[[Refer to [Microsoft] documentation.]]

MS-DOS shell built-in command called with a filename that invokes the executable associated with the filename's extension. Acts about like double-clicking on a file in File explorer. Usage example from Tcl:

 eval exec [auto_execok start] "" [list [file nativename $filename]]

which, if filename ends e.g. in .htm, calls up IE (if that's your default browser); Win Word for .doc, etc.

Nits: 

   * If the first parameter is quoted, "start" will take it for a window title.  Add an empty string to avoid the problem.

   * COMMAND.COM, CMD.EXE and the DOS command-line tools misunderstand "/" in filenames.  Use [[file nativename]] to cure that.

[[Use in [invoking browsers].]]

To launch a [Windows] application (such as [Tk]) from a
[console application] (such as [Tcl]) 
in such a way that it returns only after the subprocess
has terminated, use
      start /w wish83 myapp.tcl

----

As with most Windows command-line tools, see "start /?" from a command prompt
for built-in help.

----

[schlenk] One caveat usually found the hard way, is the simple fact, that Microsoft found it amusing to implement start differently on Win9x and on Win2k/XP. So read its documentation before you use it. Try to start something like this on W95 and W2k an see what happens:
 start "c:\program files\tcl\bin\wish84" myapp.tcl
Hint (this works on W2k):
 start "" "c:\program files\tcl\bin\wish84" myapp.tcl

----
[[what category]]