C how to book histograms using CFBook package
   
-       PROGRAM EXAMPLE
 
        real f,rand        
        integer i       
        
  C book histograms
          CALL GBOOK1(1,"1D example",10,0D0,40D0)
          CALL GBOOK1(2,"1D again example",5,0D0,10D0)
          CALL GBOOK2(3,"2D example",10,0D0,1D0,10,0D0,5D0)
 
 
-         do i=1,1000
            f=MCPOI(10.0)
  C fill histogram with f
            call GF1(1,2D0*f)
            f=MCPOI(5.0)
  C fill another hitogram
             call GF1(2,0.2D0*f)
             f1=MCPOI(0.5)
             f2=MCPOI(2.0)
             call GF2(3,0.5D0*f1,0.5D0*f2)
          enddo
 
 
  C...Write  histograms to a XML file.
          Call GWRITE("fortran.xml")
 
          END