SimGen generates a file system_setup.do file that is invoked when the simulator is run from within XPS. The contents of the file contain the following:
alias c "do system.do; set xcmdc 1"
alias s "vsim -t ps system_conf; set xcmds 1"
What are set xcmdc 1 and set xcmds 1 used for in this file?
The xmdc and xmds variables are used by the helper scripts to keep track of whether you ran the "c" or "s" command, respectively. When the wave and list helper script commands are run, they check if these flags are set or not. A message is printed if "c" and "s" are not run (since the list and wave scripts would otherwise be referencing undefined signals).