Survey of LHarc and LHA versions and names

The LHarc family of software (including LHA, etc.) is an old compression and archiving utility, originally for DOS computers. I've found the LHarc version history to be confusing in a number of ways. In this post, I'll try to explain what's what, to the best of my knowledge. LHarc is comparable to its contemporaries PKZIP … Continue reading Survey of LHarc and LHA versions and names

Ambiguity of some infinite math expressions

I've come to realize that I don't actually know precisely how to interpret some infinite math expressions with an ellipsis ("…"), like $latex \sqrt{1 + \sqrt{1 + \sqrt{1 + \dots} } }$ First, to flatten out the syntax, I'll define $latex R$ to be the square root function: $latex R(x) = \sqrt{x}$. Now evaluate the … Continue reading Ambiguity of some infinite math expressions

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, … Continue reading Notes on PKLITE format, Part 3

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