User Performance and Preference for Alphabetic Entry from 10-Key Pads: Where to Put Q and Z?

Abstract

The numeric keys on the keypads of devices such as telephones and point of sale terminals have the letters of the alphabet mapped onto the digits 2-9, except for Q and Z, which are missing. The international standards bodies CCITT and ISO/TEC are standardizing the placement of letters on 10-digit keypads, and must decide where to place Q and Z. Two alternatives have been considered: placing Q and Z in alphabetic order on the 7 and 9 keys, respectively, or placing Q and Z on the 1 key. A study was conducted to determine if one of these alternatives is to be preferred on the basis of human keying performance and/or preferences. Performance differences were too small to conclude that one alternative should be preferred, however, the majority of users clearly indicated a preference for alphabetic order. A nation-wide preference and usage survey among active calling card and bank machine users revealed an overwhelming preference for the alphabetic order. Finally, a summary is given of the current status of the 10-key pad standardization process in CCLTT and ISO/TEC.