        1. Short DESCRIPTION.
    PPMD program is  file-to-file compressor, it  is written for  experimental
purposes mainly and it  is not intended for  immediate use.  I  was interested
in speed  and performance  improvements of  abstract PPM  model only,  without
tuning it  to particular  data types,  therefore compressor  works good enough
for texts,  but it is  not so  good  for nonhomogeneous files(executables) and
for  noisy  analog  data(sounds,  pictures  etc.).  Program  is  very   memory
consuming, You can choose balance between execution speed and memory  economy,
on one hand, and compression performance, on another hand, with help of  model
order selection option(-o).

        2. Distribution CONTENTS.
    MODEL.H, SUBALLOC.H, PPMDTYPE.H - header files;
    CODER.HPP, MODEL.CPP, SUBALLOC.CPP, PPMD.CPP - code sources;
    MAKEFILE.IMK - makefile for IntelC v.4.0;
    MAKEFILE.MAK - makefile for BorlandC v.5.01;
    MAKEFILE.WMK - makefile for WatcomC v.10.6;
    PPMD.EXE     - compressor itself;
    PPMD5.EXE    - the same executable, optimized for Intel Pentium(R);
    READ_ME.TXT  - this file;

        3. LEGAL issues.
    Michael  Schindler`s  rangecoder  implementation  is  redistributed  under
standard  GNU  GPL  v.2.  See  http://www.compressconsult.com/rangecoder/  for
further information.
    It is  strongly forbidden  to use  PPMD program  as spice  for pizza,  all
other things are allowed and welcomed ;-).

        4. DIFFERENCES between variants.
        Jun 13, 1999  var.A
    Initial release;
        Jun 30, 1999  var.B
    Arithmetic coder was changed to newer version;
    Simplified LOE was tested(MODEL1.CPP file);
    Some small improvements were done;
        Aug 22, 1999  var.C
    Rudimentary SEE was added;
    Some small improvements were done;
        Oct  6, 1999  var.D
    Inherited probabilities(IPs) were added;
    Memory requirements were reduced a bit;
    Small improvements were continued;
        Dec  3, 1999  var.E
    Program name was changed from PPM, escape method D(PPMD) to PPM by
Dmitry(PPMD). Pronounce correctly! ;-)
    Bug in ARI_FLUSH_ENCODER was crushed;
    MODEL1.CPP file was removed from package due to simplified LOE gives
negligible gain(full LOE implementation would give some gain);

        5. REFERENCES.
    Excellent  introductory  review  T.Bell,  I.H.Witten, J.G.Cleary 'MODELING
FOR TEXT COMPRESSION'. Russian translation is placed at
http://cotty.mebius.net/compress/ru/modeling.txt;
    Very descriptive M.R.Nelson`s COMP-2 program(PPMD is based on it).  COMP-2
is  in  wuarchive.wustl.edu:/mirrors/msdos/ddjmag/ddj9102.zip  (inner zip file
nelson.zip);
    P.G.Howard PhD thesis 'The Design and Analysis of Efficient Lossless Data
Compression Systems', is available in
ftp.cs.brown.edu/pub/techreports/93/cs93-28.ps.Z;
    S.Bunton PhD thesis 'On-Line Stochastic Processes in Data Compression',
is available in ftp.cs.washington.edu/tr/1997/03/UW-CSE-97-03-02.PS.Z;

    AUTHOR SHALL NOT BE LIABLE FOR ANY DIRECT, INDIRECT, SPECIAL,  INCIDENTAL,
OR CONSEQUENTIAL  DAMAGES ARISING  OUT OF  ANY USE  OF THIS  SOFTWARE. YOU USE
THIS PROGRAM AT YOUR OWN RISK.

                                        Glancy compression!
                                        Dmitry Shkarin
                                        E-mail: shkarin@arstel.ru
