Codes and ciphers have been used since ancient times. The word CRYPTOGRAPHY, meaning the science of codes, comes from the Greek words kryptos (secret) and graphos (writing).
    In 405 BC the Greek general LYSANDER OF SPARTA was sent a coded message written on the inside of a servant's belt. When Lysander wound the belt around a wooden baton the message was revealed. The message warned Lysander that Persia was about to go to war against him. He immediately set sail and defeated the Persians. The Greeks also invented a code which changed letters into numbers. A is written as 11, B is 12, and so on. So WAR would read 52 11 42. A form of this code was still being used two thousand years later during the First World War.
    The Roman ruler Julius Caesar (100 B.C. - 44 B.C.) used a very simple cipher for secret communication. He substituted each letter of the alphabet with a letter three positions further along, so that A became D, B became E and so on. His famous phrase VENI, VIDI, VICI ("I came, I saw, I conquered") would have read YHQL YLGL YLFL Later, any cipher that used this "displacement" concept for the creation of a cipher alphabet, was referred to as a Caesar cipher. Of all the substitution type ciphers, this Caesar cipher is the simplest to solve, since there are only 25 possible combinations. Often this type of cipher is implemented on a wheel device. A disk or wheel has the alphabet printed on it and then a movable smaller disk or wheel with the same alphabet printed on it is mounted forming an inner wheel. The inner wheel then can be rotated so that any letter on one wheel can be aligned with any letter on the other wheel.
For example, if the inner wheel is rotated so that the letter M is placed under the letter A on the outer wheel, the Caesar cipher will have a displacement of 12. To encipher the letter P, locate it on the outer wheel and then write down the corresponding letter from the inner wheel, which in this case is B. The same can be accomplished by placing alphabets on two pieces of paper and sliding them back and forth to create a displacement.
After the fall of the Roman Empire codes were not used much until the sixteenth century. Then Italian and French scholars began to make up very complicated codes. The science of code-breaking - CRYPTANALYSIS - had begun In Elizabethan England MARY QUEEN OF SCOTS sent coded messages to her supporters who where plotting to murder Queen Elizabeth I.  The messages were intercepted by the head of Elizabeth's secret service, Sir Francis Walsingham. He deciphered them and discovered the plot. Mary was executed for treason in 1587.
     Modern Codes:
Morse Code and Telegraphy:
The invention of MORSE CODE in 1838 by the American, Samuel Morse, created an entirely new way of sending messages quickly over long distances. Morse is not actually a code but an ELECTRO-MAGNETIC TELEGRAPH SYSTEM which used signals of 'dots' and 'dashes' to represent letters of the alphabet. If a message in Morse was to be kept secret, it had to be put into code before it was sent.
Look at the Morse alphabet on the left. See how each letter is shown in dots and dashes. Morse code was sent using a TAPPER.

Letter Morse   Letter Morse   Digit Morse
A .-   N -.   0 -----
B -...   O ---   1 .----
C -.-.   P .--.   2 ..---
D -..   Q --.-   3 ...--
E .   R .-.   4 ....-
F ..-.   S ...   5 .....
G --.   T -   6 -....
H ....   U ..-   7 --...
I ..   V ...-   8 ---..
J .---   W .--   9 ----.
K -.-   X -..-
L .-..   Y -.--
M --   Z --..

Letter Morse   Punctuation Mark Morse
? .-.-   Full-stop (period) .-.-.-
? .--.-   Comma --..--
? .--.-   Colon ---...
Ch ----   Question mark (query) ..--..
? ..-..   Apostrophe .----.
? --.--   Hyphen -....-
? ---.   Fraction bar -..-. 
? ..--   Brackets (parentheses) -.--.-
  Quotation marks .-..-.
By the end of the First World War, armies and navies sent many of their important orders by telegraph or wireless using Morse. British and German code-breakers tried to intercept and decode each other's messages. TELEGRAPHY is a method of sending messages by electrical impulses through a wire. To work it needs: Morse code and telephones are examples of telegraphy in action.

WIRELESS transmission means that messages are sent by RADIO WAVES through the air. To work in both directions it needs:

Both these methods of communication were used during the First and Second World Wars. The Second World War made famous another code - Enigma. But this is another story.

Some other famous cyphers:
-The Vigenere Cipher
-The Gronsfeld Cipher
-Simple Substitution Cipher