Alphanumericals or alphanumeric characters are any collection of number characters and letters in a certain
language
Language is a structured system of communication that consists of grammar and vocabulary. It is the primary means by which humans convey meaning, both in spoken and signed language, signed forms, and may also be conveyed through writing syste ...
. Sometimes such characters may be mistaken one for the other.
Merriam-Webster
Merriam-Webster, Incorporated is an list of companies of the United States by state, American company that publishes reference work, reference books and is mostly known for Webster's Dictionary, its dictionaries. It is the oldest dictionary pub ...
suggests that the term "alphanumeric" may often additionally refer to other symbols, such as punctuation and mathematical symbols.
In the POSIX/C
locale, there are either 36 (A–Z and 0–9, case insensitive) or 62 (A–Z, a–z and 0–9,
case-sensitive) alphanumeric characters.
Subsets of alphanumeric used in human interfaces
When a string of mixed alphabets and numerals is presented for human interpretation, ambiguities arise. The most obvious is the similarity of the letters I, O and Q to the numbers 1 and 0.
Therefore, depending on the
application, various
subset
In mathematics, a Set (mathematics), set ''A'' is a subset of a set ''B'' if all Element (mathematics), elements of ''A'' are also elements of ''B''; ''B'' is then a superset of ''A''. It is possible for ''A'' and ''B'' to be equal; if they a ...
s of the alphanumeric were adopted to avoid misinterpretation by humans.
In passenger aircraft,
aircraft seat maps and seats were designated by row number followed by column letter. For wide bodied jets, the seats can be 10 across, labeled ABC-DEFG-HJK. The letter I is skipped to avoid mistaking it as row number 1. In
vehicle identification numbers used by motor vehicle manufacturers, the letters I, O and Q are omitted for their similarity to 1 or 0.
Tiny embossed letters are used to label pins on an V.35/M34 electrical connector. The letters I, O, Q, S, and Z were dropped to ease eye strain with 1, 0, 5, 3, and 2. That subset is named the
DEC Alphabet after the company that first used it.
For alphanumerics that are frequently handwritten, in addition to I and O, V is avoided because it looks like U in cursive, and Z for its similarity to 2.
See also
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Alphanumeric brand names
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Alphanumeric shellcode
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Alphanumeric keyboard
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Binary-to-text encoding
A binary-to-text encoding is code, encoding of data (computing), data in plain text. More precisely, it is an encoding of binary data in a sequence of character (computing), printable characters. These encodings are necessary for transmission of ...
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Mathematical Alphanumeric Symbols
Mathematical Alphanumeric Symbols is a Unicode block comprising styled forms of Latin alphabet, Latin and Greek alphabet, Greek letters and decimal numerical digit, digits that enable mathematicians to denote different notions with different l ...
References
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