•   In the absence of an explicit "as s#" clause, string arguments to functions and procedures, as well as the return value of a string function, now defaults to s0 (i.e. dynamic, unlimited) instead of the current STRSIZ.

•   STRSIZ 0 now sets the default string size to dynamic, as would be expected. Previously it set the default string size to a fixed length of zero, i.e. making it impossible for any unmapped string variable to hold a value.

•   SWITCH and CASE arguments are no longer limited by the current STRSIZ. Previously the compiler would complain about it you were forced to actually change the STRSIZ to accommodate them, which was not very programmer-friendly.

Note that all of the above are purely compiler adjustments, i.e. they change the resulting RUN programs, which are backward compatible as least as far back as 6.0.