Welcome to Mathcad. What you have for the first 30 days is a full version of Mathcad (I assume Prime 6.0.) After 30 days (unless you've paid,) it will default to Express. PTC allows Express to run without a license indefinitely; but many of the functions will no longer work. If you open a file that has these functions you can see what the file looked like when it was saved (with all of the functions evaluated.) If you try to change anything in that file (or recalculate it) all of the premium functions will fail. (You basically have a "reader.") But even in Express, there is a fair amount of computing capacity.
Enjoy!
