Queries about use of maxima



1  I have discovered that
   2.3b5    2.3d5     2.3e5     2.3s5
   2.3B5    2.3D5     2.3E5     2.3S5
all evaluate to 230000, and I have discovered many, many other 
descriptions in the Maxima help file, but I can find no explanation
of these operators b,d,e,s,B,D,E,S.  Why is there no entry under these
single letters in the Help index?  Where is there an explanation of
them?
2    Why does 'implicit_plot' not accept style specifications as for
plot2D?
3    Is it possible, other than manually, to constrain the axes of a
plot so that a circle resembles a circle, not an ellipse?
      Your assistance please.
             J. F. Ogilvie