DOC2COM (Gerald DePyper)

Revision as of 18:34, 22 August 2024

DOC2COM is a DOS utility for creating a COM file that, when executed, displays a text document in a full-screen viewer. It was developed by Gerald (Jerry) DePyper.

When viewing a document, press F1 for help. Sometimes there is a function (Alt-F) to write the text to a file, but it depends on the DOC2COM version, and the options used when creating the file.

Format details

Starting with v1.3, the embedded text is usually encrypted (obfuscated).

To de-obfuscate, XOR each obfuscated byte with the obfuscated byte following it, or with 0xff for the very last byte.

Identification

(To identify a generated file...)

Version 1990-04-03: The first 16 bytes are:

be 5e 04 b9 18 00 e8 b2 01 e2 fb 3b 36 54 04 72

Version 1990-12-01: The first 16 bytes are:

be 62 04 b9 18 00 e8 b2 01 e2 fb 3b 36 58 04 72

v1.2: The first 16 bytes are:

fc be 50 0b b9 18 00 e8 2f 02 e2 fb 3b 36 46 0b

v1.3+: Files start with the byte pattern:

fc ?? ?? ?? ?? 49 8b 36 ?? ?? 8b fe ac 32 04 aa
e2 fa ac 34 ff aa ...

For v1.3+, the byte at offset 1 is 8b if encrypted, or eb if not encrypted.

Software

• DOC2COM
  • Unversioned 1990-04-03 release: DOC2COM.ZIP
  • Unversioned 1990-12-01 release: DOC2CO.ZIP
  • v1.2 (1991-04-14): DOC2CM12.ZIP
  • v1.3[1992-06-27 release]: doc2com3.zip
  • v1.3[1993-05-21 release]: DOC2COM.ZIP
  • v1.31 (1994-05-18): DOC2COM.ZIP
  • v1.40 (1995-06-05): DOC2COM.ZIP

Sample files

• readut.zip → readme.com (1990-04-03)
• BOLO1.ZIP → README.COM (1990-12-01)
• GREYHND.ZIP → README.COM (v1.20)
• NBIRD20.ZIP README.COM (1.3x)
• B2S10.ZIP → README.COM (1.40)
• Voyeur → /DEMOS.COM, /README.COM (unknown version)
• dexvert samples — document/doc2comGerald