Given a list of intervals and a number of points in each interval, such as is given by the output of the classes command, the histogram (or histogramme) command will draw a box over each interval so that the height of each box is proportional to the number of points and the total area of the boxes is 1. For example, if you enter
you will get
If you just give the histogram a list of numbers, or a list with values a and b, then you will get the histogram of the result of applying classes to the list. For example, if you enter
you will get