The expressions are inserted during the normal execution of a calculation using the keypad.
The numerical values​or operators included can be converted into variables (the value of which may be subsequently amended) or calculated items (for partial results).
Once you have completed entering the expression you can save it by associating it with a name and a description to help you understand its meaning.
Link : example : create an expression
The expressions are then saved as listed in order to be retrieved from time to time.
By pressing the button 
you can send an expression to a friend using AirDrop functionalities.
