Reasons for Design Choices

The primary reason for choosing a hybrid menu and question/answer interface for the TURBOMail system was to adhere to the design philosophy of providing a simple interface for the user. The decision was made to eliminate the keyboard as an input device to avoid user confusion, since keyboard usage may be ambiguous (the user may not know whether to type in a single key, or a key sequence, to activate a function; many keys will be extraneous to a function at a given time, etc.). This decision eliminated the use of a forms-based interface from consideration, since the primary entry of forms data would be by keyboard.

The decision to favor a button interface over a pointer interface to the menu and question/answer interface was to avoid the problems associated with positioning and operating a pointer on screen. Pushing a button is a direct manipulation of the environment, as opposed to pushing a virtual button which is abstracted an additional level from the user's manipulation (the touchscreen, which is a variant of the virtual button, was also disregarded for this reason). This also mirrors the current interfaces in ATM devices, on which the TURBOMail system was based. A button interface may also be clearly marked in Braille for blind users, thereby providing access for those users as defined in the section on user identification.

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