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copied!<p>Here is a compilation of verified information from the various answers and cited references in this thread:</p> <ol> <li><code>command.com</code> is the 16-bit command processor introduced in MS-DOS and was also used in the Win9x series of operating systems.</li> <li><code>cmd.exe</code> is the 32-bit command processor in Windows NT (64-bit Windows OSes also have a 64-bit version). <code>cmd.exe</code> was never part of Windows 9x. It originated in OS/2 version 1.0, and the OS/2 version of <code>cmd</code> began 16-bit (but was nonetheless a fully fledged protected mode program with commands like <code>start</code>). Windows NT inherited <code>cmd</code> from OS/2, but Windows NT's Win32 version started off 32-bit. Although OS/2 went 32-bit in 1992, its <code>cmd</code> remained a 16-bit OS/2 1.x program.</li> <li>The <code>ComSpec</code> env variable defines which program is launched by <code>.bat</code> and <code>.cmd</code> scripts. (Starting with WinNT this defaults to <code>cmd.exe</code>.)</li> <li><code>cmd.exe</code> is backward compatible with <code>command.com</code>.</li> <li>A script that is designed for <code>cmd.exe</code> can be named <code>.cmd</code> to prevent accidental execution on Windows 9x. This filename extension also dates back to OS/2 version 1.0 and 1987.</li> </ol> <p>Here is a list of <code>cmd.exe</code> features that are not supported by <code>command.com</code>:</p> <ul> <li>Long filenames (exceeding the 8.3 format)</li> <li>Command history</li> <li>Tab completion</li> <li>Escape character: <code>^</code> (Use for: <code>\ & | > < ^</code>)</li> <li>Directory stack: <code>PUSHD</code>/<code>POPD</code></li> <li>Integer arithmetic: <code>SET /A i+=1</code></li> <li>Search/Replace/Substring: <code>SET %varname:expression%</code></li> <li>Command substitution: <code>FOR /F</code> (existed before, has been enhanced)</li> <li>Functions: <code>CALL :label</code></li> </ul> <p>Order of Execution:</p> <p>If both .bat and .cmd versions of a script (test.bat, test.cmd) are in the same folder and you run the script without the extension (test), by default the .bat version of the script will run, even on 64-bit Windows 7. The order of execution is controlled by the PATHEXT environment variable. See <a href="https://stackoverflow.com/questions/605101/order-in-which-command-prompt-executes-files-with-the-same-name-a-bat-vs-a-cmd-v">Order in which Command Prompt executes files</a> for more details.</p> <p>References:</p> <ul> <li><a href="http://www.ss64.com/ntsyntax/" rel="noreferrer">cmd.exe</a></li> <li><a href="http://gregvogl.net/courses/os/handouts/doscmdref.pdf" rel="noreferrer" title="PDF">command.com</a></li> </ul> <p>wikipedia: <a href="http://en.wikipedia.org/wiki/Comparison_of_computer_shells" rel="noreferrer">Comparison of command shells</a></p>

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