A specific encoding of letters, numbers and punctuation into dots and dashes devised by Samuel Morse. Common letters are encoded into short sequences so it's fairly efficient. In fact, this form of encoding is the general basis (short codes for frequent symbols) of several CompressionAlgorithm''''''s.

How well did Morse do? Here is the code listed in the order of letter frequency for English language press reporting (early application of the telegraph). I've represented dots as . and dashes as ... which is their normal 1:3 duration ratio. Other than a poor choice for o, he got it pretty right.

 e .
 t ...
 a . ...
 o ... ... ...
 n ... .
 i . .
 s . . .
 r . ... .
 h . . . .
 l . ... . .
 d ... . .
 c ... . ... .
 m ... ...
 u . . ...
 f . . ... .
 p . ... ... .
 g ... ... .
 w . ... ...
 y ... . ... ...
 b ... . . .
 v . . . ...
 k ... . ...
 j . ... ... ...
 x ... . . ...
 q ... ... . ...
 z ... ... . .

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For a recently written history of Samuel Morse, his invention and the revolution that was the telegraph era, see ''The Victorian Internet'' ISBN: 0425171698.
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As of Dec 2006, the FCC has dropped the requirement for amateur radio operators in the United States to be able to do MorseCode at 5wpm to be licensed.
See also IambicPaddles http://c2.com/morse