LDArc and LDIFF

LDArc (also written LDarc), and its successor LDIFF (also written LDiff), are differential compression utilities for DOS, designed for binary files. They were developed by Kazuhiko Miki (also known for LArc).

There are at least three different versions of their native .LZD file format:
 * The "lz6" format created by LDArc v1.00-1.03.
 * The "LD6" format created by LDIFF v1.10-1.20.
 * The format created by LDIFF v2.00.

LDIFF v2.00 can also create self-running patches in COM format.

The "lz6" and "LD6" formats are similar to LHA, but not really compatible with it.

Identification
LDArc v1.00-1.03 files have ASCII "" at offset 2.

LDIFF v1.10-1.20 files have ASCII "" at offset 2.

LDIFF v2.00 files apparently have ASCII "" at offset 4. They end with bytes.

COM files made by LDIFF v2.00 apparently have ASCII "" at offset 1021. The embedded LZD file starts at offset 1177.

Specifications

 * LDIFF v2.00 format is described in the included ldiff.man file (in Japanese).

Software

 * - Includes LDArc v1.00, and patches to create v1.01, v1.02, v1.03.
 * - Includes LDArc v1.00, and patches to create v1.01, v1.02, v1.03, and LDIFF v1.10.
 * - Same as above, packaged differently.
 * LDIFF v2.00 (Japanese): FreeWare Collection 2 → FreeSoftwareCollection2pd199x-jp.img → ms_dos/ldiff/ (or )
 * LDIFF v2.00 (Japanese): FreeWare Collection 2 → FreeSoftwareCollection2pd199x-jp.img → ms_dos/ldiff/ (or )

Sample files

 * → *.LZD ("lz6" format)