Well, i'm not a expert in this area but i try explain you.
A Cron is a daemon running in your system that call any process you have configure at the time you have configure. The process call by Cron dont have a special type of programming.Start, make its work and end.
A daemon proccess is make for running all the time, and when "something" happens it makes a new thread that make the work.
L'essentiel est invisible pour les yeux.(Le petit prince)
What is essential is invisible to the eyes.(The Little Prince)
Lo esencial es invisible a los ojos. (El principito)
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com