Reasons to question seven segment displays.

Seven segment number displays are ubiquitous and popular. They are simple and familiar. They seem to make economic sense, and with only seven segments they require little wiring and electronics to support. They are cheap to buy and cheap to use; they make seemingly effective and unproblematic products. This paper illustrates many examples of problematic uses of seven segment displays that could have been avoided. More generally, the paper raises design questions and some solutions to be considered when designing numerical displays, and certainly before uncritically using seven segment displays. Although there are markets and applications where cost may be an overriding consideration, for safety critical and other dependable types of use (including general purpose devices that may sometimes be used for critical tasks) more legible alternatives than standard seven segment displays should be preferred.