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

  INFORMATION - The total storage preceding  a  numeric  variable  in  a
  COMMON  or  MAP  is  an  odd  number  of bytes.  BASIC-PLUS-2 pads the
  preceding storage with a blank byte because  PDP-11  systems  requires
  that  numeric  data  start on a word boundary.  BASIC does not pad the
  storage because numeric data can start on any byte boundary.  However,
  if  you  want  the  program to run on both types of system, you should
  ensure that all numeric data starts on a word boundary.