Direct Manipulation

• Video games (joy sticks, steering wheels, toy ray guns)
• CAD (Computer-aided design)
• Desktop GUI, WIMP Interface (Windows Icons Menus Pulldowns)

The trick in creating a direct-manipulation system is to come up with an appropriate representation or model of reality. A metaphor. Personal computer systems often use the "desktop metaphor" where icons of familiar office or desk top items are displayed on screen... calendars, in-boxes, and of course folders and documents.

Command-line interface users (VAX, Unix, and DOS) may use words like "directory" and "file" but GUI users (Mac and Windows) use words like "folder" and "document" to mean the same thing.

An airline reservation system with a direct manipulation interface might present a map to prompt for cursor motion to indicate the starting and destination cities, and a calendar and clock to prompt for departure and arrival times.

Quicken displays a checkbook register with labeled columns for check number, date, payee, and amount. Check marks can be made to indicate verification against the monthly bank statement.

Potential Problems with Direct Manipulation

Spatial or visual representations may be too spread out, take up too much room. There might not be enough screen real-estate, not enough glass, for all the information to be seen at once. Thus, the need for off-page connections or window scrolling or multiple actions.

A second problem is that the user must learn the meaning of the visual components. A graphic icon may have had meaning to the designer, but require learning time for the user.

For example, in Word 97 it is fairly obvious that the little scissors icon on the toolbar means "Cut." But, there are other icons on the toolbar that may not seem quite so intuitive. Fortunately, in Word, if you point at an icon on the toolbar text pops up to tell you what that button does.

First-time Macintosh users were often confused about one element of its otherwise very intuitive graphic interface. The Mac OS would delete a file if you drag its icon to the Trash can icon. (In Windows this concept is called the Recycle Bin.) Unlike your Intel-based PC the floppy disk drive on a Macintosh has no eject button. If you wanted to eject your floppy disk you would drag its icon to the very same Trash can. This confused new Mac users who would worry that dragging a floppy's icon to the Trash will erase the floppy. (It won't.)

Yet another problem with a GUI interface is that for experienced typists, taking one's hand off the keyboard to move the mouse may be slower than typing the relevant command.