The I Ching is made up of 64 symbols, or hexagrams, which are the binary combinations of six whole or broken ("changing") lines.  A hexagram contains a main text and six small ones, one for each line.  By manipulating three coins or forty-nine yarrow stalks according to a randomizing principle, the texts of two hexagrams are combined, producing one out of 4096 possible texts.  This contains the answer to a question the user has written down in advance (for example, "How much rice should I plant this year?").