For historical reasons, the MZ is interpreted as the header of a 16-bit executable. When you run something under CMD (hopefully I'm getting this right, it's been a few years) it first runs it using the CreateProcess API, which just tries to run the file as an executable, regardless of extension, then it falls back to ShellExecute if it doesn't have an MZ header, which dispatches based on extension.
Basically you get a dialog saying the text file isn't a compatible executable. If you change the MZ to anything else, it opens in notepad.
Windows 7 64 bit here - it just has the error message box, and the same text in the cmd window, it doesn't open the file though :)
"This version of foo.txt is not compatible with the version of Windows you're
running. Check your computer's system information to see whether you need a
x86 (32-bit) or x64 (64-bit) version of the program, and then contact
the software publisher."
That's because it's treating it as a 16-bit DOS executable (since it has the 'MZ' magic number but not the rest of the PE header that tells Windows that it's 32 or 64-bit). 64-bit Windows can't run 16-bit executables at all.
32-bit Windows should fail a little later in the execution process; it can run 16-bit software, but your text file is missing the rest of the MZ-format header.
[fred@dejah launch]$ chmod +x foo.txt
[fred@dejah launch]$ ./foo.txt
fixme:winediag:start_process Wine Staging 1.9.12 is a testing version containing experimental patches.
fixme:winediag:start_process Please mention your exact version when filing bug reports on winehq.org.
winevdm: Cannot start DOS application E:\launch\foo.txt
because the DOS memory range is unavailable.
You should install DOSBox.
[fred@dejah launch]$
I have Wine installed. Same defect as Windows, which is either good or bad -- this is hard to determine.
At least, the hint of installing DOSBox is reasonable. So, let's do that:
[fred@dejah launch]$ sudo dnf install dosbox
and try it again:
[fred@dejah launch]$ ./foo.txt
fixme:winediag:start_process Wine Staging 1.9.12 is a testing version containing experimental patches.
fixme:winediag:start_process Please mention your exact version when filing bug reports on winehq.org.
DOSBox version 0.74
Copyright 2002-2010 DOSBox Team, published under GNU GPL.
---
ALSA lib pulse.c:243:(pulse_connect) PulseAudio: Unable to connect: Connection refused
CONFIG: Generating default configuration.
Writing it to /home/fred/.dosbox/dosbox-0.74.conf
CONFIG:Loading primary settings from config file /home/fred/.dosbox/dosbox-0.74.conf
CONFIG:Loading additional settings from config file /home/fred/.wine/dosdevices/c:/users/fred/Temp/cfgcbaf.tmp
MIXER:Can't open audio: No available audio device , running in nosound mode.
ALSA:Can't subscribe to MIDI port (65:0) nor (17:0)
MIDI:Opened device:none
[fred@dejah launch]$
