User Interfaces

1. Introduction

A user interface is the method by which a human and a computer system exchange information and instructions.

You may like some programs and dislike others. When you decide whether or not a program is useful you will probably be considering :

Whether the program will do the jobs you want it to.
How easy it is to use the program.

It is the job of a user interface to make a program easy to use. Today the user interface is regarded as being so important that up to 90% of a computer program may be devoted to managing it. Software designers use many tools and techniques to help make an interface easy to use. These include :

Colour to highlight.
Sound for warning messages.
Flashing symbols.
Careful design of screen layouts.
Keeping the interface consistent on all of the screens of the program.
Using simple language.
Choosing appropriate input devices. e.g. mouse, keyboard, bar code scanner.

User interfaces are usually classified as being one of three different types : Command Line, Menu Driven or Graphical User Interface (GUI).

2. Types

There are three different types of user interface that are in common use. They are :

Types of User Interface
Command Line	The user interacts with the computer by typing commands.
Menu Driven	The user interacts with the computer by selecting options from a menu.
Graphical User Interface (GUI)	The user interacts with the computer by using a pointing device such as a mouse or trackball.

Each type of interface has its own advantages and disadvantages. Often the type of user interface that is used on a computer system is determined by the operating system. For example most programs that run on computers using a Microsoft Windows® XP operating system have a graphical user interface. Another type of user interface that is less commonly used is speech driven.

Windows® XP is a registered trademark of Microsoft Corporation in the United States and other countries.

3. Command Line

With a command line interface the user interacts with the computer by typing commands .

An interaction with a computer using a command line interface usually follows these two steps :

The user types a command e.g. "dir".
The computer carries out the command and displays its results.

Here is an example conversation in MS-DOS®. The user first asks the computer to go to the directory "c:\apps\dtp". He then instructs it to start the program "word".

Examples of systems which use a command line interface are :

MS-DOS®
BBC Micro
Quest database

Advantages	Disadvantages
An experienced user who knows a package well can enter commands quicker than he could select options using lots of menus. Can be used on a computer which has very little memory and is slow.	It is very difficult to remember all the possible commands and exactly how they should be typed. Error messages are not usually very helpful.

Very few new computer programs are developed to use a command line interface.

MS-DOS® is a registered trademark of Microsoft Corporation in the United States and other countries.

4. Menu Driven

With a menu driven interface the user interacts with the computer by selecting options from a menu.

A typical program will have many menus which the user can access. Here is an example of one menu from a word processing package :

Menus can be either full screen or pull-down. Pull-down menus are accessed by selecting the menu from a menu bar. Pop-up menus are activated by pressing a button on the mouse.

Examples of systems which use a menu driven interface are :

A bank automatic teller (cash) machine.
A handheld electronic organiser.

Advantages	Disadvantages
The user does not need to remember and type lots of commands. Because menus contain explanations of the options that are available you can guess how to use a program without having to refer to a user guide	You may have to switch screens to access a menu.

5. Graphical User Interface (GUI)

With a Graphical User Interface (GUI) the user interacts with the computer by using a pointing device such as a mouse or trackball.

The most popular form of GUI is a Windows, Icon, Menu and Pointer (WIMP) system. The important features of a WIMP system are :

1.	Window : An area of the screen which is used to display a particular program or piece of work. Many windows can be displayed on the screen at the same time. e.g.

2.	Icon : An informative picture / symbol displayed on the screen which the user chooses to select an action. Icons can usually be used to represent software packages, documents and hardware devices. e.g.

3.	Menu : A list of options which the user can pick from. Menus can be pull-down (selected from a menu bar at the top of the screen) or pop-up (selected by pressing a mouse button). e.g.

4.	Pointer : A symbol such as an arrow which is moved by a pointing device and can be used to select objects.

WIMP user interfaces are now very popular and are used on most computers. Examples of operating systems and programs that have a WIMP Interface are :

Windows® XP
Risc-OS®
Any piece of software running under one of the above operating systems.

When you use a program such as a word processor that has a WIMP interface it is often the case that the document you are creating looks exactly the same on the screen as it will when it is printed out. If this is the case then the program is described as being WYSIWYG. This stands for What You See Is What You Get.

