Com2txt

Latest revision as of 13:25, 30 July 2024

Com2txt is a utility that converts a DOS COM file to one whose bytes all belong to a certain set of ASCII characters, and which still has the same functionality. It was developed by Naoyuki Nide. Most of the information about it is in Japanese.

It's a silly hack, but it had some practical uses, such as for embedding a COM file in a Batch file, email, etc.

It has a -r option, to recover the original file.

[edit] Disambiguation

Not to be confused with Com2txt (Dark Stalker).

For other software with a similar name or function, see Executable envelopes#Transfer-encoded executables.

[edit] Identification

Only version 1.11 has been evaluated. It can decode three formats, which we'll call old, new-default, and new-alternate.

Old files (e.g. from v1.00) start with "TXPPP".

New-default files (e.g. from v1.11) start with a roughly 200-byte prefix that begins "T_OOWW3=XXWX" (see the HDR_DATA.C source file). The signature "com2txt/Nide" also appears in the standard prefix, but is less reliable for format identification.

New-alternate format is enabled with the -c option (undocumented in English). It is named something like "com-batch shared format". The format begins ":=%00%AA5$QP".

GetTyp reports the existence of several newer versions of Com2txt, through v1.41. According to its database, files from v1.20-1.41 start the same way as v1.03-1.12, with "T_OOWW3=XXWX", but then they diverge.

[edit] Software

• com2txt v1.11 (DOS binary + source code)
  • A copy at GitHub

[edit] Sample files

• xpa167m.zip → *.COM (files have a customized signature)
• dexvert samples — archive/com2txtPacked