Calculator spelling

An unintended characteristic of the seven-segment display is that many numbers, when read upside-down, resemble letters of the Latin alphabet. Each digit can be mapped to one or more letters, creating a limited but functional subset of the alphabet.

The graphic below illustrates with the sequence "250714638" appearing inverted as "BEghILOSZ":

Certain calculators omit the topmost stem on the digit "6" and the bottom-most stem on the "9". In such cases, "6" renders a lowercase "q" when turned upside-down, and "9" appears as a lowercase "b".

Other variants of calculator spelling alphabets consider "0" to be a capital "D" instead of "O", "6" (not used in the standard Beghilos) as a lowercase "g" (as opposed to uppercase represented by 9) and "9" as either a reversed lowercase "a" or an at sign (@), both of which represent the letter A.

Extending the available alphabet to hexadecimal notation (generally available on lower-end scientific calculators, though not on basic models), "b" and "d" correspond to "q" and "p" respectively. "F" transforms to a mixture between a "J" and a "t". A and C do not transform readily to recognizable letters. E transforms to 3. C transforms to an open O. Upside-down A is the # sign.

Using leet, additional letters can be represented by combinations of letters (11/II or 2 ["Z" being very rare in English] representing "two" or "to", 111/III representing "three", 15/SI, 935/SEa or 335/SEE for "C", etc.). This is generally rare and, especially in the last case (using a spelling-out of a letter) severely limits readability.

Only certain calculators are capable of being used for beghilos calculator spelling. LCD, VFD, LED, and Panaplex displays are best for spelling words. The ability of dot-matrix displays, fourteen-segment and sixteen-segment displays to render most characters defeats the purpose of spelling with a limited alphabet.

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Wikipedia