NETRUN

NETRUN is a DOS utility that creates ASCII-only COM files, suitable for inclusion in an email message. It was developed by Jim Tucker. It is a spin-off of NETPIC.

See Executable envelopes for other executable formats of this sort.

Discussion
NETRUN features:
 * Convert a COM file to an ASCII-only COM file that runs like the original.
 * Convert an EXE file to an ASCII-only COM file that, when executed, writes the original EXE file to a temporary disk file, then executes it. Only small EXE files are supported.
 * Old versions (e.g. 2.2a) have a "self-extracting file" option . It produces an ASCII-only COM file that, when executed, writes the original (generally non-executable) file to disk. Later, this feature was moved to a separate NETSEND utility.

The ASCII-encoded files are normally wrapped in some plain text instructions, telling you to use a text editor to save the payload data to a .COM file. There is a  option to omit the wrapper, producing a file that can be executed directly (though you may have to rename it to end in ".COM").

Identification
Ignoring any wrapper, files made by older versions (e.g. 2.2a) start with "". This does not distinguish them from some files made by NETPIC (v1.0 with  option). For NETRUN v2.2a, "" appears at offset 151.

Ignoring any wrapper, files made by newer versions (e.g. 3.10) begin with "". This does not distinguish them from NETSEND and some NETPIC files. It's not clear how to reliably do that. For v3.10, at least, "" appears at offset 128.

Software

 * Simtel MSDOS May 1995 → Disc 2 → DISC2/DECODE/NETRUN22.ZIP - NETRUN v2.2a
 * [ NETRUN v3.10] (a.k.a. v3.1)