Alphanumeric characters refer to a set of characters consisting of both letters and numbers. Specifically, the alphanumeric set contains 26 Latin letters, A through Z, and 10 Arabic numbers, 0 through 9. Depending on the specific use, alphanumeric character sets may distinguish between upper- and lower-case letters, meaning the number of alphanumeric characters is either 36 -- if case is not considered -- or 62 -- if it is case-sensitive.

Letters

The Latin alphabet has origins dating back thousands of years
The Latin alphabet has origins dating back thousands of years

The alphabetical component of alphanumeric characters consists of the 26 characters of the modern Latin alphabet. This alphabet is used in written English, French, Spanish, Italian and elsewhere, sometimes with special accents and sometimes without. The alphanumeric alphabet does not contain accented letters and consists of 26 uppercase letters -- A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y and Z -- and 26 lower case letters -- a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y and z.

Numbers

The numerical component of alphanumeric characters consists of the 10 numbers of the modern Arabic numbering system, used throughout the world. The alphanumeric numbers consist of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10.

Historical Origins

Older electronic systems used pulses of electricity to express alphanumeric characters.
Older electronic systems used pulses of electricity to express alphanumeric characters.

The word alphanumeric, whose origins date to 1912, is a combination of the words "alphabetical" and "numerical." The use of a strict alphanumeric set, rather than including punctuation and accents, limited the possible expressible characters. This had widespread applications, ranging from standardizing mechanical printers such as keyboards and ticker-tape printers to formalizing ship naming in the U.S. Navy. A simple alphanumeric base set of characters also meant various language systems could be expected to interface successfully.

Modern Use

Alphanumeric characters appear everywhere.
Alphanumeric characters appear everywhere.

Most people today use an expanded alphanumeric set daily on their computer keyboards. While modern keyboards often include additional punctuation or accent keys, at their simplest, they contain solely alphanumeric characters. Alphanumeric character keyboards are also increasingly found on cellphones and touch-screen computers for text entry. Over the last hundred years, alphanumeric characters have become a mainstay of both written and electronic data entry, with no sign of disappearing anytime soon.