The Principles of Good Form Design

When you design a form, you should maintain as much consistency as possible. Keep the following design concepts and tips in mind:

• Consistency of forms. Make all the forms in a multiform application consistent with each other. A good form should display the same information in the same way, all the time. Therefore, don't call a data item Vendor No. on one form or control and then call the item Vendor Num elsewhere. This makes the form and application more difficult to understand. If the same information is displayed differently on different forms, it should be for a good reason-not because it looks better. Also, don't change labels on the same command buttons. If one form's command button caption is Cancel, don't change the caption to Quit on another form's command button.
• Consistency of standards. Use the same standards throughout the application. Name controls, procedures, variables, and other objects consistently. Prefix variables to help identify their data types, or use data-type suffix characters.
• Consistency of button location. When possible, locate similar command buttons in the same positions on all forms. Don't, for example, place an Exit command button in the center of one form and in the lower-right corner of another form.
• Consistency of color. Use color to make important information stand out. Set foreground and background colors so that they blend well; don't use clashing colors or try to impress. For the best results, stick to the standard Windows colors used in major applications such as Microsoft Word. (You could add a surprise color for warning purposes, such as a negative balance in a checkbook program.)
• Consistency of readability. Make the form easy to read. Don't use all uppercase letters for titles or other labels except in rare cases. Keep lots of white space (the blank areas on a form) on the form for clarity. Use a different font for labels and for text boxes that the labels describe, unless the controls' border style and background properties help distinguish them already. Don't mix too many fonts on the same form, however.
• Consistency of clarity. Don't clutter the form with too much information. Express but don't try to impress. Although the VBScheduler application form shown in Figure 33.1 is simple, the form is perfect for the application and gives users all available information without too much clutter. VBScheduler requires only a single form, but if the form gets too crowded, using a second form is smarter than squeezing too many more controls on one.
• Consistency of simplicity. Make data entry simple. Use a drop-down list box when users need to select from a limited number of choices. Analyze the focus order so that pressing the Tab key sends the focus to the next control in line to receive the focus. Add hot keys to text-box labels so that users can move directly to the text box. Never let users answer Yes or No questions by typing Yes or No, but supply check boxes, option buttons, and command buttons for such controls. The simpler you make data entry, the fewer user errors will occur.