Ronni Coppins, age 12, of Marietta, Ga., for her question:

WHAT IS CRYPTOGRAPHY?

Almost every school age boy or girl has played at cryptography at one time or another. And if you have ever had a classroom note intercepted by an unappreciative teacher, you realize its value. The word "cryptography" comes to us from Greek words for "hidden" and "writing." Of course by now you have guessed that cryptography deals with codes and ciphers and secret messages. The art is as old as writing itself and can be traced back thousands of years to the earliest days of civilization.

Codes can be as easy or as complicated as the writer wishes to make them. Naturally the person receiving the code must have a key to help him unlock the message. When Julius Caesar sent coded messages to his generals he used a simple substitution code. His generals knew that each letter of the coded text was actually three letters to the left in the normal alphabet. The letter F was decoded as C, and the letter G would be decoded as D. Modern codemakers use computers and super complicated mathematical systems in an attempt to keep messages secret.