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Codes can be used for brevity.

When telegraph messages were the state of the art in rapid long distance communication, elaborate systems of commercial codes that encoded complete phrases into single words ( commonly five-letter groups ) were developed, so that telegraphers became conversant with such " words " as BYOXO (" Are you trying to weasel out of our deal?

"), LIOUY (" Why do you not answer my question?

"), BMULD (" You're a skunk!

"), or AYYLU (" Not clearly coded, repeat more clearly .").

Code words were chosen for various reasons: length, pronounceability, etc.

Meanings were chosen to fit perceived needs: commercial negotiations, military terms for military codes, diplomatic terms for diplomatic codes, any and all of the preceding for espionage codes.

Codebooks and codebook publishers proliferated, including one run as a front for the American Black Chamber run by Herbert Yardley between the First and Second World Wars.

The purpose of most of these codes was to save on cable costs.

The use of data coding for data compression predates the computer era ; an early example is the telegraph Morse code where more-frequently used characters have shorter representations.

Techniques such as Huffman coding are now used by computer-based algorithms to compress large data files into a more compact form for storage or transmission.