C:\Documents and Settings\Owner>shutdown /?
Usage: shutdown [-i | -l | -s | -r | -a] [-f] [-m \\computername] [-t xx] [-c "comment"] [-d up:xx:yy]

        No args                 Display this message (same as -?)
        -i                      Display GUI interface, must be the first option
        -l                      Log off (cannot be used with -m option)
        -s                      Shutdown the computer
        -r                      Shutdown and restart the computer
        -a                      Abort a system shutdown
        -m \\computername       Remote computer to shutdown/restart/abort
        -t xx                   Set timeout for shutdown to xx seconds
        -c "comment"            Shutdown comment (maximum of 127 characters)
        -f                      Forces running applications to close without warning
        -d [u][p]:xx:yy         The reason code for the shutdown
                                u is the user code
                                p is a planned shutdown code
                                xx is the major reason code (positive integer less than 256)
                                yy is the minor reason code (positive integer less than 65536)

system("SHUTDOWN");

system("SHUTDOWN/s");

#include <stdio.h>

void main(void) {
  cout << "Now shutting down..."
  system("shutdown /s");
}