table continued character code space linefeed we use for and for the space we can' use or because they are prefixes for other characters what about -bit combinationsthere are eight possibilities and is and is why aren' any other combinations usedwe already know we can' use anything starting with or that eliminates four possibilities also is used at the beginning of and the linefeedand is used at the beginning of and only two -bit codes remainwhich we use for and in similar way we can see why only three -bit codes are available thusthe entire message is coded as for sanity reasons we show this message broken into the codes for individual characters of coursein reality all the bits would run togetherthere is no space character in binary messageonly and decoding with the huffman tree we'll see later how to create huffman codes firstwe'll examine the somewhat easier process of decoding suppose we received the string of bits shown in the preceding section how would we transform it back into characterswe can use kind of binary tree called huffman tree figure shows the huffman tree for the code just discussed the characters in the message appear in the tree as leaf nodes the higher their frequency in the messagethe higher up they appear in the tree the number outside each circle is the frequency the numbers outside non-leaf nodes are the sums of the frequencies of their children we'll see later why this is important how do we use this tree to decode the messagefor each character you start at the root if you see bityou go left to the next nodeand if you see bityou go right try it with the code for awhich is you go leftthen rightthen left againandmirabile dictuyou find yourself on the node this is shown by the arrows in figure