gnuplot algorithm to find axis spacing

[Daniel F. <boy...@gm...>]

Hello,

I want to understanding how gnuplot calculates xtic for a given range  
e.g.
plot x
set xrange [0:100]
replot

will place tic marks at 0, 20, 40, 60, 80 and 100.

Where is this calculated in the code?

How does gnuplot calculate the step size between tic marks?

I have worked on my own algorithm for xtics position for a given  
range and it works well.  However it required the user to input the  
step size between tic marks. e.g. plotting x from 0 to 100 the user  
would have to specify the tic separation was 20.

Regards,

Daniel.