more likely to be quite small.
Example:
Glancing at a hotel’s digital clock when you have jet
lag - you can completely misinterpret the true time. If it’s
analogue, only likely to be out by an hour at most.
Change
It is much easier to see the direction and rate of change on an analogue
display. On a digital changes can be difficult to read - if not
impossible.
Range
On an analogue display the range of the
viewing distance is large compared to that of a digital display.
Scanning
If there are several analogue displays, it is easy for
the user to scan these quickly to look for any irregularities
(particularly when the design is consistent). Scanning digital displays is
much more difficult.
Arithmetic
There is more mental
arithmetic required when using digital displays. With analogue it is much
easier to see differences at a glance.
Example
If you want
to know how long you have before a 2 o’clock appointment, a 1.37
display on your watch will require you to do a small sum to calculate
this.
Resistance
Resistance is any force which slows or
hampers movement. In relation to keys, joysticks, roller balls, etc.,
there must exist a compromise. We don’t want the input device to have
so little resistance that it moves on its own, but we don’t want it
to have so much that it is hard to manipulate. Ideally, we want it to have
the right amount of resistance so that it isn’t tiring to use, but
isn’t moved accidentally at the slightest touch.
Example:
The keys on the keyboard should have enough resistance to allow the users
to rest their fingers on the keys without actually typing anything.
The amount of resistance present is dependent on who the operator
is, where the operator is positioned in relation to the device and the
direction and duration of the movement applied. It is also dependent on
how frequently it is used.
There are different types of
resistance, two of these being frictional and elastic. Frictional
resistance is the resistance encountered when one object rubs against
another.
Example:
The mouse meets frictional resistance
against the mouse mat. However, when you let go of the mouse, it stays in
the position you have put it.
Elastic resistance is the
resistance that forces an object back to its original position after
movement.
Example:
A joystick has elastic resistance. When
you move the stick to a position then let go, it automatically goes back
to the central position.
It should be noted that better quality
QWERTY keyboards have been designed to incorporate negative resistance.
This means the keys are actually more resistant when you first start
pressing them, then they become easier the nearer you are to the
keystroke. This prevents “ghost” typing - you know when you’ve
actually typed something.