Section 1.3
Introduction To Computing
1.3 The Human-Computer Interface
The term 'Human-Computer Interface' (HCI) describes the interaction between the
user and the computer.
All computers require some sort of HCI.
The following are a list of tasks for which special purpose interfaces are
required:
- getting cash from an ATM
- a jest pilot checking an instrument panel
- a modern photocopier
1.3.1 Interface Design Principals
When designing an interface, we wish to ensure that users perform tasks:
- Safely
- Effectively
- Efficiently
and possibly:
The Considerations
- Who will use the system?
- What tasks is the computer performing?
- What environment will the computer be used in?
- What is technologically feasible?
1.3.2 Command Driven Interfaces
In order to instruct the computer, the user has to type in the command and enter
it to be processed.
Advantages
- Could be quicker to enter more complex commands that would normally
have to be accessed via a number of menus.
Disadvantages
- The user must learn and use the command syntax.
- Little or no help support. Vague error messages.
1.3.3 The WIMP Environment
WIMP stands for Windows, Icons, Menus, Pointers
Windows
Can be used to display software or files. Easy to manipulate. Often allow more
than one task to be viewed at once.
Icons
Represent a file or directory or a frequently accessed task.
Menus
Menus allow much of the complexity of the software to be hidden until needed.
Pointer
Controlled by mouse - used instead of keyboard.
Full Screen/Window Menu
This type of menu reamins on screen until the user makes a choice. Usually used
at the start of an application.
Pull Down Menus
Pull down menus are usually displayed at the top an application menu. When the
user clicks on an item a menu appears.
Pop Menus
Usually pop-up in response to an action referring to a particular object.
When a user is required to enter data it is common to display a form on the
screen for a user to fill in.
In a WIMP environment forms are usually called dialogue boxes.
Forms should have:
- a title
- plenty of space
- an indication of how many characters should be present in each
field
- default values where possible
- a facility to allow the user to go back and correct mistakes
- items displayed in a logical sequence
- exit and help facilities
- written messages mainly in lower case
- a sensible number of 'attention grabbing' devices
Speech/Sound Output
Whole messages or individual words are spoken and recorded digitally. Output
that would normally be displayed can be 'spoken' by the computer.
Uses
- Phone banking
- '192' Directory enquires
- Document text speakers
Command And Control Systems
Such systems recognise a small vocabulary of technical terms.
Uses (In PCs):
- Run software
- Control printing
Uses (In Business):
Large Vocabulary Dictation Systems
With these systems the computer is controlled by instructions spoken in whole
sentences.
If the system is unsure what a particular word was it can examine the structure
of the sentence to predict what the word was.
Natural Language Dialogue Systems
These types of interfaces allow the user to instruct the computer without need
for a particular 'syntax'.
Advantages:
- It is a form communication that is natural to people requiring little
or no training.
- There is no 'syntax' to follow - the computer will adapt to different
ways of speaking.
However:
- The computer may not recognise some extreme accents.
- Artificial languages may be more concise.
- Although there is some controversy on this point, some people believe
that after a while people may become to regard the computer as human.
