Seven-segment Display - Displaying Letters

Displaying Letters

Hexadecimal digits can be displayed on seven-segment displays. A particular combination of uppercase and lowercase letters are used for A–F; this is done to obtain a unique, unambiguous shape for each letter (otherwise, a capital D would look identical to an 0 and a capital B would look identical to an 8). Also the digit 6 must be displayed with the top bar lit to avoid ambiguity with the letter b)

In addition, seven segment displays can be used to show various other letters of the latin, Cyrillic and Greek alphabets including punctuation, but few representations are unambiguous and intuitive at the same time. Short messages giving status information (e.g. "no disc" on a CD player) are also commonly represented on 7-segment displays. In the case of such messages it is not necessary for every letter to be unambiguous, merely for the words as a whole to be readable.

Similar displays with fourteen or sixteen segments are available allowing less-ambiguous representations of the alphabet.

Using a restricted range of letters that look like (upside-down) digits, seven-segment displays are commonly used by school children to form words and phrases using a technique known as "calculator spelling".