VMS Help FORTRAN, Data, Types, COMPLEX  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Real and complex numbers are floating-point representations.

  COMPLEX*8 (F_floating) data is eight contiguous bytes aligned on an
  arbitrary byte boundary.  The low-order four bytes contain REAL*4
  data that represents the real part of the complex number.  The
  high-order four bytes contain REAL*4 data that represents the
  imaginary part of the complex number.

  COMPLEX*16 (D_floating) data is 16 contiguous bytes aligned on an
  arbitrary byte boundary.  The low-order bytes contain REAL*8
  (D_floating) data that represents the real part of the complex
  data.  The high-order eight bytes contain REAL*8 (D_floating) data
  that represents the imaginary part of the complex data.

  COMPLEX*16 (G_floating) data is 16 contiguous bytes aligned on an
  arbitrary byte boundary.  The low-order bytes contain REAL*8
  (G_floating) data that represents the real part of the complex
  data.  The high-order eight bytes contain REAL*8 (G_floating) data
  that represents the imaginary part of the complex data.