NETPIC (Jim Tucker)

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File Format
Name NETPIC (Jim Tucker)
Ontology
Extension(s) .npx, others
Released 1995

NETPIC is a DOS utility developed by Jim Tucker. Its main feature is to convert a GIF image file to a COM file that, when executed, displays the image.

Discussion

The generated COM file can optionally use an ASCII-only encoding suitable for inclusion in an email. See Executable envelopes#Transfer-encoded executables for other executable formats of this sort.

Early versions (pre-v1.3) have a -w option to encode an arbitrary COM file in an ASCII-only format. Later, this feature was moved to a separate NETRUN utility.

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. Most versions have a -z option to omit the wrapper, producing a file that can be executed directly (though you may have to rename it to end in ".COM").

Versions 2.00+ include an NPX2GIF utility that converts an executable image file back to a GIF file.

Versions with the -w option also have a -e option, to recover the original binary COM file from an ASCII-encoded COM file.

Identification

(Based on limited research.)

Binary-encoded graphics files are observed to start with bytes f6 06 2f 01 ff 74 ?? ba 15 01 b4 09 cd 21 b4 07.

ASCII-encoded graphics files, without the wrapper, older 3→4 format, start with "NETPIC.COM" (which apparently is valid x86 machine code).

ASCII-encoded graphics files, without the wrapper, newer 4→5 format (default for v2.00+), start with "XPPPYZIQD". This does not distinguish them from NETSEND and some NETRUN files. Files made by NETPIC apparently have "NETPIC" at offset 47.

ASCII-encoded arbitrary COM files (-w option) start with "COM-PRG.COM". This does not distinguish them from older NETRUN files. Files made by NETPIC v1.0d have "NETPIC" at offset 520.

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