User Interfaces

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 :

  1. Whether the program will do the jobs you want it to.
  2. 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 :

Types of User Interface

There are three different types of user interface :

  1. The Command Line Interface
  2. The Menu Driven Interface
  3. The Graphical User Interface (GUI)

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 operating system have a graphical user interface.

The Command Line Interface

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 :

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 :

  1. MS-DOS
  2. BBC Micro
  3. Quest database
  • 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.

The Menu-Driven Interface

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 :

  1. Wordwise word processor

  2. A bank cash point machine

  3. Grass database

  • 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.

The Graphical User Interface

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/programs that have a WIMP Interface are :

  1. Windows
  2. Risc-Os
  3. 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.

  • Most operations are self-explanatory so that you do not have to remember lots of commands.
  • 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.

Important Aspects of a User Interface

There are many things that we need to consider to decide if a user interface is suitable for a task. These include :

  1. What type (Command, Menu, GUI) of interface is it ?
  2. How easy is it to use for novice users ?
  3. How easy is it to use for experienced users ?
  4. Can actions be carried out quickly ?
  5. How easy to understand are error messages ?
  6. What help facilities are provided ?
  7. Is there a tutorial ?
  8. Do many programs use the same user interface ?
  9. Does the interface run fast enough on my computer ?
  10. How much memory does the interface use ?

Designing a User Interface

When you are designing an information system you will need to design the user interface. It is likely that because you are using an application 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. Remember to bear in mind the guidelines (e.g. using simple language) given at the top of the page to help you.

Special Purpose User Interfaces

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 :

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.


(1)What tools and techniques do software designers use to make a user interface easy to operate ?
(2)What are the three types of user interface ?
(3)Describe a method of interacting with a computer that does not involve the use of menus.
(4)What do the acronyms GUI, WIMP and WYSIWYG stand for ?
(5)Name three input devices that could be used to move a pointer around the screen with a GUI.
(6)Why is it important to use a warning buzzer in an aeroplane cockpit ?

(C) P. Meakin 1998