@rem sets the process exit code to 1. should print "success!" actually prints nothing
cmd /c exit 1
if NOT ERRORLEVEL 0 echo success!

@rem prints "success!" as expected
cmd /c exit 1
if errorlevel 1 echo success!

@rem prints "failure!" even though the exit code is 0
cmd /c exit 0
if errorlevel 1 echo failure!

@rem prints "ERRORLEVEL=1" as expected
cmd /c exit 1
echo ERRORLEVEL=%ERRORLEVEL%