Notes on PKLITE format, Part 7: v1.20 compression

This is a continuation of my series on PKLITE executable compression format for DOS. For a list of other posts, see the first post. In particular, Part 3 is an important prerequisite. In a previous post, I named a then-unknown compression scheme "PKLC-U". In this post, I'll call it "v1.20 compression". I'll refer to all … Continue reading Notes on PKLITE format, Part 7: v1.20 compression

ColoRIX compressed 16-color format

This is a follow-up to my previous post on ColoRIX compressed 256-color images. Here I'll explain how to decode (at least some) compressed 16-color images. The short answer: The compression for 16-color images is the same as for 256-color images, except that the "XOR filter" step doesn't happen. The documentation for "RIX3" format (or "new" … Continue reading ColoRIX compressed 16-color format

Updated survey of LHarc and LHA

Since my first post on DOS versions of LHarc/LHA, I've found a few more versions of the software. Six of them appear to be original/official, and all of those are Japanese-language: 1.13d, 2.05b, 2.13, 2.52, 2.54, and 2.55. And I found quite a few new modified or hacked versions, two of which I'll discuss: "v1.14a" … Continue reading Updated survey of LHarc and LHA

Survey of EXPAND/DECOMP utilities

If you look at old DOS and Windows software distribution disks, you may see a lot of files whose names have the last character replaced by a "_" character, or sometimes a "$" character. For example: mplayer.ex_ mplayer.hl_ mplayer.re_ msacm.dl_ msacm.dr_ msadpcm.ac_ mscomstf.dl_ ... Many such files belong to a family of compressed file formats … Continue reading Survey of EXPAND/DECOMP utilities

Notes on PKLITE format, Supplement 1: Descrambling

This post is part of a series about PKLITE format. For a list of all the posts, see the first post. In a previous post, I noted that some PKLITE-compressed executable files are more difficult to deal with, because most of the decompressor is obfuscated. I named the obfuscation format "scrambled". In this post, I'll … Continue reading Notes on PKLITE format, Supplement 1: Descrambling

Which comes first in DOS timestamps, the date or the time?

There are a lot of old DOS-centric file formats, especially file archiving and compression formats, which store timestamps of files. Most of them use the standard MS-DOS timestamp format for such things. This format is usually interpreted as two 16-bit integers: one for the date, and one for the time of day. I'm not sure, … Continue reading Which comes first in DOS timestamps, the date or the time?