VMS Help BASIC, /SINGLE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

   The /SINGLE qualifier specifies that floating-point variables  are  single
   precision.   This  qualifier  is  present  for compatibility with previous
   versions of VAX BASIC.  You should use the /REAL_SIZE qualifier to specify
   the precision of floating-point variables.