The Save command saves the current state of the program to a file with a .RFP filename extension. This file can later be recalled with the opensession command. All current information is saved, including the units, reference, properties, propertyorder and substance as well as all isopropertytables and plotwindow. You will be asked if you want to save when you exit the program if the 'Prompt to save session when closing' option is selected in the preferences.