Program to numerically solve 3 ODE's

Hello All,
Just to update you, I finished the program and submitted it. It works great! With all of your help it really made it much easier for me. Thank you.
Only thing I didn’t resolve which was not necessary, if entered a value for f"(0) which was too large I got NaN errors in the output file. I assume those are negative infinity errors due to DP numbers getting so large, but not really sure. I just instruct the user to input closer values.
If you have any comments on the NaN errors I would appreciate it.
If there are any questions about the program please let me know. FORTRAN is a very powerful tool, I’m glad I was forced to revisit it. Looking forward to another project I can use it on…
Kind regards,
Rick