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 … Continue reading A quick overview of DOS EXE file format

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 … Continue reading Testing some LZ77 compression limits

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 … Continue reading Differences between females and males

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) … Continue reading The “guess what number I’m thinking of” problem

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 … Continue reading ARC/PAK’s “Distilled” compression scheme

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 … Continue reading ARC’s “Trimmed” compression scheme

Win32 I/O character encoding supplement 2 – setlocale enhancement

This is part of a series of post on using Unicode in Windows command-line applications. Here's the first post. Sometime in 2018, some functions in the Windows 10 C runtime system, and related development SDKs, were enhanced to support UTF-8. This feature is enabled by calling the setlocale function. For reference, Microsoft's current documentation of … Continue reading Win32 I/O character encoding supplement 2 – setlocale enhancement

Making an uncompressed JPEG 2000 file

Challenge: Construct a JPEG 2000 image file that isn't compressed. Also, try to do it without spending any money. Overview The flagship feature of the JPEG 2000 suite of graphics formats is the wavelet-based "JPEG 2000 codestream" compression format. This challenge is not to figure out how to make a degenerate form of that format … Continue reading Making an uncompressed JPEG 2000 file