need command.com if not already there

command.com is required to run dos apps. this is not something the cmd shell can do. I could be wrong, but I think an NTVDM is started with command.com.

• if you are in a cmd shell and you execute a dos executable (an exe or .com or .bat that is not a windows PE), command.com is temporarily shelled out as a hidden child process to execute the dos program and uses the cmd shell's console window for output.
• dos programs may cause the console to switch to 80x25 or 80x50-line window and buffer for the rest of the cmd shell session.
• command.com can go full screen and take over the monitor with alt-enter. recovery afterwards to a cmd shell is not guaranteed.

this is what I have observed from using it.

http://jesusnjim.com/pc-repair/limitations.html
contains the limitations of the command line length and character set recognized by command.com (converts lowercase to uppercase). Note that it is more limited than cmd's.

I think the command-line length was 127 characters or 255 or 256 or soemthing like that, in windows 9x xcopy only recognized filepaths up to the first 64 characters, but this was fixed in xp I believe.

command.com has switches.
[[drive:]path] path to command.com
/E:nnnnn set env size to nnnnn bytes
/P make command.com permanent (can't exit)
/C string execute string through command.com then stop.
/MSG all error messages to be stored in memory. use this with /P