Library /sys$common/syshlp/basichelp.hlb Qualifiers, BOUNDS_CHECKING  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Tells BASIC to perform range checks on array subscripts.   BASIC  checks
  that all array references are within the array bounds set when the array
  was declared.

  Format

      [NO]BOUNDS_CHECKING