The HISTOGRAM statement creates a histogram for the analysis variable Exponential_x. The EXP option superimposes a fitted density curve for an exponential distribution . The FILL option specifies to fill the area under the exponential density curve with the CFILL= color. The L= option specifies a distinct line type for the density curve. The MIDPOINTS= option specifies a list of values to use as bin midpoints. 
   histogram /exp(fill l=3) cfill=yellow midpoints=.05 to 5.55 by .25;