PPMd

PPMd (or PPMD) is a data compression scheme best suited to compression of text files.

"PPM" refers to the "Prediction by Partial Matching" class of compression algorithms, and the "d" is an arbitrary identifier for the specific algorithm.

Related formats

 * 7z format supports PPMd.
 * ZIP format supports PPMd (compression code 98), though application support for it is limited.

Links

 * Wikipedia: Prediction by partial matching