Notes on PKLITE format, Part 3

For an introduction, and a list of the other posts in this series, see Part 1. Code image compression format Prerequisites: This section assumes you already understand how to decode (non-adaptive) Huffman-coded (or "prefix-coded") data, and how to decompress LZ77-compressed data.Please at least read the notes near the end of Part 2 of this series, …

Notes on PKLITE format, Part 2

For an introduction to PKLITE, and a list of the other posts in this series, see Part 1. This post uses some of the EXE jargon defined in my post on DOS EXE format. Structure of PKLITE-compressed files Here's a bird's eye view of how PKLITE transforms a DOS EXE file when it compresses it: …

Notes on PKLITE format, Part 1

I've been writing (as a feature of Deark) a decompressor for DOS EXE files compressed with PKLITE. Before I forget it all, I decided to write down some of the things I've learned about PKLITE. This is the first post in a series. Other posts: Part 2Part 3(At least one more part is planned.) There …

A quick overview of DOS EXE file format

This is a brief introduction to, and a diagram of, the basic structure of the EXE executable file format used by MS-DOS and some other operating systems. DOS EXE is a subset of the PE "Portable Executable" format still used by Microsoft Windows today, so this also constitutes preliminary information that could be helpful to …

Testing some LZ77 compression limits

This post is about data compression algorithms that involve LZ77, or a similar kind of compression. It's mainly about old-school compression algorithms and software. There is some information about LZ77 in my post about LZ77 prehistory. I won't explain it in detail here, but here are some things to know about it. Both the compressor …

Ways things can rotate

This is an overview of some of the kinds of rotation an object can undergo, with a focus on astronomical objects. Standard warning: I'm starting to realize that I don't really know enough about physics to write about this. But I try not to let things like that stop me. Things to note: I'm discussing …

Differences between females and males

What statistical differences, in body and behavior, does science predict we might observe between females and males of the same species? It's not a safe topic for casual conversation, but it's one that I think is interesting. I'll consider whether it's plausible that such differences might exist, and if so, why. I'll try to keep …

The “guess what number I’m thinking of” problem

This post is, to some extent, a follow-up to my post on the two envelopes problem. As before, you're the subject of an experiment. Your adversaries, who I'll call "Team E", present you with two envelopes, each containing a slip of paper with a different number written on it. The numbers could be any (Real) …

ARC/PAK’s “Distilled” compression scheme

PAK is an old file compression and archiving program for DOS, developed by NoGate Consulting. (Search the web for "pak251.exe".) It has a number of features, which include some extensions to ARC format. One such ARC extension is compression method #11, named "Distilled". It was introduced in PAK v2.0, released in July 1989. Unlike my …

ARC’s “Trimmed” compression scheme

ARC is a file compression and archiving utility that was in use from the mid-1980s to the early 1990s, mainly on DOS computers. It was developed by a small company named System Enhancement Associates. The last major version of ARC was 7.x, first released in late 1989 or early 1990. In v7, ARC became part …