/sys$common/syshlp/helplib.hlb FORTRAN, /CHECK, BOUNDS  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Enables or disables bounds checking.  If /CHECK=BOUNDS is
  specified, each dimension of an array reference or substring
  subscript reference is checked to determine whether it is within
  the range of the dimension specified by the array or character
  variable declaration.

  /CHECK=NOBOUNDS specifies no checking and presumes that no
  subscripts exceed their declared bounds.

  /CHECK=BOUNDS is not supported when /VECTOR or /PARALLEL=AUTOMATIC
  is in effect.