pro plothist,apre,bpre,prn,file=fnam
;pro plothist,apre,apost,bpre,bpost,prn,file=fnam

printer=['lp ','lp -dmdilj4 ']

if prn ne 0 then begin
  set_plot,'ps
  device,/land,bits=8,yoffs=10.75,xoffs=0.5,ysize=7.0,xsize=10.5,/in
  if keyword_set(file) then device,file=fnam & endif $
else begin
  set_plot,'x
endelse

!p.multi=[0,2,0]

xyouts,/norm,0,1.05,'DARK Histograms, Cold CCD (-23 C), Flight config. 20.12.93'

plot_io,apre,yran=[.1,1000000.],psym=10,$
  tit='Amplifier A',xtit='DN',ytit='Occurences'
;  tit='Amplifier A; solid: pre-zap, dashed: post-zap',xtit='DN',ytit='Occurences'
;oplot,apost,linestyle=1,psym=10

plot_io,bpre,yran=[.1,1000000.],psym=10,$
  tit='Amplifier B',xtit='DN',ytit='Occurences'
;  tit='Amplifier B; solid: pre-zap, dashed: post-zap',xtit='DN',ytit='Occurences'
;oplot,bpost,linestyle=1,psym=10

!p.multi=0

if prn ne 0 then begin
  device,/close
  if keyword_set(file) then fnam=fnam else fnam='idl.ps'
  spawn,printer(prn-1)+fnam
  set_plot,'x
endif

end