Advantages

Disadvantages

Most operations are self-explanatory so that you do not have to remember lots of commands. This makes GUIs particularly suitable for inexperienced users.
Some operations are much easier using a GUI with a pointer. e.g. selecting text or drawing pictures.
Often you can have more than one program running at the same time, each of them using different windows.
Often GUIs are WYSIWYG. What you see on the screen is what you get if you do a printout.
Often with a GUI many programs use a similar interface, so it is easier to learn how to use a new program.
Most GUIs provide good help facilities.

GUIs can take up a lot of memory and need to be run on a fast computer. If you have a slow computer, a GUI may work slowly or not at all.

MS-DOS® and Windows® XP are registered trademarks of Microsoft Corporation in the United States and other countries.

6. Speech Driven

A speech driven user interface is controlled by a user speaking commands. Speech driven interfaces are not very common at the moment but may become more popular in the future. Commands can be input using a microphone and are interpreted by voice recognition software. Output can be provided either on a monitor or by speech synthesis.

Speech driven user interfaces have a number of advantages over more traditional methods such as command line or graphical user interfaces :

Very little training is required, all a user has to do is learn what commands can be used.
You can use a speech driven interface when you need to use your hands or eyes for something else.
There is no risk of repetitive strain injury when you use a speech driven interface.

A speech driven interface may need to be trained to recognise the voice of the user. This is particularly likely with systems that understand a wide range of commands. It may be difficult to use a speech driven interface if there is a lot of background noise or if you have a cold that makes your speech unclear.

Speech driven interfaces are often used by in-car mobile telephones. So that a driver does not need to take his eyes off the road or his hands off the steering wheel he is able to control the telephone by speaking commands such as "Dial Emma" or "Hang Up". In the future it is likely that they will be used in devices such as televisions as an alternative to a remote control.

7. Designing

When you are designing an information system you will need to design the user interface. As you will probably be customising a generic package you will have to design your interface to fit in with the facilities the package offers you.

You should try sketching the layout of the screens that you will include in your system before you set the system up. These guidelines will help you develop an appropriate user interface :

Positioning	Position items in a logical order on the screen. Usually the user will read the screen from the top down and from left to right, so information should be positioned in this order. Related pieces of information (e.g. surname, forenames) should be grouped together.
Consistency	Make each screen that the system displays similar to the others. e.g. always use the same colour background, the same style of writing for prompts, always put the titles and any icons in the same place on the screens.
Cluttering	Do not clutter the screen by putting too much information on it.
Colour	Use colour to highlight - red is often used for warnings. Flashing symbols can attract a user's attention.
Sound	Sound can be used to alert users to urgent events such as an error occurring.
Help	Include appropriate help information with the system so that the user can discover how to use the system and overcome any problems he encounters.
Language	Use simple language. This is particularly important if the system is aimed at young people.
Input Devices	Choose appropriate input devices. e.g. mouse, keyboard, bar code scanner.

8. Assessing

If you are asked to evaluate or select a software package then you will need to look at what functions the package can carry out and the quality of the user interface.

Here is a list of some points you could consider when evaluating a user interface :

What type (Command, Menu, GUI) of interface is it ?
How easy is it to use for novice users ?
How easy is it to use for experienced users ?
Can actions be carried out quickly ?
How easy to understand are error messages ?
What help facilities are provided ?
Is there a tutorial ?
Do many other programs use a similar user interface ?
What are the minimum and recommended hardware requirements to use the interface ?

9. Special Purpose

For some applications a special purpose user interface is required. These are applications for which a standard user interface on an ordinary computer is not suitable. Here are two applications for which this is the case :

Flying an Aircraft

Pilots use computers to fly aeroplanes. But a pilot does not fly an aeroplane using a mouse and a monitor. The pilot would not be able to control the plane quickly enough to prevent a crash with a mouse and there is not enough space on a monitor to give the pilot all the information he needs. Instead specialised input devices such as a yolk, pedals and many banks of switches and levers are input devices. Output devices such as computer monitors, dials and warning buzzers are used to pass information to the pilot.

Automatic Teller Machine (ATM)

People who use a cash machine (ATM) do not want to have to learn how to use a computer to get money. So a very simple menu driven interface which uses a small keypad and card slot as input devices is employed. Output is provided by a monitor, a small printer and the hole that the money comes out of.

A special purpose user interface consists of not only software but also all of the input devices and output devices used to enable communication between the user and the computer.

GCSE ICT Companion 04 - (C) P Meakin 2004