This scheme is initiated by Ziv and Lempel [1]. A slightly modified version is described by Storer and Szymanski [2]. An implementation using a binary tree is proposed by Bell [3]. The algorithm is quite simple: Keep a ring buffer, which initially contains \"space\" characters only. Read several letters from the file to the buffer. Then search the buffer for the longest string that matches the letters just read, and send its length and position in the buffer.