Cryptography has always fascinated me ever since I read The Dancing Men in Sir Arthur Conan Doyle's the Adventure of Sherlock Holmes. Above I attached the images from the original book. The criminal and our heroine communicated secretively with each through a system of symbolic language using the dancing men in substitute of alphabets. Holmes deciphered it in the same way Edgar Allan Poe explained cryptogram, which is quoted in page 217 in Gleick's book.
Now let's have a look at those messages. Sherlock Holmes realized, in the story, that the most frequent image appearing would be the letter E, and that the name of the heroine Elsie will be int he message somewhere. With that information, he managed to decipher the code.
Message one: Am here, Abe Slaney
Message two: At Elrig Es.
Message three: Elsie, prepare to meet thy god
As we can see, language became a medium of information and only those who understand the system: vocabulary, grammar, etc, can use it to convey information and messages. Without the understanding, language is just another cryptography. On the other hand, when we understand the system of the cryptography, it became another set of language with structure and regularity, and can be used as a medium of information...just like what Abe Slaney and Elsie Patrick did in the story of the Dancing Men.
Alan Turing's machine serves to decipher cryptograms, and is the founding father of computer science and artificial intelligence. Gleick illustrated, reiterated and demonstrated through the book about this subject, that is, to use another information system in order to ease up the conveying of the message in adaptation of the medium. The way we program our computers or robots is just like that: we put in the information so that the machine understand the "mechanic language", through the programed system, the output would be understandable to human.