The compression symbol, which is an index into the dictionary, locates that index's dictionary entry. The symbol represents a character string of up to 260 characters. If the entry is an unpreceded entry, the expansion process places at offset 0 from the current processing point the characters designated by that entry. Note that the first 256 correspond to the 256 possible values of a byte and are assumed to designate only the single character with that byte value.
If the entry is a preceded entry, the expansion process places the designated characters at the specified offset from the current processing point. It then uses the information in that entry to locate the preceding entry, which may be either an unpreceded or a preceded entry, and continues as described previously.
The sibling descriptor extension entries described earlier are also physically located within the expansion dictionary.