Histogram is a graph of the frequency distribution in which the vertical axis represents the count (frequency) and the horizontal axis represents the possible range of the data values. It is constructed from a frequency distribution, where choices on the § number of classes and class width have been made, To construct a histogram, rectangles or blocks are drawn on the x-axis (without any spaces between them) whose areas are proportional to the classes they represent. Histograms (and histographs) are used commonly where the subject item is discrete (such as the number of students in a school) instead of being continuous (such as the variations in their heights).