The default length gnuplot uses for tics is a little small, and makes the minor tics all but disappear on small plots. Naturally, the tic size can be adjusted at will. The following figure employs longer tic marks than we have seen so far:
Following is an example showing how to specify the length of the tic marks. The output of this script is the previous figure:
set tics scale 3
set mxtics 4
set mytics 4
plot [0:4*pi] sin(x)/x
The first (highlighted) code line sets the length of the tic marks to be three times the default length. The actual length may vary somewhat between terminals, so you may need to experiment to get the exact effect that you desire.