set style fill solid
set grid
#
#  Plot column 1 versus column 2, using bars that are 90% wide, 
#  and using column 3 as a label.
#
plot "grades_count.txt" using 1:2:(0.90):xtic(3)
#
#  I want the plot to include the full range of data.
#  So I specify the desired x range [xmin,xmax] and y range [ymin,ymax].
#
[0:4] [0:20] "grades_count.txt" using 1:2:(0.90):xtic(3)
#
#  The first and last bars actually extend out of the X range I specified.
#  Fix that.
#
plot [-1:5] [0:20] "grades_count.txt" using 1:2:(0.90):xtic(3)
#
#  All done.
#
quit