Editing LZ77 and LZ78 (section)

===Implementations===
Even though all LZ77 algorithms work by definition on the same basic principle, they can vary widely in how they encode their compressed data to vary the numerical ranges of a length–distance pair, alter the number of bits consumed for a length–distance pair, and distinguish their length–distance pairs from ''literals'' (raw data encoded as itself, rather than as part of a length–distance pair). A few examples:
* The algorithm illustrated in Lempel and Ziv's original 1977 article outputs all its data three values at a time: the length and distance of the longest match found in the buffer, and the literal that followed that match. If two successive characters in the input stream could be encoded only as literals, the length of the length–distance pair would be 0.
* [[Lempel–Ziv–Storer–Szymanski|LZSS]] improves on LZ77 by using a 1-bit flag to indicate whether the next chunk of data is a literal or a length–distance pair, and using literals if a length–distance pair would be longer.
* In the PalmDoc format, a length–distance pair is always encoded by a two-byte sequence. Of the 16 bits that make up these two bytes, 11 bits go to encoding the distance, 3 go to encoding the length, and the remaining two are used to make sure the decoder can identify the first byte as the beginning of such a two-byte sequence.
* In the implementation used for many games by [[Electronic Arts]],<ref>{{cite web
| url=http://wiki.niotso.org/QFS_compression
| title=QFS Compression (RefPack)
| work=Niotso Wiki
| access-date=2014-11-09}}</ref> the size in bytes of a length–distance pair can be specified inside the first byte of the length–distance pair itself; depending on whether the first byte begins with a 0, 10, 110, or 111 (when read in [[Endianness|big-endian]] bit orientation), the length of the entire length–distance pair can be 1 to 4 bytes.
* {{As of|2008}}, the most popular LZ77-based compression method is [[DEFLATE]]; it combines LZSS with [[Huffman coding]].<ref>{{cite web
| url=https://www.zlib.net/feldspar.html
| title=An Explanation of the Deflate Algorithm
| first=Antaeus
| last=Feldspar
| date=23 August 1997
| work=comp.compression [[Usenet newsgroup|newsgroup]]
| publisher=zlib.net
| access-date=2014-11-09}}</ref> Literals, lengths, and a symbol to indicate the end of the current block of data are all placed together into one alphabet. Distances can be safely placed into a separate alphabet; because a distance only occurs just after a length, it cannot be mistaken for another kind of symbol or vice versa.