If Command Extensions are enabled IF changes as follows: IF /I string1 compare-op string2 command IF CMDEXTVERSION number ...

If Command Extensions are enabled IF changes as follows:        IF [/I] string1 compare-op string2 command      IF CMDEXTVERSION number command      IF DEFINED variable command    where compare-op may be one of:        EQU - equal      NEQ - not equal      LSS - less than      LEQ - less than or equal      GTR - greater than      GEQ - greater than or equal    and the /I switch, if specified, says to do case insensitive string  compares.  The /I switch can also be used on the string1==string2 form  of IF.  These comparisons are generic, in that if both string1 and  string2 are both comprised of all numeric digits, then the strings are  converted to numbers and a numeric comparison is performed.    The CMDEXTVERSION conditional works just like ERRORLEVEL, except it is  comparing against an internal version number associated with the Command  Extensions.  The first version is 1.  It will be incremented by one when  significant enhancements are added to the Command Extensions.  CMDEXTVERSION conditional is never true when Command Extensions are  disabled.    The DEFINED conditional works just like EXISTS except it takes an  environment variable name and returns true if the environment variable  is defined.