There are many different types of control that can be used. The designer should select the control to be included in the HCI to ensure that the user can complete their tasks with ease.

Among the controls that could be used are buttons, form and menus.

Buttons

Buttons can be used to take the user to a specified page or to run a selected action/command. A macro can be run by the user clicking a button. For example a command button can be added to a database user interface to run a search, or to sort or edit data. A button can also display pictures or text.

In HCI terms, a macro is a set of sorted commands that can be replayed by pressing a combination of keys or by clicking a button. A macro enables the user to automate tasks that are performed on a regular basis. This is done by recording a series of commands to be run whenever that task needs to be performed. The complexity of the macro is only limited by the task requirements and the ability of the user.

Once the macro has been recorded, then it can be run by pressing the keys assigned when it was recorded. A macro can also be activated by clicking an assigned button placed on the GUI. A macro will only run when the application program to which it is associated is being used. A macro will not run on its own or with a different application program.

Among the advantages of using macro are:

• a repetitive task can be performed by using a simple action
• errors may be reduced because the instructions included in the macro are run automatically and are the same every time
• inexperienced users can perform complex tasks by using a pre-recorded macro

Among the disadvantages of using a macro are:

• error messages may occur if the conditions when the macro is run are different from those when it was recorded
• users must know and remember the key combination to run the macro
• a macro is pre-programmed so it may not do what the user wants
• if the macro is run from a different starting point than intended, then it may execute incorrectly
• a user can correct errors only if they have some knowledge of how the macro was recorded.

Forms

Forms can be used to assist data entry. A form can give the user help and guidance on what data should be input. Instructions to the user and error messages can be included on forms. It is also possible to include some validation when forms are being used in a system interface. A form may include drop-down boxes for data selection, option boxes and fill-in boxes, which can automatically help a user. Form controls can be used to increase the interactivity with the user and improve usability.

A common example of the use of an automatic fill-in box is when a postcode is entered and the street name and town automatically appear. The user has only to type in the house number. 

Menus

Menus enable a user to select actions. There are several types of menu that can be used, including full-screen, pop-up and drop-down. Each type of menu gives the user available choices of options.

In addition to the considerations mentioned above the designer must ensure that the HCI is easy to learn and use. This will minimise the training requireed and the number of instructions that will need to be learned and rememberedf by the user.

If a user is faced with the error message 'Runtime error at line 89670', then they will probably not know what it means and so they will not know what they should do to rectify the error.

The language used should be helpful and simple, but should not be perceived as condescending by the user. The designer should also be aware of the readability of the language used. Technical language should be kept to a minimum, but should be fit for purpose.

Font styles such as Verdana, Arial and Times New Roman are clearly legible. Other fonts are very difficult to read.

The size of the font used on the HCI is also important and needs to be appropriate to the HCI, to the text in question and to the users. It would be very difficult to use the HCI if the entire font were size 8.

The font style and size of instructions must be clear and consistently used on the HCI and associated screens. Any error messages should also use the same font size and style.

The amount of information available on the screens of the HCI should enable users to effectively use the screen and to complete their tasks. However, a designer must be aware that too much information on the screen can slow the user down because they have to read more information.

Too much information on the HCI can confuse a user when trying to locate the required information. If this happens then the user can begin to lose confidence, the rate of learning will decrease and so the rate at which tasks are completed will diminish.

The layout of the information on the HCI should flow in a logical order. This should be applied to the information given to a user as well as to the information that has to be input by the user.

In addition, any buttons that are used should also be in the same place on each screen of the HCI.

Clearly marked exits should be included in simple and helpful language and they should be in a consistent place on all screens.

The layout should include some white space. This is the amount of empty space on the HCI. Too little white space will mean that the HCI is difficult to read and use, too much white space will make the HCI look bare.

The layout of the HCI should, as far as possible, be consistent with the other applications that are used by the user. Labels and buttons should correspond with the user's idea of what will happen and their previous experience.

Information that is not needed very often should not be displayed, but should be available when requested. For example, a Help icon or menu option should appear on every screen.

Less urgent information should be placed in less prominent positions on the screen in a specific area where the user will know to look when this information is required.

Again, the consistency of the layout will enable users to become familiar with the layout quickly, so increasing confidence and learning.

The colours selected for use in the HCI should not clash, and they should be easily read by the user. Care should be taken to ensure that a user with a sight impediment, such as colour blindness, can also use the HCI.

Colour can also be used to trigger a user's memory. For example, areas where mandatory information should be input could be in a different colour to optional information.

The number of colours used should be limited to four per screen and seven for the whole sequence of screens.

Colours can be used to code information. If this strategy is used, then the designer must make sure the user understands the code and that the colours used match the user's expectations.

Certain colours can be used to draw the user's attention. The most effective colours for this are white, yellow and red.

If displayed information needs to be separated, then colours from different parts of the spectrum should be used. If similar information is shown, then colours which are close neighbours in the spectrum should be used.

It is important to remember that around 9% of the population is colour-blind, with red/green blindness being most common. Colour blind people can discriminate colours using black and white shades, but designers should check that the use of colour is not going to affect the performance of those users.

A designer must consider:

• use of colour
• layout
• quantity of the information on screen
• font size
• complexity of language
• type of controls.