I can understand cmd but not /c. I was trying to invoke a java program from the current for which I use Runtime.getRuntime().exec("cmd /C java helloworld") There arises my doubt.
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            /C Carries out the command specified by the string and then terminates
You can get all the cmd command line switches by typing cmd /?
                  Simon Temlett
                   2009-02-05 10:26:34
                
              
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            CMD.exe
Start a new CMD shell
Syntax CMD [charset] [options] [My_Command]
Options
/C Carries out My_Command and then terminates
From the help.
                  Andrea Ambu
                   2009-02-05 10:28:24
                
              
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            The part you should be interested in is the /? part, which should solve most other questions you have with the tool.
Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.
C:\>cmd /?
Starts a new instance of the Windows XP command interpreter
CMD [/A | /U] [/Q] [/D] [/E:ON | /E:OFF] [/F:ON | /F:OFF] [/V:ON | /V:OFF]
    [[/S] [/C | /K] string]
/C      Carries out the command specified by string and then terminates
/K      Carries out the command specified by string but remains
/S      Modifies the treatment of string after /C or /K (see below)
/Q      Turns echo off
/D      Disable execution of AutoRun commands from registry (see below)
/A      Causes the output of internal commands to a pipe or file to be ANSI
/U      Causes the output of internal commands to a pipe or file to be
        Unicode
/T:fg   Sets the foreground/background colors (see COLOR /? for more info)
/E:ON   Enable command extensions (see below)
/E:OFF  Disable command extensions (see below)
/F:ON   Enable file and directory name completion characters (see below)
/F:OFF  Disable file and directory name completion characters (see below)
/V:ON   Enable delayed environment variable expansion using ! as the
        delimiter. For example, /V:ON would allow !var! to expand the
        variable var at execution time.  The var syntax expands variables
        at input time, which is quite a different thing when inside of a FOR
        loop.
/V:OFF  Disable delayed environment expansion.