User interface refers to the means by which users interact with a system, including physical, perceptual, and conceptual aspects. There are three main types of user interfaces: natural language, question-and-answer, and graphical user interfaces. When designing user interfaces, guidelines include consistency, providing feedback, permitting easy reversal of actions, and reducing memory load. The goal is to create interfaces that match tasks, improve efficiency and productivity, and are usable and learnable.

2. WHAT IS USER INTERFACE?

3. • The interface (or Human Interface) is the aggregate of means by which
people – the users – interact with the system.
• The user interface is everything the user comes into contact with while
using system – physically, perceptually and conceptually.

4. THREE ASPECTS OF USER INTERFACE:
 The physical aspect- comprise of the devices the user really touches,
including the keyboard, mouse, touch screen or keypad.
 The Perceptual aspects- consist of everything the end user sees, hears,
or touches(beyond the physical devices.
 The conceptual aspects – include everything the user knows about
using the system.this include all the problem domain “things” in the
system the user manipulates, the operation that can be performed and
the procedure followed to carry out operations.

5. TO DESIGN A BETTER USER INTERFACE, USE THE FOLLOWING
OBJECTIVES:
• Match the user interface to the task
• Make the user interface efficient
• Provide appropriate feedback to users
• Generate usable queries.
• Improve productivity of knowledge workers.
The user interface has two main components:
1. Presentation language – the computer-to-human part of the transaction
2. Action language – characterizes the human-to-computer portion

6. GUIDELINES FOR DESIGNING USER INTERFACES
According to Ben Shneiderman, a leading researcher in HCI(Human-computer
Interaction), there are eight general guidelines that are applicable in most
interactive systems. These are the ff.:
1. Strive for consistency – it is imperative to design a consistent-appearing and
functioning interface. The following should be consistent throughout the
system:
a. The way information is arranged on forms
b. The names and arrangement of menu items
c. The size and shape of icons
d. The sequence followed to carry out tasks
2. Enable Frequent Users to use shortcuts. – Users used to work with one
application for the whole day so they quickly loose patience with long menu
sequences and multiple dialog boxes when they know exactly what they
want to do.
3. Offer Informative Feedback – each action taken by the user should result to
some type of feedback from the computer so that the users would know the
action was recognized.

7. 4. Design Dialogs to Yield closure – every dialog should be organized in a
clear sequence with a beginning, middle and end. . Any well-defined
task has a beginning, middle and end; therefore it is the user’s task on
the computer to also feel this way.
5. Offer Simple Error Handling – user errors are costly in both the time
needed to correct them and the resulting mistakes. That is why, if
possible, systems designer should prevent the user from making
errors.
6. Permit Easy Reversal of Actions – users should feel that they can explore
options and take actions that can be canceled or reversed without any
difficulty.
7. Support Internal Locus of Control – Experienced users need to feel that
they are in-charge of the system and that the system responds to their
commands.
8. Reduce Short-Term Memory Load. – People can only remember about
seven chunks only information at a time.

8. TYPES OF USER INTERFACE
The different types of user interface are as follows:
• Natural Language Interface – this permits users to interact with the
computer in their everyday or natural language.
• Question-and-answer Interface - the computer displays a question to
the user on the display. And the computer then takes action on that input
information in a pre-programmed manner, usually by moving to the next
questions.
a dialog box is a type of question-and –answer interface that acts as a
question and answer interface with another application.
• Menu Interface – This type of user interface provides the user with a list
of available selections on the computer screen.

9. • Form-Fill Interface – also referred to as input/output forms, this
interface consists of onscreen forms or web-based forms that display
fields containing data items or parameters that need to be
communicated to the user
• Example of form fill interface of facebook

10. • Command – Language Interface – this user interface allows the user to
enter explicit statements to invoke operations within the system.
Example :
COPY C:NAMES.DOC A:NAMES.DOC
• Graphical User Interface – this types of user interface allows users to
directly manipulate the graphical representation on the screen, which
can be done with keyboard input, a joystick or a mouse.
• Other user interface include pointing devices:
• Stylus – a pointed stick that looks like a pen.
• Touch-sensitive screens – allow users to use finger in activating the display
• Voice recognition and synthesis – allows the users speak to the computer
while the system is able to recognize the individuals vocal signals, convert
them and store input

11. TWO MAIN DEVELOPMENTS IN SPEECH RECOGNITION ARE:
1. Continuous speech systems that allow for the input of regular text in
word processors
2. Speaker independence so that any number of people can enter
commands or words at a given workstation.
Some standards to consider in assessing the interfaces you have chosen
are follows:
1. The training period necessary for users should be acceptably short.
2. Users who are early in their training should be able to enter commands
without thinking about them or without referring to a help menu or
manual.
3. The interface should be faultless so that errors are few and those that
do occur are not occurring because of poor design.
4. The time that users and the system need to recover rom errors should
be short.
5. Occasional users should be able to study again the system quickly.

12. GUIDELINES FOR DESIGNING DIALOG
Dialog is the sequence in which information is displayed to an obtained
from a user. A well-designed dialog makes it easier for users to use a
computer and it leads to less frustration with the computer system.
There are three main points for designing good dialog and these are
follows:
1. Meaningful communication so that the computer understands what
people are entering and people understand what the computer is
presenting or requesting.
2. Minimal user action
3. Standard operation and consistency