CALC 1 has 2 ways of storing and recalling numbers, using the and keys, and an automatic stack.
The key copies the value from the x register into a storage variable. Storage variables a-z are general purpose user variables.
Also, depending on the calculator, other values for that calculator can be stored.
The key copies the value from the storage variable into the x register.
When entering a formula, the variables can be used in the formula by tapping followed by the variable key.
The results of a formula can be stored in a variable by tapping "var name" , followed by the formula.
The financial calculators have variables that they use to store the interest rate, present value and so on. These begin with "fv".
Each conversion calculator has a variable to store the value be converted in the standard SI unit. These begin with "cn"
Using the "long press" gesture will display a hint about any key. (Video: Displaying a hint) You can inspect the Key Details to see the formulas and functions for any key.