C:\WINDOWS>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)