VMS Help FORTRAN, Format Specifiers, SP  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  (Always + Signs)

  Causes the processor to produce a leading plus character (+) in any
  position where this character would otherwise be optional.

  This descriptor affects all (suppress + signs) fields that follow
  it, until an S or SS is encountered.  The SP descriptor affects all
  following I, F, E, D, and G editing (in the same FORMAT statement)
  during the execution of an output statement.