The human/computer interface (or man/machine interface) is a term used to describe the interaction between a user and a computer. In other words the method by which the user tells the computer what to do, and the responses which the computer makes.

Do not allow the word computer limit your vision to a PC sitting on an office desktop. You also need to think in terms of cash machines, aeroplane instrument panels, photocopiers, etc.

Allows users to carry out their tasks: -

• Safely - (In the case of a pilot for example)

• Effectively - (Does the job it's supposed to do)

• Efficiently - (Does not waste time, or make life difficult for the user)

• Enjoyably - (Makes learning fun?)

Well-designed systems can improve the output of employees, improve the quality of life and make the world a safer and more enjoyable place to live in.

In order to design a usable interface the designer must consider: -

WIMP stands for Windows, Icons, Menus and Pointers.

A window is a box on the screen that contains some data or application that the user can view. They can be maximised, minimised or restored. They can also be arranged on top of one another or tiled. Next time you use MS Word open 2 documents and go explore the Windows menu.

An icon is a picture that represents an application, data file or folder. Clicking on the icon activates a link to the relevant file.

Menus come in several different formats:

Forms are often used when the application requires input in a specified format. For example when the user must enter personal details on a web site. It is important that the form is designed in a way that makes it as user friendly as possible. The following design points should be noted:

• The form should have a title to identify it.
• The form should not be too cluttered. Spaces and blanks in a display are important.
• It should give some indication of how many characters can be entered in each field of data.
• The user should be given a chance to go back and correct any field before the data is accepted.
• Items should appear in a logical sequence to assist the user.
• Default values should be pre-written onto the form so that a minimum of data entry is required.
• Full exit and 'help' facilities should be provided.
• Lower case in a display is neater and easier to read than upper-case.
• 'Attention-getting' devices such as blinking cursors, high-intensity, reverse video, underlining etc should not be over-used.

Dialogue boxes are a special type of form often associated with the Windows environment; an example shown below is the 'Save as..' dialog box from Internet Explorer.

A Wizard is an interactive help utility that guides the user through a complex task, such as creating a query in MS Access. Wizards are often set up as a series of dialog boxes through which the user can move backwards and forwards, entering the required data and parameters.

With this type of interface very little help is given to the user, who has to type a command such as, for example, DELETE FILE1 to delete a file. Commands enable a user to quickly and concisely instruct the computer what to do, but they do require the user to have knowledge of the commands available and the syntax for using them. How for example do you delete two files?

Q1: Identify TWO situations in which a command-driven interface would be appropriate.

The ultimate in user-friendly interfaces would probably be one in which you could simply tell your computer what to do in ordinary speech. Two distinct types of voice recognition system are emerging; small vocabulary command and control systems and large vocabulary dictation systems.

• Command and control systems (like those on mobile phones) can be relatively small and cheap because they need only a small, tightly defined vocabulary of technical terms.

• Large vocabulary dictation systems can handle whole sentences and extensive vocabularies but need much greater processing power and memory space. These systems use elaborate probability distributions to estimate which word the acoustic pattern it has picked up is most likely to be, partly by looking at other words in the developing sentence and predicting what sort of word (noun or verb, for example) is likely to be used.

• Most natural form of dialogue for humans — no need for training in a specialised command language.
• Extremely flexible and powerful.
• The user is free to construct his own commands, frame his own questions, etc.

Speech/sound output

A speech synthesis system works as follows:

Individual words and sounds are spoken into a microphone by a human being and recorded by the system, thereby training it to speak. Output that would normally be printed can then be spoken, so long as the word is contained in its vocabulary. Sometimes words that are not recognised are spelt out.

Such a system has limited use but could for example be used by a bank computer connected by telephone line to customers' homes and offices. The customer could key in his account number using the telephone keypad, and the computer could then access his account and speak out the customer's account balance.

Sometimes the HCI is provided by special hardware and software, for example in a cash dispensing machine, or in an automatic pilot system in an aircraft where special dials convey information to the human pilot. Embedded computers are computers built into special purpose equipment and controlled by an interface specific to that purpose, like a washing machine.