Program example; logistic map

Normally, PostScript code is generated by a program (although one can also program simple illustrations directly by hand). Below is a link to a Fortran 90 program that produces a graph of the logistic map, as described in the comments in the beginning of the program. Two graphs produced by this program are also shown (converted from ps to gif), along with the input data used. 
logistic.f90
Input data in the file 'read.in': 
3.0   4.0  0.0  1.0
1000 1000  200
Input data in the file 'read.in': 
3.82   3.87  0.4  0.6
1000 1000  200