If HCOMPA have not been called, a 1-dimensional
histogram is scaled so that its maximum is at 90% of the available height.
This maximum takes into account the HBOOK ``functions'' (if any) and error
bars (if any). This can be changed with parameter HMAX in HPLSET (default
value for HMAX is 0.9).
HPLOT always plots histograms from zero to the maximum (unless the minimum
is negative). This differs from HBOOK which prints from the minimum to the
maximum. This is not a serious problem, since the actual value of the
contents is available with HBOOK, but HPLOT could produce a bin appearing
to have zero contents when in fact it contains a very small value.
When the logarithmic scale in X is requested for a 1-dim histogram only
the axe are drawn, not the contour.